Perf: improved discussions MFE's components re-rendering and loading time (#513)

* chore: configure WDYR for react profiling

* perf: reduced post content re-rendering

* perf: post content view and it child optimization

* perf: add memoization in post editor

* perf: add memoization in postCommnetsView

* perf: improved endorsed comment view rendering

* perf: improved re-rendering in reply component

* fix: uncomment questionType commentsView

* fix: removed console errors in postContent area

* perf: reduced postType and postId dependancy

* perf: improved re-rendering in discussionHome

* perf: improved re-rendering of postsList and its child components

* perf: improved re-rendering of legacyTopic and learner sidebar

* fix: postFilterBar filter was not updating

* fix: resolve duplicate comment posts issue

* fix: memory leaking issue in comments view

* fix: duplicate topic posts in inContext sidebar

* perf: add lazy loading

* chore: remove WDYR configuration

* fix: alert banner padding

* chore: update package-lock file

* fix: bind tour API call with buttons

package-lock.json

@@ -26,7 +26,6 @@
         "raw-loader": "4.0.2",
         "react": "16.14.0",
         "react-dom": "16.14.0",
-        "react-mathjax-preview": "2.2.6",
         "react-redux": "7.2.6",
         "react-router": "5.2.1",
         "react-router-dom": "5.3.0",
@@ -22327,19 +22326,6 @@
         "react": ">=16.8.0"
       }
     },
-    "node_modules/react-mathjax-preview": {
-      "version": "2.2.6",
-      "resolved": "https://registry.npmjs.org/react-mathjax-preview/-/react-mathjax-preview-2.2.6.tgz",
-      "integrity": "sha512-lS+wQ49jd/XyXu8tTWWZ38qfNJrAlxsDjkUrQoldfM1MdS6s18DxFV4dwP9xoAsq86kuSb/raXU8qJrH5dtV5w==",
-      "dependencies": {
-        "dompurify": "^2.0.8"
-      },
-      "peerDependencies": {
-        "prop-types": "^15",
-        "react": "^16 || ^17",
-        "react-dom": "^16 || ^17"
-      }
-    },
     "node_modules/react-overlays": {
       "version": "5.2.0",
       "resolved": "https://registry.npmjs.org/react-overlays/-/react-overlays-5.2.0.tgz",
@@ -43849,14 +43835,6 @@
       "integrity": "sha512-j1U1CWWs68nBPOg7tkQqnlFcAMFF6oEK6MgqAo15f8A5p7mjH6xyKn2gHbkcimpwfO0VQXqxAswnSYVr8lWzjw==",
       "requires": {}
     },
-    "react-mathjax-preview": {
-      "version": "2.2.6",
-      "resolved": "https://registry.npmjs.org/react-mathjax-preview/-/react-mathjax-preview-2.2.6.tgz",
-      "integrity": "sha512-lS+wQ49jd/XyXu8tTWWZ38qfNJrAlxsDjkUrQoldfM1MdS6s18DxFV4dwP9xoAsq86kuSb/raXU8qJrH5dtV5w==",
-      "requires": {
-        "dompurify": "^2.0.8"
-      }
-    },
     "react-overlays": {
       "version": "5.2.0",
       "resolved": "https://registry.npmjs.org/react-overlays/-/react-overlays-5.2.0.tgz",

public/index.html

@@ -9,7 +9,7 @@
       href="<%=htmlWebpackPlugin.options.FAVICON_URL%>"
       type="image/x-icon"
     />
-    <script>
+    <script defer>
       window.MathJax = {
         tex: {
           inlineMath: [
@@ -180,7 +180,6 @@
           var r = (window.lightningjs = t(e));
           (r.require = t), (r.modules = n);
         })({});
-
     </script>
     <!-- end usabilla live embed code -->
   </body>

src/components/FormikErrorFeedback.jsx

@@ -5,31 +5,26 @@ import { getIn, useFormikContext } from 'formik';
 
 import { Form, TransitionReplace } from '@edx/paragon';
 
-function FormikErrorFeedback({ name }) {
+const FormikErrorFeedback = ({ name }) => {
-  const {
+  const { touched, errors } = useFormikContext();
-    touched,
-    errors,
-  } = useFormikContext();
   const fieldTouched = getIn(touched, name);
   const fieldError = getIn(errors, name);
 
   return (
     <TransitionReplace>
-      {fieldTouched && fieldError
+      {fieldTouched && fieldError ? (
-        ? (
+        <Form.Control.Feedback type="invalid" hasIcon={false} key={`${name}-error-feedback`}>
-          <Form.Control.Feedback type="invalid" hasIcon={false} key={`${name}-error-feedback`}>
+          {fieldError}
-            {fieldError}
+        </Form.Control.Feedback>
-          </Form.Control.Feedback>
+      ) : (
-        )
+        <React.Fragment key={`${name}-no-error-feedback`} />
-        : (
+      )}
-          <React.Fragment key={`${name}-no-error-feedback`} />
-        )}
     </TransitionReplace>
   );
-}
+};
 
 FormikErrorFeedback.propTypes = {
   name: PropTypes.string.isRequired,
 };
 
-export default FormikErrorFeedback;
+export default React.memo(FormikErrorFeedback);

src/components/HTMLLoader.jsx

@@ -12,9 +12,9 @@ const defaultSanitizeOptions = {
   ADD_ATTR: ['columnalign'],
 };
 
-function HTMLLoader({
+const HTMLLoader = ({
   htmlNode, componentId, cssClassName, testId, delay,
-}) {
+}) => {
   const sanitizedMath = DOMPurify.sanitize(htmlNode, { ...defaultSanitizeOptions });
   const previewRef = useRef(null);
   const debouncedPostContent = useDebounce(htmlNode, delay);
@@ -45,7 +45,7 @@ function HTMLLoader({
   return (
     <div ref={previewRef} className={cssClassName} id={componentId} data-testid={testId} />
   );
-}
+};
 
 HTMLLoader.propTypes = {
   htmlNode: PropTypes.node,
@@ -63,4 +63,4 @@ HTMLLoader.defaultProps = {
   delay: 0,
 };
 
-export default HTMLLoader;
+export default React.memo(HTMLLoader);

src/components/NavigationBar/CourseTabsNavigation.jsx

@@ -4,7 +4,7 @@ import PropTypes from 'prop-types';
 import classNames from 'classnames';
 import { useDispatch, useSelector } from 'react-redux';
 
-import { injectIntl, intlShape } from '@edx/frontend-platform/i18n';
+import { useIntl } from '@edx/frontend-platform/i18n';
 
 import { fetchTab } from './data/thunks';
 import Tabs from './tabs/Tabs';
@@ -12,12 +12,13 @@ import messages from './messages';
 
 import './navBar.scss';
 
-function CourseTabsNavigation({
+const CourseTabsNavigation = ({
-  activeTab, className, intl, courseId, rootSlug,
+  activeTab, className, courseId, rootSlug,
-}) {
+}) => {
   const dispatch = useDispatch();
-
+  const intl = useIntl();
   const tabs = useSelector(state => state.courseTabs.tabs);
+
   useEffect(() => {
     dispatch(fetchTab(courseId, rootSlug));
   }, [courseId]);
@@ -25,8 +26,7 @@ function CourseTabsNavigation({
   return (
     <div id="courseTabsNavigation" className={classNames('course-tabs-navigation', className)}>
       <div className="container-xl">
-        {!!tabs.length
+        {!!tabs.length && (
-          && (
           <Tabs
             className="nav-underline-tabs"
             aria-label={intl.formatMessage(messages.courseMaterial)}
@@ -41,18 +41,17 @@ function CourseTabsNavigation({
               </a>
             ))}
           </Tabs>
-          )}
+        )}
       </div>
     </div>
   );
-}
+};
 
 CourseTabsNavigation.propTypes = {
   activeTab: PropTypes.string,
   className: PropTypes.string,
   rootSlug: PropTypes.string,
   courseId: PropTypes.string.isRequired,
-  intl: intlShape.isRequired,
 };
 
 CourseTabsNavigation.defaultProps = {
@@ -61,4 +60,4 @@ CourseTabsNavigation.defaultProps = {
   rootSlug: 'outline',
 };
 
-export default injectIntl(CourseTabsNavigation);
+export default React.memo(CourseTabsNavigation);

src/components/PostPreviewPanel.jsx

@@ -1,16 +1,17 @@
 import React, { useState } from 'react';
 import PropTypes from 'prop-types';
 
-import { injectIntl, intlShape } from '@edx/frontend-platform/i18n';
+import { useIntl } from '@edx/frontend-platform/i18n';
 import { Button, Icon, IconButton } from '@edx/paragon';
 import { Close } from '@edx/paragon/icons';
 
 import messages from '../discussions/posts/post-editor/messages';
 import HTMLLoader from './HTMLLoader';
 
-function PostPreviewPanel({
+const PostPreviewPanel = ({
-  htmlNode, intl, isPost, editExisting,
+  htmlNode, isPost, editExisting,
-}) {
+}) => {
+  const intl = useIntl();
   const [showPreviewPane, setShowPreviewPane] = useState(false);
 
   return (
@@ -30,13 +31,15 @@ function PostPreviewPanel({
             iconClassNames="icon-size"
             data-testid="hide-preview-button"
           />
-          <HTMLLoader
+          {htmlNode && (
-            htmlNode={htmlNode}
+            <HTMLLoader
-            cssClassName="text-primary"
+              htmlNode={htmlNode}
-            componentId="post-preview"
+              cssClassName="text-primary"
-            testId="post-preview"
+              componentId="post-preview"
-            delay={500}
+              testId="post-preview"
-          />
+              delay={500}
+            />
+          )}
         </div>
       )}
       <div className="d-flex justify-content-end">
@@ -55,18 +58,18 @@ function PostPreviewPanel({
       </div>
     </>
   );
-}
+};
 
 PostPreviewPanel.propTypes = {
-  intl: intlShape.isRequired,
+  htmlNode: PropTypes.node,
-  htmlNode: PropTypes.node.isRequired,
   isPost: PropTypes.bool,
   editExisting: PropTypes.bool,
 };
 
 PostPreviewPanel.defaultProps = {
+  htmlNode: '',
   isPost: false,
   editExisting: false,
 };
 
-export default injectIntl(PostPreviewPanel);
+export default React.memo(PostPreviewPanel);

src/components/Search.jsx

@@ -1,9 +1,11 @@
-import React, { useContext, useEffect } from 'react';
+import React, {
+  useCallback, useContext, useEffect, useState,
+} from 'react';
 
 import camelCase from 'lodash/camelCase';
 import { useDispatch, useSelector } from 'react-redux';
 
-import { injectIntl, intlShape } from '@edx/frontend-platform/i18n';
+import { useIntl } from '@edx/frontend-platform/i18n';
 import { Icon, SearchField } from '@edx/paragon';
 import { Search as SearchIcon } from '@edx/paragon/icons';
 
@@ -13,7 +15,8 @@ import { setSearchQuery } from '../discussions/posts/data';
 import postsMessages from '../discussions/posts/post-actions-bar/messages';
 import { setFilter as setTopicFilter } from '../discussions/topics/data/slices';
 
-function Search({ intl }) {
+const Search = () => {
+  const intl = useIntl();
   const dispatch = useDispatch();
   const { page } = useContext(DiscussionContext);
   const postSearch = useSelector(({ threads }) => threads.filters.search);
@@ -21,8 +24,9 @@ function Search({ intl }) {
   const learnerSearch = useSelector(({ learners }) => learners.usernameSearch);
   const isPostSearch = ['posts', 'my-posts'].includes(page);
   const isTopicSearch = 'topics'.includes(page);
-  let searchValue = '';
+  const [searchValue, setSearchValue] = useState('');
   let currentValue = '';
+
   if (isPostSearch) {
     currentValue = postSearch;
   } else if (isTopicSearch) {
@@ -31,20 +35,21 @@ function Search({ intl }) {
     currentValue = learnerSearch;
   }
 
-  const onClear = () => {
+  const onClear = useCallback(() => {
     dispatch(setSearchQuery(''));
     dispatch(setTopicFilter(''));
     dispatch(setUsernameSearch(''));
-  };
+  }, []);
 
-  const onChange = (query) => {
+  const onChange = useCallback((query) => {
-    searchValue = query;
+    setSearchValue(query);
-  };
+  }, []);
 
-  const onSubmit = (query) => {
+  const onSubmit = useCallback((query) => {
     if (query === '') {
       return;
     }
+
     if (isPostSearch) {
       dispatch(setSearchQuery(query));
     } else if (page === 'topics') {
@@ -52,36 +57,36 @@ function Search({ intl }) {
     } else if (page === 'learners') {
       dispatch(setUsernameSearch(query));
     }
-  };
+  }, [page, searchValue]);
+
+  const handleIconClick = useCallback((e) => {
+    e.preventDefault();
+    onSubmit(searchValue);
+  }, [searchValue]);
 
   useEffect(() => onClear(), [page]);
-  return (
-    <>
-      <SearchField.Advanced
-        onClear={onClear}
-        onChange={onChange}
-        onSubmit={onSubmit}
-        value={currentValue}
-      >
-        <SearchField.Label />
-        <SearchField.Input
-          style={{ paddingRight: '1rem' }}
-          placeholder={intl.formatMessage(postsMessages.search, { page: camelCase(page) })}
-        />
-        <span className="mt-auto mb-auto mr-2.5 pointer-cursor-hover">
-          <Icon
-            src={SearchIcon}
-            onClick={() => onSubmit(searchValue)}
-            data-testid="search-icon"
-          />
-        </span>
-      </SearchField.Advanced>
-    </>
-  );
-}
 
-Search.propTypes = {
+  return (
-  intl: intlShape.isRequired,
+    <SearchField.Advanced
+      onClear={onClear}
+      onChange={onChange}
+      onSubmit={onSubmit}
+      value={currentValue}
+    >
+      <SearchField.Label />
+      <SearchField.Input
+        style={{ paddingRight: '1rem' }}
+        placeholder={intl.formatMessage(postsMessages.search, { page: camelCase(page) })}
+      />
+      <span className="py-auto px-2.5 pointer-cursor-hover">
+        <Icon
+          src={SearchIcon}
+          onClick={handleIconClick}
+          data-testid="search-icon"
+        />
+      </span>
+    </SearchField.Advanced>
+  );
 };
 
-export default injectIntl(Search);
+export default React.memo(Search);

src/components/SearchInfo.jsx

@@ -1,32 +1,36 @@
 import React from 'react';
 import PropTypes from 'prop-types';
 
-import { injectIntl, intlShape } from '@edx/frontend-platform/i18n';
+import { useIntl } from '@edx/frontend-platform/i18n';
 import { Button, Icon } from '@edx/paragon';
 import { Search } from '@edx/paragon/icons';
 
 import { RequestStatus } from '../data/constants';
 import messages from '../discussions/posts/post-actions-bar/messages';
 
-function SearchInfo({
+const SearchInfo = ({
-  intl,
   count,
   text,
   loadingStatus,
   onClear,
   textSearchRewrite,
-}) {
+}) => {
+  const intl = useIntl();
+
   return (
     <div className="d-flex flex-row border-bottom border-light-400">
       <Icon src={Search} className="justify-content-start ml-3.5 mr-2 mb-2 mt-2.5" />
       <Button variant="" size="inline" className="text-justify p-2">
         {loadingStatus === RequestStatus.SUCCESSFUL && (
-          textSearchRewrite ? intl.formatMessage(messages.searchRewriteInfo, {
+          textSearchRewrite ? (
-            searchString: text,
+            intl.formatMessage(messages.searchRewriteInfo, {
-            count,
+              searchString: text,
-            textSearchRewrite,
+              count,
-          })
+              textSearchRewrite,
-            : intl.formatMessage(messages.searchInfo, { count, text })
+            })
+          ) : (
+            intl.formatMessage(messages.searchInfo, { count, text })
+          )
         )}
         {loadingStatus !== RequestStatus.SUCCESSFUL && intl.formatMessage(messages.searchInfoSearching)}
       </Button>
@@ -35,10 +39,9 @@ function SearchInfo({
       </Button>
     </div>
   );
-}
+};
 
 SearchInfo.propTypes = {
-  intl: intlShape.isRequired,
   count: PropTypes.number.isRequired,
   text: PropTypes.string.isRequired,
   loadingStatus: PropTypes.string.isRequired,
@@ -51,4 +54,4 @@ SearchInfo.defaultProps = {
   textSearchRewrite: null,
 };
 
-export default injectIntl(SearchInfo);
+export default React.memo(SearchInfo);

src/components/Spinner.jsx

@@ -0,0 +1,11 @@
+import React from 'react';
+
+import { Spinner as ParagonSpinner } from '@edx/paragon';
+
+const Spinner = () => (
+  <div className="spinner-container">
+    <ParagonSpinner animation="border" variant="primary" size="lg" />
+  </div>
+);
+
+export default React.memo(Spinner);

src/components/TinyMCEEditor.jsx

@@ -1,4 +1,4 @@
-import React, { useState } from 'react';
+import React, { useCallback, useState } from 'react';
 
 import { Editor } from '@tinymce/tinymce-react';
 import { useParams } from 'react-router';
@@ -42,30 +42,31 @@ import contentCss from '!!raw-loader!tinymce/skins/content/default/content.min.c
 import contentUiCss from '!!raw-loader!tinymce/skins/ui/oxide/content.min.css';
 
 /* istanbul ignore next */
-const setup = (editor) => {
+function TinyMCEEditor(props) {
-  editor.ui.registry.addButton('openedx_code', {
-    icon: 'sourcecode',
-    onAction: () => {
-      editor.execCommand('CodeSample');
-    },
-  });
-  editor.ui.registry.addButton('openedx_html', {
-    text: 'HTML',
-    onAction: () => {
-      editor.execCommand('mceCodeEditor');
-    },
-  });
-};
-
-/* istanbul ignore next */
-export default function TinyMCEEditor(props) {
   // note that skin and content_css is disabled to avoid the normal
   // loading process and is instead loaded as a string via content_style
 
   const { courseId, postId } = useParams();
   const [showImageWarning, setShowImageWarning] = useState(false);
   const intl = useIntl();
-  const uploadHandler = async (blobInfo, success, failure) => {
+
+  /* istanbul ignore next */
+  const setup = useCallback((editor) => {
+    editor.ui.registry.addButton('openedx_code', {
+      icon: 'sourcecode',
+      onAction: () => {
+        editor.execCommand('CodeSample');
+      },
+    });
+    editor.ui.registry.addButton('openedx_html', {
+      text: 'HTML',
+      onAction: () => {
+        editor.execCommand('mceCodeEditor');
+      },
+    });
+  }, []);
+
+  const uploadHandler = useCallback(async (blobInfo, success, failure) => {
     try {
       const blob = blobInfo.blob();
       const imageSize = blobInfo.blob().size / 1024;
@@ -76,7 +77,7 @@ export default function TinyMCEEditor(props) {
       const filename = blobInfo.filename();
       const { location } = await uploadFile(blob, filename, courseId, postId || 'root');
       const img = new Image();
-      img.onload = function () {
+      img.onload = () => {
         if (img.height > 999 || img.width > 999) { setShowImageWarning(true); }
       };
       img.src = location;
@@ -84,7 +85,11 @@ export default function TinyMCEEditor(props) {
     } catch (e) {
       failure(e.toString(), { remove: true });
     }
-  };
+  }, [courseId, postId]);
+
+  const handleClose = useCallback(() => {
+    setShowImageWarning(false);
+  }, []);
 
   let contentStyle;
   // In the test environment this causes an error so set styles to empty since they aren't needed for testing.
@@ -131,21 +136,22 @@ export default function TinyMCEEditor(props) {
       <AlertModal
         title={intl.formatMessage(messages.imageWarningModalTitle)}
         isOpen={showImageWarning}
-        onClose={() => setShowImageWarning(false)}
+        onClose={handleClose}
         isBlocking
         footerNode={(
           <ActionRow>
-            <Button variant="danger" onClick={() => setShowImageWarning(false)}>
+            <Button variant="danger" onClick={handleClose}>
               {intl.formatMessage(messages.imageWarningDismissButton)}
             </Button>
           </ActionRow>
-                )}
+        )}
       >
         <p>
           {intl.formatMessage(messages.imageWarningMessage)}
         </p>
       </AlertModal>
     </>
-
   );
 }
+
+export default React.memo(TinyMCEEditor);

src/components/TopicStats.jsx

@@ -4,7 +4,7 @@ import PropTypes from 'prop-types';
 
 import { useSelector } from 'react-redux';
 
-import { injectIntl, intlShape } from '@edx/frontend-platform/i18n';
+import { useIntl } from '@edx/frontend-platform/i18n';
 import { Icon, OverlayTrigger, Tooltip } from '@edx/paragon';
 import { HelpOutline, PostOutline, Report } from '@edx/paragon/icons';
 
@@ -14,15 +14,16 @@ import {
 } from '../discussions/data/selectors';
 import messages from '../discussions/in-context-topics/messages';
 
-function TopicStats({
+const TopicStats = ({
   threadCounts,
   activeFlags,
   inactiveFlags,
-  intl,
+}) => {
-}) {
+  const intl = useIntl();
   const userHasModerationPrivileges = useSelector(selectUserHasModerationPrivileges);
   const userIsGroupTa = useSelector(selectUserIsGroupTa);
   const canSeeReportedStats = (activeFlags || inactiveFlags) && (userHasModerationPrivileges || userIsGroupTa);
+
   return (
     <div className="d-flex align-items-center mt-2.5" style={{ marginBottom: '2px' }}>
       <OverlayTrigger
@@ -87,7 +88,7 @@ function TopicStats({
       )}
     </div>
   );
-}
+};
 
 TopicStats.propTypes = {
   threadCounts: PropTypes.shape({
@@ -96,7 +97,6 @@ TopicStats.propTypes = {
   }),
   activeFlags: PropTypes.number,
   inactiveFlags: PropTypes.number,
-  intl: intlShape.isRequired,
 };
 
 TopicStats.defaultProps = {
@@ -108,4 +108,4 @@ TopicStats.defaultProps = {
   inactiveFlags: null,
 };
 
-export default injectIntl(TopicStats);
+export default React.memo(TopicStats);

src/components/index.js

@@ -1,4 +1,5 @@
 export { default as PostActionsBar } from '../discussions/posts/post-actions-bar/PostActionsBar';
 export { default as Search } from './Search';
+export { default as Spinner } from './Spinner';
 export { default as TinyMCEEditor } from './TinyMCEEditor';
 export { default as TopicStats } from './TopicStats';

src/data/hooks.js

@@ -18,11 +18,13 @@ import { useDispatch } from 'react-redux';
 export function useDispatchWithState() {
   const dispatch = useDispatch();
   const [isDispatching, setDispatching] = useState(false);
+
   const dispatchWithState = async (thunk) => {
     setDispatching(true);
     await dispatch(thunk);
     setDispatching(false);
   };
+
   return [
     isDispatching,
     dispatchWithState,

src/discussions/common/ActionsDropdown.jsx

@@ -1,9 +1,11 @@
-import React, { useCallback, useRef, useState } from 'react';
+import React, {
+  useCallback, useMemo, useRef, useState,
+} from 'react';
 import PropTypes from 'prop-types';
 
 import { useSelector } from 'react-redux';
 
-import { injectIntl, intlShape } from '@edx/frontend-platform/i18n';
+import { useIntl } from '@edx/frontend-platform/i18n';
 import { logError } from '@edx/frontend-platform/logging';
 import {
   Button, Dropdown, Icon, IconButton, ModalPopup, useToggle,
@@ -13,22 +15,22 @@ import { MoreHoriz } from '@edx/paragon/icons';
 import { ContentActions } from '../../data/constants';
 import { selectBlackoutDate } from '../data/selectors';
 import messages from '../messages';
-import { commentShape } from '../post-comments/comments/comment/proptypes';
-import { postShape } from '../posts/post/proptypes';
 import { inBlackoutDateRange, useActions } from '../utils';
 
 function ActionsDropdown({
-  intl,
-  commentOrPost,
-  disabled,
   actionHandlers,
-  iconSize,
+  contentType,
+  disabled,
   dropDownIconSize,
+  iconSize,
+  id,
 }) {
   const buttonRef = useRef();
+  const intl = useIntl();
   const [isOpen, open, close] = useToggle(false);
   const [target, setTarget] = useState(null);
-  const actions = useActions(commentOrPost);
+  const blackoutDateRange = useSelector(selectBlackoutDate);
+  const actions = useActions(contentType, id);
 
   const handleActions = useCallback((action) => {
     const actionFunction = actionHandlers[action];
@@ -39,11 +41,12 @@ function ActionsDropdown({
     }
   }, [actionHandlers]);
 
-  const blackoutDateRange = useSelector(selectBlackoutDate);
   // Find and remove edit action if in blackout date range.
-  if (inBlackoutDateRange(blackoutDateRange)) {
+  useMemo(() => {
-    actions.splice(actions.findIndex(action => action.id === 'edit'), 1);
+    if (inBlackoutDateRange(blackoutDateRange)) {
-  }
+      actions.splice(actions.findIndex(action => action.id === 'edit'), 1);
+    }
+  }, [actions, blackoutDateRange]);
 
   const onClickButton = useCallback(() => {
     setTarget(buttonRef.current);
@@ -80,9 +83,7 @@ function ActionsDropdown({
           >
             {actions.map(action => (
               <React.Fragment key={action.id}>
-                {(action.action === ContentActions.DELETE)
+                {(action.action === ContentActions.DELETE) && <Dropdown.Divider />}
-                  && <Dropdown.Divider />}
-
                 <Dropdown.Item
                   as={Button}
                   variant="tertiary"
@@ -111,12 +112,12 @@ function ActionsDropdown({
 }
 
 ActionsDropdown.propTypes = {
-  intl: intlShape.isRequired,
+  id: PropTypes.string.isRequired,
-  commentOrPost: PropTypes.oneOfType([commentShape, postShape]).isRequired,
   disabled: PropTypes.bool,
   actionHandlers: PropTypes.objectOf(PropTypes.func).isRequired,
   iconSize: PropTypes.string,
   dropDownIconSize: PropTypes.bool,
+  contentType: PropTypes.oneOf(['POST', 'COMMENT']).isRequired,
 };
 
 ActionsDropdown.defaultProps = {
@@ -125,4 +126,4 @@ ActionsDropdown.defaultProps = {
   dropDownIconSize: false,
 };
 
-export default injectIntl(ActionsDropdown);
+export default ActionsDropdown;

src/discussions/common/AlertBanner.jsx

@@ -4,7 +4,7 @@ import PropTypes from 'prop-types';
 import { useSelector } from 'react-redux';
 
 import { getAuthenticatedUser } from '@edx/frontend-platform/auth';
-import { injectIntl, intlShape } from '@edx/frontend-platform/i18n';
+import { useIntl } from '@edx/frontend-platform/i18n';
 import { Alert } from '@edx/paragon';
 import { Report } from '@edx/paragon/icons';
 
@@ -12,26 +12,31 @@ import { AvatarOutlineAndLabelColors } from '../../data/constants';
 import {
   selectModerationSettings, selectUserHasModerationPrivileges, selectUserIsGroupTa, selectUserIsStaff,
 } from '../data/selectors';
-import { commentShape } from '../post-comments/comments/comment/proptypes';
 import messages from '../post-comments/messages';
-import { postShape } from '../posts/post/proptypes';
 import AlertBar from './AlertBar';
 
-function AlertBanner({
+const AlertBanner = ({
-  intl,
+  author,
-  content,
+  abuseFlagged,
-}) {
+  lastEdit,
+  closed,
+  closedBy,
+  closeReason,
+  editByLabel,
+  closedByLabel,
+}) => {
+  const intl = useIntl();
   const userHasModerationPrivileges = useSelector(selectUserHasModerationPrivileges);
   const userIsGroupTa = useSelector(selectUserIsGroupTa);
   const userIsGlobalStaff = useSelector(selectUserIsStaff);
   const { reasonCodesEnabled } = useSelector(selectModerationSettings);
-  const userIsContentAuthor = getAuthenticatedUser().username === content.author;
+  const userIsContentAuthor = getAuthenticatedUser().username === author;
-  const canSeeReportedBanner = content?.abuseFlagged;
+  const canSeeReportedBanner = abuseFlagged;
   const canSeeLastEditOrClosedAlert = (userHasModerationPrivileges || userIsGroupTa
     || userIsGlobalStaff || userIsContentAuthor
   );
-  const editByLabelColor = AvatarOutlineAndLabelColors[content.editByLabel];
+  const editByLabelColor = AvatarOutlineAndLabelColors[editByLabel];
-  const closedByLabelColor = AvatarOutlineAndLabelColors[content.closedByLabel];
+  const closedByLabelColor = AvatarOutlineAndLabelColors[closedByLabel];
 
   return (
     <>
@@ -42,33 +47,52 @@ function AlertBanner({
       )}
       {reasonCodesEnabled && canSeeLastEditOrClosedAlert && (
         <>
-          {content.lastEdit?.reason && (
+          {lastEdit?.reason && (
             <AlertBar
-              message={messages.editedBy}
+              message={intl.formatMessage(messages.editedBy)}
-              author={content.lastEdit.editorUsername}
+              author={lastEdit.editorUsername}
-              authorLabel={content.editByLabel}
+              authorLabel={editByLabel}
               labelColor={editByLabelColor && `text-${editByLabelColor}`}
-              reason={content.lastEdit.reason}
+              reason={lastEdit.reason}
             />
           )}
-          {content.closed && (
+          {closed && (
-          <AlertBar
+            <AlertBar
-            message={messages.closedBy}
+              message={intl.formatMessage(messages.closedBy)}
-            author={content.closedBy}
+              author={closedBy}
-            authorLabel={content.closedByLabel}
+              authorLabel={closedByLabel}
-            labelColor={closedByLabelColor && `text-${closedByLabelColor}`}
+              labelColor={closedByLabelColor && `text-${closedByLabelColor}`}
-            reason={content.closeReason}
+              reason={closeReason}
-          />
+            />
           )}
         </>
       )}
     </>
   );
-}
-
-AlertBanner.propTypes = {
-  intl: intlShape.isRequired,
-  content: PropTypes.oneOfType([commentShape.isRequired, postShape.isRequired]).isRequired,
 };
 
-export default injectIntl(AlertBanner);
+AlertBanner.propTypes = {
+  author: PropTypes.string.isRequired,
+  abuseFlagged: PropTypes.bool,
+  closed: PropTypes.bool,
+  closedBy: PropTypes.string,
+  closedByLabel: PropTypes.string,
+  closeReason: PropTypes.string,
+  editByLabel: PropTypes.string,
+  lastEdit: PropTypes.shape({
+    editorUsername: PropTypes.string,
+    reason: PropTypes.string,
+  }),
+};
+
+AlertBanner.defaultProps = {
+  abuseFlagged: false,
+  closed: undefined,
+  closedBy: undefined,
+  closedByLabel: undefined,
+  closeReason: undefined,
+  editByLabel: undefined,
+  lastEdit: {},
+};
+
+export default React.memo(AlertBanner);

src/discussions/common/AlertBar.jsx

@@ -1,24 +1,25 @@
 import React from 'react';
 import PropTypes from 'prop-types';
 
-import { injectIntl, intlShape } from '@edx/frontend-platform/i18n';
+import { useIntl } from '@edx/frontend-platform/i18n';
 import { Alert } from '@edx/paragon';
 
 import messages from '../post-comments/messages';
 import AuthorLabel from './AuthorLabel';
 
-function AlertBar({
+const AlertBar = ({
-  intl,
   message,
   author,
   authorLabel,
   labelColor,
   reason,
-}) {
+}) => {
+  const intl = useIntl();
+
   return (
     <Alert variant="info" className="px-3 shadow-none mb-1 py-10px bg-light-200">
       <div className="d-flex align-items-center flex-wrap text-gray-700 font-style">
-        {intl.formatMessage(message)}
+        {message}
         <span className="ml-1">
           <AuthorLabel
             author={author}
@@ -38,10 +39,9 @@ function AlertBar({
       </div>
     </Alert>
   );
-}
+};
 
 AlertBar.propTypes = {
-  intl: intlShape.isRequired,
   message: PropTypes.string,
   author: PropTypes.string,
   authorLabel: PropTypes.string,
@@ -57,4 +57,4 @@ AlertBar.defaultProps = {
   reason: '',
 };
 
-export default injectIntl(AlertBar);
+export default React.memo(AlertBar);

src/discussions/common/AuthorLabel.jsx

@@ -1,23 +1,22 @@
-import React, { useContext } from 'react';
+import React, { useContext, useMemo } from 'react';
 import PropTypes from 'prop-types';
 
 import classNames from 'classnames';
-import { Link, useLocation } from 'react-router-dom';
+import { generatePath } from 'react-router';
+import { Link } from 'react-router-dom';
 import * as timeago from 'timeago.js';
 
-import { injectIntl, intlShape } from '@edx/frontend-platform/i18n';
+import { useIntl } from '@edx/frontend-platform/i18n';
 import { Icon, OverlayTrigger, Tooltip } from '@edx/paragon';
 import { Institution, School } from '@edx/paragon/icons';
 
 import { Routes } from '../../data/constants';
 import { useShowLearnersTab } from '../data/hooks';
 import messages from '../messages';
-import { discussionsPath } from '../utils';
 import { DiscussionContext } from './context';
 import timeLocale from './time-locale';
 
-function AuthorLabel({
+const AuthorLabel = ({
-  intl,
   author,
   authorLabel,
   linkToProfile,
@@ -26,17 +25,18 @@ function AuthorLabel({
   postCreatedAt,
   authorToolTip,
   postOrComment,
-}) {
+}) => {
-  const location = useLocation();
+  timeago.register('time-locale', timeLocale);
+  const intl = useIntl();
   const { courseId } = useContext(DiscussionContext);
   let icon = null;
   let authorLabelMessage = null;
-  timeago.register('time-locale', timeLocale);
 
   if (authorLabel === 'Staff') {
     icon = Institution;
     authorLabelMessage = intl.formatMessage(messages.authorLabelStaff);
   }
+
   if (authorLabel === 'Community TA') {
     icon = School;
     authorLabelMessage = intl.formatMessage(messages.authorLabelTA);
@@ -49,7 +49,7 @@ function AuthorLabel({
   const showUserNameAsLink = useShowLearnersTab()
     && linkToProfile && author && author !== intl.formatMessage(messages.anonymous);
 
-  const authorName = (
+  const authorName = useMemo(() => (
     <span
       className={classNames('mr-1.5 font-size-14 font-style font-weight-500', {
         'text-gray-700': isRetiredUser,
@@ -60,8 +60,9 @@ function AuthorLabel({
     >
       {isRetiredUser ? '[Deactivated]' : author}
     </span>
-  );
+  ), [author, authorLabelMessage, isRetiredUser]);
-  const labelContents = (
+
+  const labelContents = useMemo(() => (
     <>
       <OverlayTrigger
         overlay={(
@@ -109,7 +110,7 @@ function AuthorLabel({
         </span>
       )}
     </>
-  );
+  ), [author, authorLabelMessage, authorToolTip, icon, isRetiredUser, postCreatedAt, showTextPrimary, alert]);
 
   return showUserNameAsLink
     ? (
@@ -117,7 +118,7 @@ function AuthorLabel({
         <Link
           data-testid="learner-posts-link"
           id="learner-posts-link"
-          to={discussionsPath(Routes.LEARNERS.POSTS, { learnerUsername: author, courseId })(location)}
+          to={generatePath(Routes.LEARNERS.POSTS, { learnerUsername: author, courseId })}
           className="text-decoration-none"
           style={{ width: 'fit-content' }}
         >
@@ -127,10 +128,9 @@ function AuthorLabel({
       </div>
     )
     : <div className={className}>{authorName}{labelContents}</div>;
-}
+};
 
 AuthorLabel.propTypes = {
-  intl: intlShape.isRequired,
   author: PropTypes.string.isRequired,
   authorLabel: PropTypes.string,
   linkToProfile: PropTypes.bool,
@@ -151,4 +151,4 @@ AuthorLabel.defaultProps = {
   postOrComment: false,
 };
 
-export default injectIntl(AuthorLabel);
+export default React.memo(AuthorLabel);

src/discussions/common/Confirmation.jsx

@@ -1,13 +1,12 @@
 import React from 'react';
 import PropTypes from 'prop-types';
 
-import { injectIntl, intlShape } from '@edx/frontend-platform/i18n';
+import { useIntl } from '@edx/frontend-platform/i18n';
 import { ActionRow, Button, ModalDialog } from '@edx/paragon';
 
 import messages from '../messages';
 
 function Confirmation({
-  intl,
   isOpen,
   title,
   description,
@@ -17,6 +16,8 @@ function Confirmation({
   confirmButtonVariant,
   confirmButtonText,
 }) {
+  const intl = useIntl();
+
   return (
     <ModalDialog title={title} isOpen={isOpen} hasCloseButton={false} onClose={onClose} zIndex={5000}>
       <ModalDialog.Header>
@@ -42,7 +43,6 @@ function Confirmation({
 }
 
 Confirmation.propTypes = {
-  intl: intlShape.isRequired,
   isOpen: PropTypes.bool.isRequired,
   onClose: PropTypes.func.isRequired,
   comfirmAction: PropTypes.func.isRequired,
@@ -59,4 +59,4 @@ Confirmation.defaultProps = {
   confirmButtonText: '',
 };
 
-export default injectIntl(Confirmation);
+export default React.memo(Confirmation);

src/discussions/common/EndorsedAlertBanner.jsx

@@ -1,30 +1,34 @@
-import React from 'react';
+import React, { useContext } from 'react';
 import PropTypes from 'prop-types';
 
 import * as timeago from 'timeago.js';
 
-import { injectIntl, intlShape } from '@edx/frontend-platform/i18n';
+import { useIntl } from '@edx/frontend-platform/i18n';
 import { Alert, Icon } from '@edx/paragon';
 import { CheckCircle, Verified } from '@edx/paragon/icons';
 
 import { ThreadType } from '../../data/constants';
-import { commentShape } from '../post-comments/comments/comment/proptypes';
 import messages from '../post-comments/messages';
+import { PostCommentsContext } from '../post-comments/postCommentsContext';
 import AuthorLabel from './AuthorLabel';
 import timeLocale from './time-locale';
 
 function EndorsedAlertBanner({
-  intl,
+  endorsed,
-  content,
+  endorsedAt,
-  postType,
+  endorsedBy,
+  endorsedByLabel,
 }) {
   timeago.register('time-locale', timeLocale);
+
+  const intl = useIntl();
+  const { postType } = useContext(PostCommentsContext);
   const isQuestion = postType === ThreadType.QUESTION;
   const classes = isQuestion ? 'bg-success-500 text-white' : 'bg-dark-500 text-white';
   const iconClass = isQuestion ? CheckCircle : Verified;
 
   return (
-    content.endorsed && (
+    endorsed && (
       <Alert
         variant="plain"
         className={`px-2.5 mb-0 py-8px align-items-center shadow-none ${classes}`}
@@ -45,11 +49,11 @@ function EndorsedAlertBanner({
           </div>
           <span className="d-flex align-items-center align-items-center flex-wrap" style={{ marginRight: '-1px' }}>
             <AuthorLabel
-              author={content.endorsedBy}
+              author={endorsedBy}
-              authorLabel={content.endorsedByLabel}
+              authorLabel={endorsedByLabel}
               linkToProfile
-              alert={content.endorsed}
+              alert={endorsed}
-              postCreatedAt={content.endorsedAt}
+              postCreatedAt={endorsedAt}
               authorToolTip
               postOrComment
             />
@@ -61,13 +65,16 @@ function EndorsedAlertBanner({
 }
 
 EndorsedAlertBanner.propTypes = {
-  intl: intlShape.isRequired,
+  endorsed: PropTypes.bool.isRequired,
-  content: PropTypes.oneOfType([commentShape.isRequired]).isRequired,
+  endorsedAt: PropTypes.string,
-  postType: PropTypes.string,
+  endorsedBy: PropTypes.string,
+  endorsedByLabel: PropTypes.string,
 };
 
 EndorsedAlertBanner.defaultProps = {
-  postType: null,
+  endorsedAt: null,
+  endorsedBy: null,
+  endorsedByLabel: null,
 };
 
-export default injectIntl(EndorsedAlertBanner);
+export default React.memo(EndorsedAlertBanner);

src/discussions/common/HoverCard.jsx

@@ -3,7 +3,7 @@ import PropTypes from 'prop-types';
 
 import classNames from 'classnames';
 
-import { injectIntl, intlShape } from '@edx/frontend-platform/i18n';
+import { useIntl } from '@edx/frontend-platform/i18n';
 import {
   Button, Icon, IconButton, OverlayTrigger, Tooltip,
 } from '@edx/paragon';
@@ -12,29 +12,32 @@ import {
   StarFilled, StarOutline, ThumbUpFilled, ThumbUpOutline,
 } from '../../components/icons';
 import { useUserCanAddThreadInBlackoutDate } from '../data/hooks';
-import { commentShape } from '../post-comments/comments/comment/proptypes';
+import { PostCommentsContext } from '../post-comments/postCommentsContext';
-import { postShape } from '../posts/post/proptypes';
 import ActionsDropdown from './ActionsDropdown';
 import { DiscussionContext } from './context';
 
-function HoverCard({
+const HoverCard = ({
-  intl,
+  id,
-  commentOrPost,
+  contentType,
   actionHandlers,
   handleResponseCommentButton,
   addResponseCommentButtonMessage,
   onLike,
   onFollow,
-  isClosedPost,
+  voted,
+  following,
   endorseIcons,
-}) {
+}) => {
+  const intl = useIntl();
   const { enableInContextSidebar } = useContext(DiscussionContext);
+  const { isClosed } = useContext(PostCommentsContext);
   const userCanAddThreadInBlackoutDate = useUserCanAddThreadInBlackoutDate();
+
   return (
     <div
       className="flex-fill justify-content-end align-items-center hover-card mr-n4 position-absolute"
-      data-testid={`hover-card-${commentOrPost.id}`}
+      data-testid={`hover-card-${id}`}
-      id={`hover-card-${commentOrPost.id}`}
+      id={`hover-card-${id}`}
     >
       {userCanAddThreadInBlackoutDate && (
         <div className="d-flex">
@@ -43,7 +46,7 @@ function HoverCard({
             className={classNames('px-2.5 py-2 border-0 font-style text-gray-700 font-size-12',
               { 'w-100': enableInContextSidebar })}
             onClick={() => handleResponseCommentButton()}
-            disabled={isClosedPost}
+            disabled={isClosed}
             style={{ lineHeight: '20px' }}
           >
             {addResponseCommentButtonMessage}
@@ -76,7 +79,7 @@ function HoverCard({
       )}
       <div className="hover-button">
         <IconButton
-          src={commentOrPost.voted ? ThumbUpFilled : ThumbUpOutline}
+          src={voted ? ThumbUpFilled : ThumbUpOutline}
           iconAs={Icon}
           size="sm"
           alt="Like"
@@ -87,10 +90,10 @@ function HoverCard({
           }}
         />
       </div>
-      {commentOrPost.following !== undefined && (
+      {following !== undefined && (
         <div className="hover-button">
           <IconButton
-            src={commentOrPost.following ? StarFilled : StarOutline}
+            src={following ? StarFilled : StarOutline}
             iconAs={Icon}
             size="sm"
             alt="Follow"
@@ -103,27 +106,34 @@ function HoverCard({
         </div>
       )}
       <div className="hover-button ml-auto">
-        <ActionsDropdown commentOrPost={commentOrPost} actionHandlers={actionHandlers} dropDownIconSize />
+        <ActionsDropdown
+          id={id}
+          contentType={contentType}
+          actionHandlers={actionHandlers}
+          dropDownIconSize
+        />
       </div>
     </div>
   );
-}
+};
 
 HoverCard.propTypes = {
-  intl: intlShape.isRequired,
+  id: PropTypes.string.isRequired,
-  commentOrPost: PropTypes.oneOfType([commentShape, postShape]).isRequired,
+  contentType: PropTypes.string.isRequired,
   actionHandlers: PropTypes.objectOf(PropTypes.func).isRequired,
   handleResponseCommentButton: PropTypes.func.isRequired,
-  onLike: PropTypes.func.isRequired,
-  onFollow: PropTypes.func,
   addResponseCommentButtonMessage: PropTypes.string.isRequired,
-  isClosedPost: PropTypes.bool.isRequired,
+  onLike: PropTypes.func.isRequired,
+  voted: PropTypes.bool.isRequired,
   endorseIcons: PropTypes.objectOf(PropTypes.any),
+  onFollow: PropTypes.func,
+  following: PropTypes.bool,
 };
 
 HoverCard.defaultProps = {
   onFollow: () => null,
   endorseIcons: null,
+  following: undefined,
 };
 
-export default injectIntl(HoverCard);
+export default React.memo(HoverCard);

src/discussions/data/constants.js

@@ -0,0 +1,12 @@
+import { selectCommentOrResponseById } from '../post-comments/data/selectors';
+import { selectThread } from '../posts/data/selectors';
+
+export const ContentSelectors = {
+  POST: selectThread,
+  COMMENT: selectCommentOrResponseById,
+};
+
+export const ContentTypes = {
+  POST: 'POST',
+  COMMENT: 'COMMENT',
+};

src/discussions/data/hooks.js

@@ -1,15 +1,13 @@
-/* eslint-disable import/prefer-default-export */
 import {
-  useContext,
+  useCallback,
-  useEffect,
+  useContext, useEffect, useMemo, useRef, useState,
-  useRef,
-  useState,
 } from 'react';
 
 import { useDispatch, useSelector } from 'react-redux';
 import { useHistory, useLocation, useRouteMatch } from 'react-router';
 
 import { getAuthenticatedUser } from '@edx/frontend-platform/auth';
+import { useIntl } from '@edx/frontend-platform/i18n';
 import { AppContext } from '@edx/frontend-platform/react';
 import { breakpoints, useWindowSize } from '@edx/paragon';
 
@@ -42,16 +40,14 @@ import { fetchCourseConfig } from './thunks';
 
 export function useTotalTopicThreadCount() {
   const topics = useSelector(selectTopics);
-
+  const count = useMemo(() => (
-  if (!topics) {
+    Object.keys(topics)?.reduce((total, topicId) => {
-    return 0;
-  }
-
-  return Object.keys(topics)
-    .reduce((total, topicId) => {
       const topic = topics[topicId];
       return total + topic.threadCounts.discussion + topic.threadCounts.question;
-    }, 0);
+    }, 0)),
+  []);
+
+  return count;
 }
 
 export const useSidebarVisible = () => {
@@ -87,13 +83,14 @@ export function useCourseDiscussionData(courseId) {
 
 export function useRedirectToThread(courseId, enableInContextSidebar) {
   const dispatch = useDispatch();
-  const redirectToThread = useSelector(
-    (state) => state.threads.redirectToThread,
-  );
   const history = useHistory();
   const location = useLocation();
 
-  return useEffect(() => {
+  const redirectToThread = useSelector(
+    (state) => state.threads.redirectToThread,
+  );
+
+  useEffect(() => {
     // After posting a new thread we'd like to redirect users to it, the topic and post id are temporarily
     // stored in redirectToThread
     if (redirectToThread) {
@@ -153,17 +150,20 @@ export function useContainerSize(refContainer) {
   return height;
 }
 
-export const useAlertBannerVisible = (content) => {
+export const useAlertBannerVisible = (
+  {
+    author, abuseFlagged, lastEdit, closed,
+  } = {},
+) => {
   const userHasModerationPrivileges = useSelector(selectUserHasModerationPrivileges);
   const userIsGroupTa = useSelector(selectUserIsGroupTa);
   const { reasonCodesEnabled } = useSelector(selectModerationSettings);
-  const userIsContentAuthor = getAuthenticatedUser().username === content.author;
+  const userIsContentAuthor = getAuthenticatedUser().username === author;
   const canSeeLastEditOrClosedAlert = (userHasModerationPrivileges || userIsContentAuthor || userIsGroupTa);
-  const canSeeReportedBanner = content.abuseFlagged;
+  const canSeeReportedBanner = abuseFlagged;
 
   return (
-    (reasonCodesEnabled && canSeeLastEditOrClosedAlert && (content.lastEdit?.reason || content.closed))
+    (reasonCodesEnabled && canSeeLastEditOrClosedAlert && (lastEdit?.reason || closed)) || (canSeeReportedBanner)
-    || (content.abuseFlagged && canSeeReportedBanner)
   );
 };
 
@@ -193,38 +193,50 @@ export const useCurrentDiscussionTopic = () => {
 export const useUserCanAddThreadInBlackoutDate = () => {
   const blackoutDateRange = useSelector(selectBlackoutDate);
   const isUserAdmin = useSelector(selectUserIsStaff);
-  const userHasModerationPrivilages = useSelector(selectUserHasModerationPrivileges);
+  const userHasModerationPrivileges = useSelector(selectUserHasModerationPrivileges);
   const isUserGroupTA = useSelector(selectUserIsGroupTa);
   const isCourseAdmin = useSelector(selectIsCourseAdmin);
   const isCourseStaff = useSelector(selectIsCourseStaff);
-  const isInBlackoutDateRange = inBlackoutDateRange(blackoutDateRange);
+  const isPrivileged = isUserAdmin || userHasModerationPrivileges || isUserGroupTA || isCourseAdmin || isCourseStaff;
+  const isInBlackoutDateRange = useMemo(() => inBlackoutDateRange(blackoutDateRange), [blackoutDateRange]);
 
-  return (!(isInBlackoutDateRange)
+  return (!(isInBlackoutDateRange) || (isPrivileged));
-    || (isUserAdmin || userHasModerationPrivilages || isUserGroupTA || isCourseAdmin || isCourseStaff));
 };
 
 function camelToConstant(string) {
   return string.replace(/[A-Z]/g, (match) => `_${match}`).toUpperCase();
 }
 
-export const useTourConfiguration = (intl) => {
+export const useTourConfiguration = () => {
+  const intl = useIntl();
   const dispatch = useDispatch();
-
   const { enableInContextSidebar } = useContext(DiscussionContext);
   const tours = useSelector(selectTours);
 
-  return tours.map((tour) => (
+  const handleOnDismiss = useCallback((id) => (
-    {
+    dispatch(updateTourShowStatus(id))
-      tourId: tour.tourName,
+  ), []);
-      advanceButtonText: intl.formatMessage(messages.advanceButtonText),
+
-      dismissButtonText: intl.formatMessage(messages.dismissButtonText),
+  const handleOnEnd = useCallback((id) => (
-      endButtonText: intl.formatMessage(messages.endButtonText),
+    dispatch(updateTourShowStatus(id))
-      enabled: tour && Boolean(tour.enabled && tour.showTour && !enableInContextSidebar),
+  ), []);
-      onDismiss: () => dispatch(updateTourShowStatus(tour.id)),
+
-      onEnd: () => dispatch(updateTourShowStatus(tour.id)),
+  const toursConfig = useMemo(() => (
-      checkpoints: tourCheckpoints(intl)[camelToConstant(tour.tourName)],
+    tours?.map((tour) => (
-    }
+      {
-  ));
+        tourId: tour.tourName,
+        advanceButtonText: intl.formatMessage(messages.advanceButtonText),
+        dismissButtonText: intl.formatMessage(messages.dismissButtonText),
+        endButtonText: intl.formatMessage(messages.endButtonText),
+        enabled: tour && Boolean(tour.enabled && tour.showTour && !enableInContextSidebar),
+        onDismiss: () => handleOnDismiss(tour.id),
+        onEnd: () => handleOnEnd(tour.id),
+        checkpoints: tourCheckpoints(intl)[camelToConstant(tour.tourName)],
+      }
+    ))
+  ), [tours, enableInContextSidebar]);
+
+  return toursConfig;
 };
 
 export const useDebounce = (value, delay) => {

src/discussions/discussions-home/BlackoutInformationBanner.jsx

@@ -1,36 +1,39 @@
-import React, { useState } from 'react';
+import React, { useCallback, useMemo, useState } from 'react';
 
 import { useSelector } from 'react-redux';
 
-import { injectIntl, intlShape } from '@edx/frontend-platform/i18n';
+import { useIntl } from '@edx/frontend-platform/i18n';
 import { PageBanner } from '@edx/paragon';
 
 import { selectBlackoutDate } from '../data/selectors';
 import messages from '../messages';
 import { inBlackoutDateRange } from '../utils';
 
-function BlackoutInformationBanner({
+const BlackoutInformationBanner = () => {
-  intl,
+  const intl = useIntl();
-}) {
+  const blackoutDate = useSelector(selectBlackoutDate);
-  const isDiscussionsBlackout = inBlackoutDateRange(useSelector(selectBlackoutDate));
   const [showBanner, setShowBanner] = useState(true);
 
+  const isDiscussionsBlackout = useMemo(() => (
+    inBlackoutDateRange(blackoutDate)
+  ), [blackoutDate]);
+
+  const handleDismiss = useCallback(() => {
+    setShowBanner(false);
+  }, []);
+
   return (
     <PageBanner
       variant="accentB"
       show={isDiscussionsBlackout && showBanner}
       dismissible
-      onDismiss={() => setShowBanner(false)}
+      onDismiss={handleDismiss}
     >
       <div className="font-weight-500">
         {intl.formatMessage(messages.blackoutDiscussionInformation)}
       </div>
     </PageBanner>
   );
-}
-
-BlackoutInformationBanner.propTypes = {
-  intl: intlShape.isRequired,
 };
 
-export default injectIntl(BlackoutInformationBanner);
+export default BlackoutInformationBanner;

src/discussions/discussions-home/DiscussionContent.jsx

@@ -1,37 +1,39 @@
-import React from 'react';
+import React, { lazy, Suspense } from 'react';
 
 import { useSelector } from 'react-redux';
 import { Route, Switch } from 'react-router';
 
-import { injectIntl } from '@edx/frontend-platform/i18n';
+import Spinner from '../../components/Spinner';
-
 import { Routes } from '../../data/constants';
-import { PostCommentsView } from '../post-comments';
-import { PostEditor } from '../posts';
 
-function DiscussionContent() {
+const PostEditor = lazy(() => import('../posts/post-editor/PostEditor'));
+const PostCommentsView = lazy(() => import('../post-comments/PostCommentsView'));
+
+const DiscussionContent = () => {
   const postEditorVisible = useSelector((state) => state.threads.postEditorVisible);
 
   return (
     <div className="d-flex bg-light-400 flex-column w-75 w-xs-100 w-xl-75 align-items-center">
       <div className="d-flex flex-column w-100">
-        {postEditorVisible ? (
+        <Suspense fallback={(<Spinner />)}>
-          <Route path={Routes.POSTS.NEW_POST}>
+          {postEditorVisible ? (
-            <PostEditor />
+            <Route path={Routes.POSTS.NEW_POST}>
-          </Route>
+              <PostEditor />
-        ) : (
-          <Switch>
-            <Route path={Routes.POSTS.EDIT_POST}>
-              <PostEditor editExisting />
             </Route>
-            <Route path={Routes.COMMENTS.PATH}>
+          ) : (
-              <PostCommentsView />
+            <Switch>
-            </Route>
+              <Route path={Routes.POSTS.EDIT_POST}>
-          </Switch>
+                <PostEditor editExisting />
-        )}
+              </Route>
+              <Route path={Routes.COMMENTS.PATH}>
+                <PostCommentsView />
+              </Route>
+            </Switch>
+          )}
+        </Suspense>
       </div>
     </div>
   );
-}
+};
 
-export default injectIntl(DiscussionContent);
+export default DiscussionContent;

src/discussions/discussions-home/DiscussionSidebar.jsx

@@ -1,4 +1,6 @@
-import React, { useContext, useEffect, useRef } from 'react';
+import React, {
+  lazy, Suspense, useContext, useEffect, useRef,
+} from 'react';
 import PropTypes from 'prop-types';
 
 import classNames from 'classnames';
@@ -9,18 +11,22 @@ import {
 
 import { useWindowSize } from '@edx/paragon';
 
+import Spinner from '../../components/Spinner';
 import { RequestStatus, Routes } from '../../data/constants';
 import { DiscussionContext } from '../common/context';
 import {
   useContainerSize, useIsOnDesktop, useIsOnXLDesktop, useShowLearnersTab,
 } from '../data/hooks';
 import { selectconfigLoadingStatus, selectEnableInContext } from '../data/selectors';
-import { TopicPostsView, TopicsView as InContextTopicsView } from '../in-context-topics';
-import { LearnerPostsView, LearnersView } from '../learners';
-import { PostsView } from '../posts';
-import { TopicsView as LegacyTopicsView } from '../topics';
 
-export default function DiscussionSidebar({ displaySidebar, postActionBarRef }) {
+const TopicPostsView = lazy(() => import('../in-context-topics/TopicPostsView'));
+const InContextTopicsView = lazy(() => import('../in-context-topics/TopicsView'));
+const LearnerPostsView = lazy(() => import('../learners/LearnerPostsView'));
+const LearnersView = lazy(() => import('../learners/LearnersView'));
+const PostsView = lazy(() => import('../posts/PostsView'));
+const LegacyTopicsView = lazy(() => import('../topics/TopicsView'));
+
+const DiscussionSidebar = ({ displaySidebar, postActionBarRef }) => {
   const location = useLocation();
   const isOnDesktop = useIsOnDesktop();
   const isOnXLDesktop = useIsOnXLDesktop();
@@ -55,15 +61,16 @@ export default function DiscussionSidebar({ displaySidebar, postActionBarRef })
       })}
       data-testid="sidebar"
     >
-      <Switch>
+      <Suspense fallback={(<Spinner />)}>
-        {enableInContext && !enableInContextSidebar && (
+        <Switch>
+          {enableInContext && !enableInContextSidebar && (
           <Route
             path={Routes.TOPICS.ALL}
             component={InContextTopicsView}
             exact
           />
-        )}
+          )}
-        {enableInContext && !enableInContextSidebar && (
+          {enableInContext && !enableInContextSidebar && (
           <Route
             path={[
               Routes.TOPICS.TOPIC,
@@ -74,19 +81,19 @@ export default function DiscussionSidebar({ displaySidebar, postActionBarRef })
             component={TopicPostsView}
             exact
           />
-        )}
+          )}
-        <Route
+          <Route
-          path={[Routes.POSTS.ALL_POSTS, Routes.POSTS.MY_POSTS, Routes.POSTS.PATH, Routes.TOPICS.CATEGORY]}
+            path={[Routes.POSTS.ALL_POSTS, Routes.POSTS.MY_POSTS, Routes.POSTS.PATH, Routes.TOPICS.CATEGORY]}
-          component={PostsView}
+            component={PostsView}
-        />
+          />
-        <Route path={Routes.TOPICS.PATH} component={LegacyTopicsView} />
+          <Route path={Routes.TOPICS.PATH} component={LegacyTopicsView} />
-        {redirectToLearnersTab && (
+          {redirectToLearnersTab && (
           <Route path={Routes.LEARNERS.POSTS} component={LearnerPostsView} />
-        )}
+          )}
-        {redirectToLearnersTab && (
+          {redirectToLearnersTab && (
           <Route path={Routes.LEARNERS.PATH} component={LearnersView} />
-        )}
+          )}
-        {configStatus === RequestStatus.SUCCESSFUL && (
+          {configStatus === RequestStatus.SUCCESSFUL && (
           <Redirect
             from={Routes.DISCUSSIONS.PATH}
             to={{
@@ -94,15 +101,11 @@ export default function DiscussionSidebar({ displaySidebar, postActionBarRef })
               pathname: Routes.POSTS.ALL_POSTS,
             }}
           />
-        )}
+          )}
-      </Switch>
+        </Switch>
+      </Suspense>
     </div>
   );
-}
-
-DiscussionSidebar.defaultProps = {
-  displaySidebar: false,
-  postActionBarRef: null,
 };
 
 DiscussionSidebar.propTypes = {
@@ -112,3 +115,10 @@ DiscussionSidebar.propTypes = {
     PropTypes.shape({ current: PropTypes.instanceOf(Element) }),
   ]),
 };
+
+DiscussionSidebar.defaultProps = {
+  displaySidebar: false,
+  postActionBarRef: null,
+};
+
+export default React.memo(DiscussionSidebar);

src/discussions/discussions-home/DiscussionsHome.jsx

@@ -1,4 +1,4 @@
-import React, { useEffect, useRef } from 'react';
+import React, { lazy, Suspense, useRef } from 'react';
 
 import classNames from 'classnames';
 import { useSelector } from 'react-redux';
@@ -6,12 +6,10 @@ import {
   Route, Switch, useLocation, useRouteMatch,
 } from 'react-router';
 
-import Footer from '@edx/frontend-component-footer';
 import { LearningHeader as Header } from '@edx/frontend-component-header';
 import { getConfig } from '@edx/frontend-platform';
 
-import { PostActionsBar } from '../../components';
+import { Spinner } from '../../components';
-import { CourseTabsNavigation } from '../../components/NavigationBar';
 import { selectCourseTabs } from '../../components/NavigationBar/data/selectors';
 import { ALL_ROUTES, DiscussionProvider, Routes } from '../../data/constants';
 import { DiscussionContext } from '../common/context';
@@ -22,17 +20,21 @@ import { selectDiscussionProvider, selectEnableInContext } from '../data/selecto
 import { EmptyLearners, EmptyPosts, EmptyTopics } from '../empty-posts';
 import { EmptyTopic as InContextEmptyTopics } from '../in-context-topics/components';
 import messages from '../messages';
-import { LegacyBreadcrumbMenu, NavigationBar } from '../navigation';
 import { selectPostEditorVisible } from '../posts/data/selectors';
-import DiscussionsProductTour from '../tours/DiscussionsProductTour';
-import { postMessageToParent } from '../utils';
-import BlackoutInformationBanner from './BlackoutInformationBanner';
-import DiscussionContent from './DiscussionContent';
-import DiscussionSidebar from './DiscussionSidebar';
 import useFeedbackWrapper from './FeedbackWrapper';
-import InformationBanner from './InformationBanner';
 
-export default function DiscussionsHome() {
+const Footer = lazy(() => import('@edx/frontend-component-footer'));
+const PostActionsBar = lazy(() => import('../posts/post-actions-bar/PostActionsBar'));
+const CourseTabsNavigation = lazy(() => import('../../components/NavigationBar/CourseTabsNavigation'));
+const LegacyBreadcrumbMenu = lazy(() => import('../navigation/breadcrumb-menu/LegacyBreadcrumbMenu'));
+const NavigationBar = lazy(() => import('../navigation/navigation-bar/NavigationBar'));
+const DiscussionsProductTour = lazy(() => import('../tours/DiscussionsProductTour'));
+const BlackoutInformationBanner = lazy(() => import('./BlackoutInformationBanner'));
+const DiscussionContent = lazy(() => import('./DiscussionContent'));
+const DiscussionSidebar = lazy(() => import('./DiscussionSidebar'));
+const InformationBanner = lazy(() => import('./InformationBanner'));
+
+const DiscussionsHome = () => {
   const location = useLocation();
   const postActionBarRef = useRef(null);
   const postEditorVisible = useSelector(selectPostEditorVisible);
@@ -40,7 +42,6 @@ export default function DiscussionsHome() {
   const enableInContext = useSelector(selectEnableInContext);
   const { courseNumber, courseTitle, org } = useSelector(selectCourseTabs);
   const { params: { page } } = useRouteMatch(`${Routes.COMMENTS.PAGE}?`);
-  const { params: { path } } = useRouteMatch(`${Routes.DISCUSSIONS.PATH}/:path*`);
   const { params } = useRouteMatch(ALL_ROUTES);
   const isRedirectToLearners = useShowLearnersTab();
   const isOnDesktop = useIsOnDesktop();
@@ -60,54 +61,60 @@ export default function DiscussionsHome() {
   const displayContentArea = (postId || postEditorVisible || (learnerUsername && postId));
   if (displayContentArea) { displaySidebar = isOnDesktop; }
 
-  useEffect(() => {
-    if (path && path !== 'undefined') {
-      postMessageToParent('discussions.navigate', { path });
-    }
-  }, [path]);
-
   return (
-    <DiscussionContext.Provider value={{
+    <Suspense fallback={(<Spinner />)}>
-      page,
+      <DiscussionContext.Provider value={{
-      courseId,
+        page,
-      postId,
+        courseId,
-      topicId,
+        postId,
-      enableInContextSidebar,
+        topicId,
-      category,
+        enableInContextSidebar,
-      learnerUsername,
+        category,
-    }}
+        learnerUsername,
-    >
+      }}
-      {!enableInContextSidebar && <Header courseOrg={org} courseNumber={courseNumber} courseTitle={courseTitle} />}
+      >
-      <main className="container-fluid d-flex flex-column p-0 w-100" id="main" tabIndex="-1">
+        {!enableInContextSidebar && (
-        {!enableInContextSidebar && <CourseTabsNavigation activeTab="discussion" courseId={courseId} />}
+          <Header courseOrg={org} courseNumber={courseNumber} courseTitle={courseTitle} />
-        <div
-          className={classNames('header-action-bar', {
-            'shadow-none border-light-300 border-bottom': enableInContextSidebar,
-          })}
-          ref={postActionBarRef}
-        >
-          <div
-            className={classNames('d-flex flex-row justify-content-between navbar fixed-top', {
-              'pl-4 pr-3 py-0': enableInContextSidebar,
-            })}
-          >
-            {!enableInContextSidebar && <Route path={Routes.DISCUSSIONS.PATH} component={NavigationBar} />}
-            <PostActionsBar />
-          </div>
-          {isFeedbackBannerVisible && <InformationBanner />}
-          <BlackoutInformationBanner />
-        </div>
-        {provider === DiscussionProvider.LEGACY && (
-          <Route
-            path={[Routes.POSTS.PATH, Routes.TOPICS.CATEGORY]}
-            component={LegacyBreadcrumbMenu}
-          />
         )}
-
+        <main className="container-fluid d-flex flex-column p-0 w-100" id="main" tabIndex="-1">
-        <div className="d-flex flex-row">
+          {!enableInContextSidebar && <CourseTabsNavigation activeTab="discussion" courseId={courseId} />}
-          <DiscussionSidebar displaySidebar={displaySidebar} postActionBarRef={postActionBarRef} />
+          <div
-          {displayContentArea && <DiscussionContent />}
+            className={classNames('header-action-bar', {
-          {!displayContentArea && (
+              'shadow-none border-light-300 border-bottom': enableInContextSidebar,
+            })}
+            ref={postActionBarRef}
+          >
+            <div
+              className={classNames('d-flex flex-row justify-content-between navbar fixed-top', {
+                'pl-4 pr-3 py-0': enableInContextSidebar,
+              })}
+            >
+              {!enableInContextSidebar && (
+                <NavigationBar />
+              )}
+              <PostActionsBar />
+            </div>
+            {isFeedbackBannerVisible && <InformationBanner />}
+            <BlackoutInformationBanner />
+          </div>
+          {provider === DiscussionProvider.LEGACY && (
+          <Suspense fallback={(<Spinner />)}>
+            <Route
+              path={[Routes.POSTS.PATH, Routes.TOPICS.CATEGORY]}
+              component={LegacyBreadcrumbMenu}
+            />
+          </Suspense>
+          )}
+          <div className="d-flex flex-row position-relative">
+            <Suspense fallback={(<Spinner />)}>
+              <DiscussionSidebar displaySidebar={displaySidebar} postActionBarRef={postActionBarRef} />
+            </Suspense>
+            {displayContentArea && (
+              <Suspense fallback={(<Spinner />)}>
+                <DiscussionContent />
+              </Suspense>
+            )}
+            {!displayContentArea && (
             <Switch>
               <Route
                 path={Routes.TOPICS.PATH}
@@ -123,11 +130,16 @@ export default function DiscussionsHome() {
               />
               {isRedirectToLearners && <Route path={Routes.LEARNERS.PATH} component={EmptyLearners} />}
             </Switch>
+            )}
+          </div>
+          {!enableInContextSidebar && (
+            <DiscussionsProductTour />
           )}
-        </div>
+        </main>
-        {!enableInContextSidebar && <DiscussionsProductTour />}
+        {!enableInContextSidebar && <Footer />}
-      </main>
+      </DiscussionContext.Provider>
-      {!enableInContextSidebar && <Footer />}
+    </Suspense>
-    </DiscussionContext.Provider>
   );
-}
+};
+
+export default React.memo(DiscussionsHome);

src/discussions/discussions-home/InformationBanner.jsx

@@ -1,16 +1,15 @@
-import React, { useState } from 'react';
+import React, { useCallback, useState } from 'react';
 
 import { useSelector } from 'react-redux';
 
-import { injectIntl, intlShape } from '@edx/frontend-platform/i18n';
+import { useIntl } from '@edx/frontend-platform/i18n';
 import { Hyperlink, PageBanner } from '@edx/paragon';
 
 import { selectUserIsStaff, selectUserRoles } from '../data/selectors';
 import messages from '../messages';
 
-function InformationBanner({
+const InformationBanner = () => {
-  intl,
+  const intl = useIntl();
-}) {
   const [showBanner, setShowBanner] = useState(true);
   const userRoles = useSelector(selectUserRoles);
   const isAdmin = useSelector(selectUserIsStaff);
@@ -20,12 +19,16 @@ function InformationBanner({
   const hideLearnMoreButton = ((userRoles.includes('Student') && userRoles.length === 1) || !userRoles.length) && !isAdmin;
   const showStaffLink = isAdmin || userRoles.includes('Moderator') || userRoles.includes('Administrator');
 
+  const handleDismiss = useCallback(() => {
+    setShowBanner(false);
+  }, []);
+
   return (
     <PageBanner
       variant="light"
       show={showBanner}
       dismissible
-      onDismiss={() => setShowBanner(false)}
+      onDismiss={handleDismiss}
     >
       <div className="font-weight-500">
         {intl.formatMessage(messages.bannerMessage)}
@@ -55,10 +58,6 @@ function InformationBanner({
       </div>
     </PageBanner>
   );
-}
-
-InformationBanner.propTypes = {
-  intl: intlShape.isRequired,
 };
 
-export default injectIntl(InformationBanner);
+export default InformationBanner;

src/discussions/empty-posts/EmptyLearners.jsx

@@ -1,12 +1,13 @@
 import React from 'react';
 
-import { injectIntl, intlShape } from '@edx/frontend-platform/i18n';
+import { useIntl } from '@edx/frontend-platform/i18n';
 
 import { useIsOnDesktop } from '../data/hooks';
 import messages from '../messages';
 import EmptyPage from './EmptyPage';
 
-function EmptyLearners({ intl }) {
+const EmptyLearners = () => {
+  const intl = useIntl();
   const isOnDesktop = useIsOnDesktop();
 
   if (!isOnDesktop) {
@@ -16,10 +17,6 @@ function EmptyLearners({ intl }) {
   return (
     <EmptyPage title={intl.formatMessage(messages.emptyTitle)} />
   );
-}
-
-EmptyLearners.propTypes = {
-  intl: intlShape.isRequired,
 };
 
-export default injectIntl(EmptyLearners);
+export default EmptyLearners;

src/discussions/empty-posts/EmptyPage.jsx

@@ -7,13 +7,13 @@ import { Button } from '@edx/paragon';
 
 import { ReactComponent as EmptyIcon } from '../../assets/empty.svg';
 
-function EmptyPage({
+const EmptyPage = ({
   title,
   subTitle = null,
   action = null,
   actionText = null,
   fullWidth = false,
-}) {
+}) => {
   const containerClasses = classNames(
     'min-content-height justify-content-center align-items-center d-flex w-100 flex-column',
     { 'bg-light-400': !fullWidth },
@@ -33,7 +33,7 @@ function EmptyPage({
       </div>
     </div>
   );
-}
+};
 
 EmptyPage.propTypes = {
   title: propTypes.string.isRequired,
@@ -50,4 +50,4 @@ EmptyPage.defaultProps = {
   actionText: null,
 };
 
-export default EmptyPage;
+export default React.memo(EmptyPage);

src/discussions/empty-posts/EmptyPosts.jsx

@@ -1,9 +1,9 @@
-import React from 'react';
+import React, { useCallback } from 'react';
 import propTypes from 'prop-types';
 
 import { useDispatch, useSelector } from 'react-redux';
 
-import { injectIntl, intlShape } from '@edx/frontend-platform/i18n';
+import { useIntl } from '@edx/frontend-platform/i18n';
 
 import { useIsOnDesktop } from '../data/hooks';
 import { selectAreThreadsFiltered, selectPostThreadCount } from '../data/selectors';
@@ -11,16 +11,16 @@ import messages from '../messages';
 import { messages as postMessages, showPostEditor } from '../posts';
 import EmptyPage from './EmptyPage';
 
-function EmptyPosts({ intl, subTitleMessage }) {
+const EmptyPosts = ({ subTitleMessage }) => {
+  const intl = useIntl();
   const dispatch = useDispatch();
-
+  const isOnDesktop = useIsOnDesktop();
   const isFiltered = useSelector(selectAreThreadsFiltered);
   const totalThreads = useSelector(selectPostThreadCount);
-  const isOnDesktop = useIsOnDesktop();
 
-  function addPost() {
+  const addPost = useCallback(() => (
-    return dispatch(showPostEditor());
+    dispatch(showPostEditor())
-  }
+  ), []);
 
   let title = messages.noPostSelected;
   let subTitle = null;
@@ -49,7 +49,7 @@ function EmptyPosts({ intl, subTitleMessage }) {
       fullWidth={fullWidth}
     />
   );
-}
+};
 
 EmptyPosts.propTypes = {
   subTitleMessage: propTypes.shape({
@@ -57,7 +57,6 @@ EmptyPosts.propTypes = {
     defaultMessage: propTypes.string,
     description: propTypes.string,
   }).isRequired,
-  intl: intlShape.isRequired,
 };
 
-export default injectIntl(EmptyPosts);
+export default React.memo(EmptyPosts);

src/discussions/empty-posts/EmptyTopics.jsx

@@ -1,9 +1,9 @@
-import React from 'react';
+import React, { useCallback } from 'react';
 
 import { useDispatch, useSelector } from 'react-redux';
 import { useRouteMatch } from 'react-router';
 
-import { injectIntl, intlShape } from '@edx/frontend-platform/i18n';
+import { useIntl } from '@edx/frontend-platform/i18n';
 
 import { ALL_ROUTES } from '../../data/constants';
 import { useIsOnDesktop, useTotalTopicThreadCount } from '../data/hooks';
@@ -12,18 +12,17 @@ import messages from '../messages';
 import { messages as postMessages, showPostEditor } from '../posts';
 import EmptyPage from './EmptyPage';
 
-function EmptyTopics({ intl }) {
+const EmptyTopics = () => {
+  const intl = useIntl();
   const match = useRouteMatch(ALL_ROUTES);
   const dispatch = useDispatch();
-
+  const isOnDesktop = useIsOnDesktop();
   const hasGlobalThreads = useTotalTopicThreadCount() > 0;
   const topicThreadCount = useSelector(selectTopicThreadCount(match.params.topicId));
 
-  function addPost() {
+  const addPost = useCallback(() => (
-    return dispatch(showPostEditor());
+    dispatch(showPostEditor())
-  }
+  ), []);
-
-  const isOnDesktop = useIsOnDesktop();
 
   let title = messages.emptyTitle;
   let fullWidth = false;
@@ -62,10 +61,6 @@ function EmptyTopics({ intl }) {
       fullWidth={fullWidth}
     />
   );
-}
-
-EmptyTopics.propTypes = {
-  intl: intlShape.isRequired,
 };
 
-export default injectIntl(EmptyTopics);
+export default EmptyTopics;

src/discussions/in-context-topics/TopicPostsView.jsx

@@ -1,15 +1,17 @@
-import React, { useContext, useEffect } from 'react';
+import React, {
+  useCallback, useContext, useEffect, useMemo,
+} from 'react';
 
 import { useDispatch, useSelector } from 'react-redux';
 import { useLocation } from 'react-router-dom';
 
-import { injectIntl, intlShape } from '@edx/frontend-platform/i18n';
+import { useIntl } from '@edx/frontend-platform/i18n';
 import { Spinner } from '@edx/paragon';
 
 import { RequestStatus, Routes } from '../../data/constants';
 import { DiscussionContext } from '../common/context';
 import { selectDiscussionProvider } from '../data/selectors';
-import { selectTopicThreads } from '../posts/data/selectors';
+import { selectTopicThreadsIds } from '../posts/data/selectors';
 import PostsList from '../posts/PostsList';
 import { discussionsPath, handleKeyDown } from '../utils';
 import {
@@ -21,19 +23,34 @@ import { BackButton, NoResults } from './components';
 import messages from './messages';
 import { Topic } from './topic';
 
-function TopicPostsView({ intl }) {
+const TopicPostsView = () => {
+  const intl = useIntl();
   const location = useLocation();
   const dispatch = useDispatch();
   const { courseId, topicId, category } = useContext(DiscussionContext);
   const provider = useSelector(selectDiscussionProvider);
   const topicsStatus = useSelector(selectLoadingStatus);
-  const topicsInProgress = topicsStatus === RequestStatus.IN_PROGRESS;
+  const postsIds = useSelector(selectTopicThreadsIds([topicId]));
-  const posts = useSelector(selectTopicThreads([topicId]));
   const selectedSubsectionUnits = useSelector(selectSubsectionUnits(category));
   const selectedSubsection = useSelector(selectSubsection(category));
-  const selectedUnit = useSelector(selectUnits)?.find(unit => unit.id === topicId);
+  const units = useSelector(selectUnits);
-  const selectedNonCoursewareTopic = useSelector(selectNonCoursewareTopics)?.find(topic => topic.id === topicId);
+  const nonCoursewareTopics = useSelector(selectNonCoursewareTopics);
   const selectedArchivedTopic = useSelector(selectArchivedTopic(topicId));
+  const topicsInProgress = topicsStatus === RequestStatus.IN_PROGRESS;
+
+  const selectedUnit = useMemo(() => (
+    units?.find(unit => unit.id === topicId)
+  ), [units, topicId]);
+
+  const selectedNonCoursewareTopic = useMemo(() => (
+    nonCoursewareTopics?.find(topic => topic.id === topicId)
+  ), [nonCoursewareTopics, topicId]);
+
+  const backButtonPath = useCallback(() => {
+    const path = selectedUnit ? Routes.TOPICS.CATEGORY : Routes.TOPICS.ALL;
+    const params = selectedUnit ? { courseId, category: selectedUnit?.parentId } : { courseId };
+    return discussionsPath(path, params)(location);
+  }, [selectedUnit]);
 
   useEffect(() => {
     if (provider && topicsStatus === RequestStatus.IDLE) {
@@ -41,12 +58,6 @@ function TopicPostsView({ intl }) {
     }
   }, [provider]);
 
-  const backButtonPath = () => {
-    const path = selectedUnit ? Routes.TOPICS.CATEGORY : Routes.TOPICS.ALL;
-    const params = selectedUnit ? { courseId, category: selectedUnit?.parentId } : { courseId };
-    return discussionsPath(path, params)(location);
-  };
-
   return (
     <div className="discussion-posts d-flex flex-column h-100">
       {topicId ? (
@@ -67,8 +78,8 @@ function TopicPostsView({ intl }) {
       <div className="list-group list-group-flush flex-fill" role="list" onKeyDown={e => handleKeyDown(e)}>
         {topicId ? (
           <PostsList
-            posts={posts}
+            postsIds={postsIds}
-            topics={[topicId]}
+            topicsIds={[topicId]}
             parentIsLoading={topicsInProgress}
           />
         ) : (
@@ -90,10 +101,6 @@ function TopicPostsView({ intl }) {
       </div>
     </div>
   );
-}
-
-TopicPostsView.propTypes = {
-  intl: intlShape.isRequired,
 };
 
-export default injectIntl(TopicPostsView);
+export default React.memo(TopicPostsView);

src/discussions/in-context-topics/TopicsView.jsx

@@ -1,4 +1,6 @@
-import React, { useContext, useEffect } from 'react';
+import React, {
+  useCallback, useContext, useEffect, useMemo,
+} from 'react';
 
 import classNames from 'classnames';
 import isEmpty from 'lodash/isEmpty';
@@ -21,30 +23,38 @@ import { setFilter } from './data/slices';
 import { fetchCourseTopicsV3 } from './data/thunks';
 import { ArchivedBaseGroup, SectionBaseGroup, Topic } from './topic';
 
-function TopicsList() {
+const TopicsList = () => {
   const loadingStatus = useSelector(selectLoadingStatus);
   const coursewareTopics = useSelector(selectCoursewareTopics);
   const nonCoursewareTopics = useSelector(selectNonCoursewareTopics);
   const archivedTopics = useSelector(selectArchivedTopics);
 
+  const renderNonCoursewareTopics = useMemo(() => (
+    nonCoursewareTopics?.map((topic, index) => (
+      <Topic
+        key={topic.id}
+        topic={topic}
+        showDivider={(nonCoursewareTopics.length - 1) !== index}
+      />
+    ))
+  ), [nonCoursewareTopics]);
+
+  const renderCoursewareTopics = useMemo(() => (
+    coursewareTopics?.map((topic, index) => (
+      <SectionBaseGroup
+        key={topic.id}
+        section={topic?.children}
+        sectionId={topic.id}
+        sectionTitle={topic.displayName}
+        showDivider={(coursewareTopics.length - 1) !== index}
+      />
+    ))
+  ), [coursewareTopics]);
+
   return (
     <>
-      {nonCoursewareTopics?.map((topic, index) => (
+      {renderNonCoursewareTopics}
-        <Topic
+      {renderCoursewareTopics}
-          key={topic.id}
-          topic={topic}
-          showDivider={(nonCoursewareTopics.length - 1) !== index}
-        />
-      ))}
-      {coursewareTopics?.map((topic, index) => (
-        <SectionBaseGroup
-          key={topic.id}
-          section={topic?.children}
-          sectionId={topic.id}
-          sectionTitle={topic.displayName}
-          showDivider={(coursewareTopics.length - 1) !== index}
-        />
-      ))}
       {!isEmpty(archivedTopics) && (
         <ArchivedBaseGroup
           archivedTopics={archivedTopics}
@@ -58,9 +68,9 @@ function TopicsList() {
       )}
     </>
   );
-}
+};
 
-function TopicsView() {
+const TopicsView = () => {
   const dispatch = useDispatch();
   const { courseId } = useContext(DiscussionContext);
   const provider = useSelector(selectDiscussionProvider);
@@ -83,6 +93,10 @@ function TopicsView() {
     }
   }, [isPostsFiltered]);
 
+  const handleOnClear = useCallback(() => {
+    dispatch(setFilter(''));
+  }, []);
+
   return (
     <div className="d-flex flex-column h-100" data-testid="inContext-topics-view">
       {topicFilter && (
@@ -91,7 +105,7 @@ function TopicsView() {
             text={topicFilter}
             count={filteredTopics.length}
             loadingStatus={loadingStatus}
-            onClear={() => dispatch(setFilter(''))}
+            onClear={handleOnClear}
           />
           {filteredTopics.length === 0 && loadingStatus === RequestStatus.SUCCESSFUL && <NoResults />}
         </>
@@ -116,6 +130,6 @@ function TopicsView() {
       </div>
     </div>
   );
-}
+};
 
 export default TopicsView;

src/discussions/in-context-topics/components/EmptyTopics.jsx

@@ -1,9 +1,9 @@
-import React, { useContext } from 'react';
+import React, { useCallback, useContext } from 'react';
 
 import { useDispatch, useSelector } from 'react-redux';
 import { useRouteMatch } from 'react-router';
 
-import { injectIntl, intlShape } from '@edx/frontend-platform/i18n';
+import { useIntl } from '@edx/frontend-platform/i18n';
 
 import { ALL_ROUTES } from '../../../data/constants';
 import { DiscussionContext } from '../../common/context';
@@ -14,20 +14,20 @@ import messages from '../../messages';
 import { messages as postMessages, showPostEditor } from '../../posts';
 import { selectCourseWareThreadsCount, selectTotalTopicsThreadsCount } from '../data/selectors';
 
-function EmptyTopics({ intl }) {
+const EmptyTopics = () => {
+  const intl = useIntl();
   const match = useRouteMatch(ALL_ROUTES);
   const dispatch = useDispatch();
+  const isOnDesktop = useIsOnDesktop();
   const { enableInContextSidebar } = useContext(DiscussionContext);
   const courseWareThreadsCount = useSelector(selectCourseWareThreadsCount(match.params.category));
   const topicThreadsCount = useSelector(selectPostThreadCount);
   // hasGlobalThreads is used to determine if there are any post available in courseware and non-courseware topics
   const hasGlobalThreads = useSelector(selectTotalTopicsThreadsCount) > 0;
 
-  function addPost() {
+  const addPost = useCallback(() => (
-    return dispatch(showPostEditor());
+    dispatch(showPostEditor())
-  }
+  ), []);
-
-  const isOnDesktop = useIsOnDesktop();
 
   let title = messages.emptyTitle;
   let fullWidth = false;
@@ -74,10 +74,6 @@ function EmptyTopics({ intl }) {
       fullWidth={fullWidth}
     />
   );
-}
-
-EmptyTopics.propTypes = {
-  intl: intlShape.isRequired,
 };
 
-export default injectIntl(EmptyTopics);
+export default EmptyTopics;

src/discussions/in-context-topics/components/NoResults.jsx

@@ -1,11 +1,14 @@
+import React from 'react';
+
 import { useSelector } from 'react-redux';
 
-import { injectIntl, intlShape } from '@edx/frontend-platform/i18n';
+import { useIntl } from '@edx/frontend-platform/i18n';
 
 import { selectTopics } from '../data/selectors';
 import messages from '../messages';
 
-function NoResults({ intl }) {
+const NoResults = () => {
+  const intl = useIntl();
   const topics = useSelector(selectTopics);
 
   const title = messages.nothingHere;
@@ -20,10 +23,6 @@ function NoResults({ intl }) {
       { helpMessage && <small className="font-weight-normal text-gray-700">{intl.formatMessage(helpMessage)}</small>}
     </div>
   );
-}
-
-NoResults.propTypes = {
-  intl: intlShape.isRequired,
 };
 
-export default injectIntl(NoResults);
+export default NoResults;

src/discussions/in-context-topics/topic-search/TopicSearchBar.jsx

@@ -1,8 +1,8 @@
-import React, { useContext, useEffect } from 'react';
+import React, { useCallback, useContext, useEffect } from 'react';
 
 import { useDispatch, useSelector } from 'react-redux';
 
-import { injectIntl, intlShape } from '@edx/frontend-platform/i18n';
+import { useIntl } from '@edx/frontend-platform/i18n';
 import { Icon, SearchField } from '@edx/paragon';
 import { Search as SearchIcon } from '@edx/paragon/icons';
 
@@ -10,56 +10,51 @@ import { DiscussionContext } from '../../common/context';
 import postsMessages from '../../posts/post-actions-bar/messages';
 import { setFilter as setTopicFilter } from '../data/slices';
 
-function TopicSearchBar({ intl }) {
+const TopicSearchBar = () => {
+  const intl = useIntl();
   const dispatch = useDispatch();
   const { page } = useContext(DiscussionContext);
   const topicSearch = useSelector(({ inContextTopics }) => inContextTopics.filter);
   let searchValue = '';
 
-  const onClear = () => {
+  const onClear = useCallback(() => {
     dispatch(setTopicFilter(''));
-  };
+  }, []);
 
-  const onChange = (query) => {
+  const onChange = useCallback((query) => {
     searchValue = query;
-  };
+  }, []);
 
-  const onSubmit = (query) => {
+  const onSubmit = useCallback((query) => {
     if (query === '') {
       return;
     }
     dispatch(setTopicFilter(query));
-  };
+  }, []);
 
   useEffect(() => onClear(), [page]);
 
   return (
-    <>
+    <SearchField.Advanced
-      <SearchField.Advanced
+      onClear={onClear}
-        onClear={onClear}
+      onChange={onChange}
-        onChange={onChange}
+      onSubmit={onSubmit}
-        onSubmit={onSubmit}
+      value={topicSearch}
-        value={topicSearch}
+    >
-      >
+      <SearchField.Label />
-        <SearchField.Label />
+      <SearchField.Input
-        <SearchField.Input
+        style={{ paddingRight: '1rem' }}
-          style={{ paddingRight: '1rem' }}
+        placeholder={intl.formatMessage(postsMessages.search, { page: 'topics' })}
-          placeholder={intl.formatMessage(postsMessages.search, { page: 'topics' })}
+      />
+      <span className="mt-auto mb-auto mr-2.5 pointer-cursor-hover">
+        <Icon
+          src={SearchIcon}
+          onClick={() => onSubmit(searchValue)}
+          data-testid="search-icon"
         />
-        <span className="mt-auto mb-auto mr-2.5 pointer-cursor-hover">
+      </span>
-          <Icon
+    </SearchField.Advanced>
-            src={SearchIcon}
-            onClick={() => onSubmit(searchValue)}
-            data-testid="search-icon"
-          />
-        </span>
-      </SearchField.Advanced>
-    </>
   );
-}
-
-TopicSearchBar.propTypes = {
-  intl: intlShape.isRequired,
 };
 
-export default injectIntl(TopicSearchBar);
+export default TopicSearchBar;

src/discussions/in-context-topics/topic/ArchivedBaseGroup.jsx

@@ -1,16 +1,27 @@
-import React from 'react';
+import React, { useMemo } from 'react';
 import PropTypes from 'prop-types';
 
-import { injectIntl, intlShape } from '@edx/frontend-platform/i18n';
+import { useIntl } from '@edx/frontend-platform/i18n';
 
 import messages from '../messages';
 import Topic, { topicShape } from './Topic';
 
-function ArchivedBaseGroup({
+const ArchivedBaseGroup = ({
   archivedTopics,
   showDivider,
-  intl,
+}) => {
-}) {
+  const intl = useIntl();
+
+  const renderArchivedTopics = useMemo(() => (
+    archivedTopics?.map((topic, index) => (
+      <Topic
+        key={topic.id}
+        topic={topic}
+        showDivider={(archivedTopics.length - 1) !== index}
+      />
+    ))
+  ), [archivedTopics]);
+
   return (
     <>
       {showDivider && (
@@ -24,25 +35,18 @@ function ArchivedBaseGroup({
         data-testid="archived-group"
       >
         <div className="pt-3 px-4 font-weight-bold">{intl.formatMessage(messages.archivedTopics)}</div>
-        {archivedTopics?.map((topic, index) => (
+        {renderArchivedTopics}
-          <Topic
-            key={topic.id}
-            topic={topic}
-            showDivider={(archivedTopics.length - 1) !== index}
-          />
-        ))}
       </div>
     </>
   );
-}
+};
 
 ArchivedBaseGroup.propTypes = {
   archivedTopics: PropTypes.arrayOf(topicShape).isRequired,
   showDivider: PropTypes.bool,
-  intl: intlShape.isRequired,
 };
 
 ArchivedBaseGroup.defaultProps = {
   showDivider: false,
 };
-export default injectIntl(ArchivedBaseGroup);
+export default React.memo(ArchivedBaseGroup);

src/discussions/in-context-topics/topic/SectionBaseGroup.jsx

@@ -1,11 +1,11 @@
-import React from 'react';
+import React, { useCallback, useMemo } from 'react';
 import PropTypes from 'prop-types';
 
 import classNames from 'classnames';
 import { useParams } from 'react-router';
 import { Link } from 'react-router-dom';
 
-import { injectIntl, intlShape } from '@edx/frontend-platform/i18n';
+import { useIntl } from '@edx/frontend-platform/i18n';
 
 import TopicStats from '../../../components/TopicStats';
 import { Routes } from '../../../data/constants';
@@ -13,19 +13,52 @@ import { discussionsPath } from '../../utils';
 import messages from '../messages';
 import { topicShape } from './Topic';
 
-function SectionBaseGroup({
+const SectionBaseGroup = ({
   section,
   sectionTitle,
   sectionId,
   showDivider,
-  intl,
+}) => {
-}) {
+  const intl = useIntl();
   const { courseId } = useParams();
-  const isSelected = (id) => window.location.pathname.includes(id);
+
-  const sectionUrl = (id) => discussionsPath(Routes.TOPICS.CATEGORY, {
+  const isSelected = useCallback((id) => (
+    window.location.pathname.includes(id)
+  ), []);
+
+  const sectionUrl = useCallback((id) => discussionsPath(Routes.TOPICS.CATEGORY, {
     courseId,
     category: id,
-  });
+  }), [courseId]);
+
+  const renderSection = useMemo(() => (
+    section?.map((subsection, index) => (
+      <Link
+        className={classNames('subsection p-0 text-decoration-none text-primary-500', {
+          'border-bottom border-light-400': (section.length - 1 !== index),
+        })}
+        key={subsection.id}
+        role="option"
+        data-subsection-id={subsection.id}
+        data-testid="subsection-group"
+        to={sectionUrl(subsection.id)}
+        onClick={() => isSelected(subsection.id)}
+        aria-current={isSelected(section.id) ? 'page' : undefined}
+        tabIndex={(isSelected(subsection.id) || index === 0) ? 0 : -1}
+      >
+        <div className="d-flex flex-row pt-2.5 pb-2 px-4">
+          <div className="d-flex flex-column flex-fill" style={{ minWidth: 0 }}>
+            <div className="d-flex flex-column justify-content-start mw-100 flex-fill">
+              <div className="topic-name text-truncate">
+                {subsection?.displayName || intl.formatMessage(messages.unnamedSubsection)}
+              </div>
+              <TopicStats threadCounts={subsection?.threadCounts} />
+            </div>
+          </div>
+        </div>
+      </Link>
+    ))
+  ), [section, sectionUrl, isSelected]);
 
   return (
     <div
@@ -36,32 +69,7 @@ function SectionBaseGroup({
       <div className="pt-3 px-4 font-weight-bold">
         {sectionTitle || intl.formatMessage(messages.unnamedSection)}
       </div>
-      {section.map((subsection, index) => (
+      {renderSection}
-        <Link
-          className={classNames('subsection p-0 text-decoration-none text-primary-500', {
-            'border-bottom border-light-400': (section.length - 1 !== index),
-          })}
-          key={subsection.id}
-          role="option"
-          data-subsection-id={subsection.id}
-          data-testid="subsection-group"
-          to={sectionUrl(subsection.id)}
-          onClick={() => isSelected(subsection.id)}
-          aria-current={isSelected(section.id) ? 'page' : undefined}
-          tabIndex={(isSelected(subsection.id) || index === 0) ? 0 : -1}
-        >
-          <div className="d-flex flex-row pt-2.5 pb-2 px-4">
-            <div className="d-flex flex-column flex-fill" style={{ minWidth: 0 }}>
-              <div className="d-flex flex-column justify-content-start mw-100 flex-fill">
-                <div className="topic-name text-truncate">
-                  {subsection?.displayName || intl.formatMessage(messages.unnamedSubsection)}
-                </div>
-                <TopicStats threadCounts={subsection?.threadCounts} />
-              </div>
-            </div>
-          </div>
-        </Link>
-      ))}
       {showDivider && (
         <>
           <div className="divider border-top border-light-500" />
@@ -70,7 +78,7 @@ function SectionBaseGroup({
       )}
     </div>
   );
-}
+};
 
 SectionBaseGroup.propTypes = {
   section: PropTypes.arrayOf(PropTypes.shape({
@@ -86,7 +94,6 @@ SectionBaseGroup.propTypes = {
   sectionTitle: PropTypes.string.isRequired,
   sectionId: PropTypes.string.isRequired,
   showDivider: PropTypes.bool.isRequired,
-  intl: intlShape.isRequired,
 };
 
-export default injectIntl(SectionBaseGroup);
+export default React.memo(SectionBaseGroup);

src/discussions/in-context-topics/topic/Topic.jsx

@@ -7,7 +7,7 @@ import { useSelector } from 'react-redux';
 import { useParams } from 'react-router';
 import { Link } from 'react-router-dom';
 
-import { injectIntl, intlShape } from '@edx/frontend-platform/i18n';
+import { useIntl } from '@edx/frontend-platform/i18n';
 import { Icon, OverlayTrigger, Tooltip } from '@edx/paragon';
 import { HelpOutline, PostOutline, Report } from '@edx/paragon/icons';
 
@@ -17,12 +17,12 @@ import { selectUserHasModerationPrivileges, selectUserIsGroupTa } from '../../da
 import { discussionsPath } from '../../utils';
 import messages from '../messages';
 
-function Topic({
+const Topic = ({
   topic,
   showDivider,
   index,
-  intl,
+}) => {
-}) {
+  const intl = useIntl();
   const { courseId } = useParams();
   const userHasModerationPrivileges = useSelector(selectUserHasModerationPrivileges);
   const userIsGroupTa = useSelector(selectUserIsGroupTa);
@@ -70,7 +70,7 @@ function Topic({
       )}
     </>
   );
-}
+};
 
 export const topicShape = PropTypes.shape({
   id: PropTypes.string,
@@ -85,7 +85,6 @@ export const topicShape = PropTypes.shape({
 });
 
 Topic.propTypes = {
-  intl: intlShape.isRequired,
   topic: topicShape,
   showDivider: PropTypes.bool,
   index: PropTypes.number,
@@ -99,4 +98,4 @@ Topic.defaultProps = {
   },
 };
 
-export default injectIntl(Topic);
+export default React.memo(Topic);

src/discussions/learners/LearnerPostsView.jsx

@@ -6,7 +6,7 @@ import capitalize from 'lodash/capitalize';
 import { useDispatch, useSelector } from 'react-redux';
 import { useHistory, useLocation } from 'react-router-dom';
 
-import { injectIntl, intlShape } from '@edx/frontend-platform/i18n';
+import { useIntl } from '@edx/frontend-platform/i18n';
 import {
   Button, Icon, IconButton, Spinner,
 } from '@edx/paragon';
@@ -18,33 +18,36 @@ import {
 } from '../../data/constants';
 import { DiscussionContext } from '../common/context';
 import { selectUserHasModerationPrivileges, selectUserIsStaff } from '../data/selectors';
+import { usePostList } from '../posts/data/hooks';
 import {
-  selectAllThreads,
+  selectAllThreadsIds,
   selectThreadNextPage,
   threadsLoadingStatus,
 } from '../posts/data/selectors';
 import { clearPostsPages } from '../posts/data/slices';
 import NoResults from '../posts/NoResults';
 import { PostLink } from '../posts/post';
-import { discussionsPath, filterPosts } from '../utils';
+import { discussionsPath } from '../utils';
 import { fetchUserPosts } from './data/thunks';
 import LearnerPostFilterBar from './learner-post-filter-bar/LearnerPostFilterBar';
 import messages from './messages';
 
-function LearnerPostsView({ intl }) {
+const LearnerPostsView = () => {
+  const intl = useIntl();
   const location = useLocation();
   const history = useHistory();
   const dispatch = useDispatch();
 
-  const posts = useSelector(selectAllThreads);
+  const postsIds = useSelector(selectAllThreadsIds);
   const loadingStatus = useSelector(threadsLoadingStatus());
   const postFilter = useSelector(state => state.learners.postFilter);
   const { courseId, learnerUsername: username } = useContext(DiscussionContext);
   const nextPage = useSelector(selectThreadNextPage());
   const userHasModerationPrivileges = useSelector(selectUserHasModerationPrivileges);
   const userIsStaff = useSelector(selectUserIsStaff);
+  const sortedPostsIds = usePostList(postsIds);
 
-  const loadMorePosts = (pageNum = undefined) => {
+  const loadMorePosts = useCallback((pageNum = undefined) => {
     const params = {
       author: username,
       page: pageNum,
@@ -54,29 +57,24 @@ function LearnerPostsView({ intl }) {
     };
 
     dispatch(fetchUserPosts(courseId, params));
-  };
+  }, [courseId, postFilter, username, userHasModerationPrivileges, userIsStaff]);
+
+  const postInstances = useMemo(() => (
+    sortedPostsIds?.map((postId, idx) => (
+      <PostLink
+        postId={postId}
+        idx={idx}
+        key={postId}
+        showDivider={(sortedPostsIds.length - 1) !== idx}
+      />
+    ))
+  ), [sortedPostsIds]);
 
   useEffect(() => {
     dispatch(clearPostsPages());
     loadMorePosts();
   }, [courseId, postFilter, username]);
 
-  const checkIsSelected = (id) => window.location.pathname.includes(id);
-  const pinnedPosts = useMemo(() => filterPosts(posts, 'pinned'), [posts]);
-  const unpinnedPosts = useMemo(() => filterPosts(posts, 'unpinned'), [posts]);
-
-  const postInstances = useCallback((sortedPosts) => (
-    sortedPosts.map((post, idx) => (
-      <PostLink
-        post={post}
-        key={post.id}
-        isSelected={checkIsSelected}
-        idx={idx}
-        showDivider={(sortedPosts.length - 1) !== idx}
-      />
-    ))
-  ), []);
-
   return (
     <div className="discussion-posts d-flex flex-column">
       <div className="d-flex align-items-center justify-content-between px-2.5">
@@ -97,9 +95,8 @@ function LearnerPostsView({ intl }) {
       <LearnerPostFilterBar />
       <div className="border-bottom border-light-400" />
       <div className="list-group list-group-flush">
-        {postInstances(pinnedPosts)}
+        {postInstances}
-        {postInstances(unpinnedPosts)}
+        {loadingStatus !== RequestStatus.IN_PROGRESS && sortedPostsIds?.length === 0 && <NoResults />}
-        {loadingStatus !== RequestStatus.IN_PROGRESS && posts?.length === 0 && <NoResults />}
         {loadingStatus === RequestStatus.IN_PROGRESS ? (
           <div className="d-flex justify-content-center p-4">
             <Spinner animation="border" variant="primary" size="lg" />
@@ -114,10 +111,6 @@ function LearnerPostsView({ intl }) {
       </div>
     </div>
   );
-}
-
-LearnerPostsView.propTypes = {
-  intl: intlShape.isRequired,
 };
 
-export default injectIntl(LearnerPostsView);
+export default LearnerPostsView;

src/discussions/learners/LearnersView.jsx

@@ -1,11 +1,11 @@
-import React, { useEffect } from 'react';
+import React, { useCallback, useEffect, useMemo } from 'react';
 
 import { useDispatch, useSelector } from 'react-redux';
 import {
   Redirect, useLocation, useParams,
 } from 'react-router';
 
-import { injectIntl, intlShape } from '@edx/frontend-platform/i18n';
+import { useIntl } from '@edx/frontend-platform/i18n';
 import { Button, Spinner } from '@edx/paragon';
 
 import SearchInfo from '../../components/SearchInfo';
@@ -24,7 +24,8 @@ import { fetchLearners } from './data/thunks';
 import { LearnerCard, LearnerFilterBar } from './learner';
 import messages from './messages';
 
-function LearnersView({ intl }) {
+const LearnersView = () => {
+  const intl = useIntl();
   const { courseId } = useParams();
   const location = useLocation();
   const dispatch = useDispatch();
@@ -46,7 +47,7 @@ function LearnersView({ intl }) {
     }
   }, [courseId, orderBy, learnersTabEnabled, usernameSearch]);
 
-  const loadPage = async () => {
+  const loadPage = useCallback(async () => {
     if (nextPage) {
       dispatch(fetchLearners(courseId, {
         orderBy,
@@ -54,7 +55,19 @@ function LearnersView({ intl }) {
         usernameSearch,
       }));
     }
-  };
+  }, [courseId, orderBy, nextPage, usernameSearch]);
+
+  const handleOnClear = useCallback(() => {
+    dispatch(setUsernameSearch(''));
+  }, []);
+
+  const renderLearnersList = useMemo(() => (
+    (
+      courseConfigLoadingStatus === RequestStatus.SUCCESSFUL && learnersTabEnabled && learners.map((learner) => (
+        <LearnerCard learner={learner} key={learner.username} />
+      ))
+    ) || <></>
+  ), [courseConfigLoadingStatus, learnersTabEnabled, learners]);
 
   return (
     <div className="d-flex flex-column border-right border-light-400">
@@ -65,7 +78,7 @@ function LearnersView({ intl }) {
           text={usernameSearch}
           count={learners.length}
           loadingStatus={loadingStatus}
-          onClear={() => dispatch(setUsernameSearch(''))}
+          onClear={handleOnClear}
         />
       )}
       <div className="list-group list-group-flush learner" role="list">
@@ -77,12 +90,7 @@ function LearnersView({ intl }) {
           }}
         />
         )}
-        {courseConfigLoadingStatus === RequestStatus.SUCCESSFUL
+        {renderLearnersList}
-          && learnersTabEnabled
-          && learners.map((learner, index) => (
-            // eslint-disable-next-line react/no-array-index-key
-            <LearnerCard learner={learner} key={index} courseId={courseId} />
-          ))}
         {loadingStatus === RequestStatus.IN_PROGRESS ? (
           <div className="d-flex justify-content-center p-4">
             <Spinner animation="border" variant="primary" size="lg" />
@@ -98,10 +106,6 @@ function LearnersView({ intl }) {
       </div>
     </div>
   );
-}
-
-LearnersView.propTypes = {
-  intl: intlShape.isRequired,
 };
 
-export default injectIntl(LearnersView);
+export default LearnersView;

src/discussions/learners/learner/LearnerAvatar.jsx

@@ -1,26 +1,23 @@
 import React from 'react';
+import PropTypes from 'prop-types';
 
 import { Avatar } from '@edx/paragon';
 
-import { learnerShape } from './proptypes';
+const LearnerAvatar = ({ username }) => (
-
+  <div className="mr-3 mt-1">
-function LearnerAvatar({ learner }) {
+    <Avatar
-  return (
+      size="sm"
-    <div className="mr-3 mt-1">
+      alt={username}
-      <Avatar
+      style={{
-        size="sm"
+        height: '2rem',
-        alt={learner.username}
+        width: '2rem',
-        style={{
+      }}
-          height: '2rem',
+    />
-          width: '2rem',
+  </div>
-        }}
+);
-      />
-    </div>
-  );
-}
 
 LearnerAvatar.propTypes = {
-  learner: learnerShape.isRequired,
+  username: PropTypes.string.isRequired,
 };
 
-export default LearnerAvatar;
+export default React.memo(LearnerAvatar);

src/discussions/learners/learner/LearnerCard.jsx

@@ -1,10 +1,7 @@
 import React, { useContext } from 'react';
-import PropTypes from 'prop-types';
 
 import { Link } from 'react-router-dom';
 
-import { injectIntl } from '@edx/frontend-platform/i18n';
-
 import { Routes } from '../../../data/constants';
 import { DiscussionContext } from '../../common/context';
 import { discussionsPath } from '../../utils';
@@ -12,11 +9,11 @@ import LearnerAvatar from './LearnerAvatar';
 import LearnerFooter from './LearnerFooter';
 import { learnerShape } from './proptypes';
 
-function LearnerCard({
+const LearnerCard = ({ learner }) => {
-  learner,
+  const {
-  courseId,
+    username, threads, inactiveFlags, activeFlags, responses, replies,
-}) {
+  } = learner;
-  const { enableInContextSidebar, learnerUsername } = useContext(DiscussionContext);
+  const { enableInContextSidebar, learnerUsername, courseId } = useContext(DiscussionContext);
   const linkUrl = discussionsPath(Routes.LEARNERS.POSTS, {
     0: enableInContextSidebar ? 'in-context' : undefined,
     learnerUsername: learner.username,
@@ -30,32 +27,40 @@ function LearnerCard({
     >
       <div
         className="d-flex flex-row flex-fill mw-100 py-3 px-4 border-primary-500"
-        style={learner.username === learnerUsername ? {
+        style={username === learnerUsername ? {
           borderRightWidth: '4px',
           borderRightStyle: 'solid',
         } : null}
       >
-        <LearnerAvatar learner={learner} />
+        <LearnerAvatar username={username} />
         <div className="d-flex flex-column flex-fill" style={{ minWidth: 0 }}>
           <div className="d-flex flex-column justify-content-start mw-100 flex-fill">
             <div className="d-flex align-items-center flex-fill">
               <div
                 className="text-truncate font-weight-500 font-size-14 text-primary-500 font-style"
               >
-                {learner.username}
+                {username}
               </div>
             </div>
-            {learner.threads === null ? null : <LearnerFooter learner={learner} /> }
+            {threads !== null && (
+              <LearnerFooter
+                inactiveFlags={inactiveFlags}
+                activeFlags={activeFlags}
+                threads={threads}
+                responses={responses}
+                replies={replies}
+                username={username}
+              />
+            )}
           </div>
         </div>
       </div>
     </Link>
   );
-}
+};
 
 LearnerCard.propTypes = {
   learner: learnerShape.isRequired,
-  courseId: PropTypes.string.isRequired,
 };
 
-export default injectIntl(LearnerCard);
+export default React.memo(LearnerCard);

src/discussions/learners/learner/LearnerFilterBar.jsx

@@ -1,11 +1,11 @@
-import React, { useState } from 'react';
+import React, { useCallback, useState } from 'react';
 import PropTypes from 'prop-types';
 
 import classNames from 'classnames';
 import { useDispatch, useSelector } from 'react-redux';
 
 import { sendTrackEvent } from '@edx/frontend-platform/analytics';
-import { injectIntl, intlShape } from '@edx/frontend-platform/i18n';
+import { useIntl } from '@edx/frontend-platform/i18n';
 import { Collapsible, Form, Icon } from '@edx/paragon';
 import { Check, Tune } from '@edx/paragon/icons';
 
@@ -15,7 +15,7 @@ import { setSortedBy } from '../data';
 import { selectLearnerSorting } from '../data/selectors';
 import messages from '../messages';
 
-const ActionItem = ({
+const ActionItem = React.memo(({
   id,
   label,
   value,
@@ -38,7 +38,7 @@ const ActionItem = ({
       {label}
     </span>
   </label>
-);
+));
 
 ActionItem.propTypes = {
   id: PropTypes.string.isRequired,
@@ -47,16 +47,15 @@ ActionItem.propTypes = {
   selected: PropTypes.string.isRequired,
 };
 
-function LearnerFilterBar({
+const LearnerFilterBar = () => {
-  intl,
+  const intl = useIntl();
-}) {
   const dispatch = useDispatch();
   const userHasModerationPrivileges = useSelector(selectUserHasModerationPrivileges);
   const userIsGroupTa = useSelector(selectUserIsGroupTa);
   const currentSorting = useSelector(selectLearnerSorting());
   const [isOpen, setOpen] = useState(false);
 
-  const handleSortFilterChange = (event) => {
+  const handleSortFilterChange = useCallback((event) => {
     const { name, value } = event.currentTarget;
 
     if (name === 'sort') {
@@ -68,12 +67,16 @@ function LearnerFilterBar({
         },
       );
     }
-  };
+  }, []);
+
+  const handleOnToggle = useCallback(() => {
+    setOpen(!isOpen);
+  }, [isOpen]);
 
   return (
     <Collapsible.Advanced
       open={isOpen}
-      onToggle={() => setOpen(!isOpen)}
+      onToggle={handleOnToggle}
       className="filter-bar collapsible-card-lg border-0"
     >
       <Collapsible.Trigger className="collapsible-trigger border-0">
@@ -124,10 +127,6 @@ function LearnerFilterBar({
       </Collapsible.Body>
     </Collapsible.Advanced>
   );
-}
-
-LearnerFilterBar.propTypes = {
-  intl: intlShape.isRequired,
 };
 
-export default injectIntl(LearnerFilterBar);
+export default LearnerFilterBar;

src/discussions/learners/learner/LearnerFooter.jsx

@@ -1,24 +1,22 @@
 import React from 'react';
+import PropTypes from 'prop-types';
 
 import { useSelector } from 'react-redux';
 
-import { injectIntl, intlShape } from '@edx/frontend-platform/i18n';
+import { useIntl } from '@edx/frontend-platform/i18n';
 import { Icon, OverlayTrigger, Tooltip } from '@edx/paragon';
 import { Edit, Report, ReportGmailerrorred } from '@edx/paragon/icons';
 
 import { QuestionAnswerOutline } from '../../../components/icons';
 import { selectUserHasModerationPrivileges, selectUserIsGroupTa } from '../../data/selectors';
 import messages from '../messages';
-import { learnerShape } from './proptypes';
 
-function LearnerFooter({
+const LearnerFooter = ({
-  learner,
+  inactiveFlags, activeFlags, threads, responses, replies, username,
-  intl,
+}) => {
-}) {
+  const intl = useIntl();
   const userHasModerationPrivileges = useSelector(selectUserHasModerationPrivileges);
   const userIsGroupTa = useSelector(selectUserIsGroupTa);
-  const { inactiveFlags } = learner;
-  const { activeFlags } = learner;
   const canSeeLearnerReportedStats = (activeFlags || inactiveFlags) && (userHasModerationPrivileges || userIsGroupTa);
 
   return (
@@ -35,7 +33,7 @@ function LearnerFooter({
       >
         <div className="d-flex align-items-center">
           <Icon src={QuestionAnswerOutline} className="icon-size mr-2" />
-          {learner.threads + learner.responses + learner.replies}
+          {threads + responses + replies}
         </div>
       </OverlayTrigger>
       <OverlayTrigger
@@ -50,14 +48,14 @@ function LearnerFooter({
       >
         <div className="d-flex align-items-center">
           <Icon src={Edit} className="icon-size mr-2 ml-4" />
-          {learner.threads}
+          {threads}
         </div>
       </OverlayTrigger>
       {Boolean(canSeeLearnerReportedStats) && (
         <OverlayTrigger
           placement="right"
           overlay={(
-            <Tooltip id={`learner-${learner.username}`}>
+            <Tooltip id={`learner-${username}`}>
               <div className="d-flex flex-column align-items-start">
                 {Boolean(activeFlags)
                   && (
@@ -83,11 +81,24 @@ function LearnerFooter({
       )}
     </div>
   );
-}
-
-LearnerFooter.propTypes = {
-  intl: intlShape.isRequired,
-  learner: learnerShape.isRequired,
 };
 
-export default injectIntl(LearnerFooter);
+LearnerFooter.propTypes = {
+  inactiveFlags: PropTypes.number,
+  activeFlags: PropTypes.number,
+  threads: PropTypes.number,
+  responses: PropTypes.number,
+  replies: PropTypes.number,
+  username: PropTypes.string,
+};
+
+LearnerFooter.defaultProps = {
+  inactiveFlags: 0,
+  activeFlags: 0,
+  threads: 0,
+  responses: 0,
+  replies: 0,
+  username: '',
+};
+
+export default React.memo(LearnerFooter);

src/discussions/navigation/breadcrumb-menu/BreadcrumbDropdown.jsx

@@ -3,22 +3,23 @@ import PropTypes from 'prop-types';
 
 import { Link } from 'react-router-dom';
 
-import { injectIntl, intlShape } from '@edx/frontend-platform/i18n';
+import { useIntl } from '@edx/frontend-platform/i18n';
 import { Dropdown, DropdownButton } from '@edx/paragon';
 
 import messages from './messages';
 
-function BreadcrumbDropdown({
+const BreadcrumbDropdown = ({
   currentItem,
-  intl,
   showAllPath,
   items,
   itemPathFunc,
   itemLabelFunc,
   itemActiveFunc,
   itemFilterFunc,
-}) {
+}) => {
+  const intl = useIntl();
   const showAllMsg = intl.formatMessage(messages.showAll);
+
   return (
     <DropdownButton
       title={itemLabelFunc(currentItem) || showAllMsg}
@@ -46,12 +47,11 @@ function BreadcrumbDropdown({
       ))}
     </DropdownButton>
   );
-}
+};
 
 BreadcrumbDropdown.propTypes = {
   // eslint-disable-next-line react/forbid-prop-types
   currentItem: PropTypes.any,
-  intl: intlShape.isRequired,
   showAllPath: PropTypes.func.isRequired,
   // eslint-disable-next-line react/forbid-prop-types
   items: PropTypes.array.isRequired,
@@ -60,9 +60,10 @@ BreadcrumbDropdown.propTypes = {
   itemActiveFunc: PropTypes.func.isRequired,
   itemFilterFunc: PropTypes.func,
 };
+
 BreadcrumbDropdown.defaultProps = {
   currentItem: null,
   itemFilterFunc: null,
 };
 
-export default injectIntl(BreadcrumbDropdown);
+export default React.memo(BreadcrumbDropdown);

src/discussions/navigation/breadcrumb-menu/LegacyBreadcrumbMenu.jsx

@@ -1,4 +1,4 @@
-import React from 'react';
+import React, { useCallback } from 'react';
 
 import { useSelector } from 'react-redux';
 import { useRouteMatch } from 'react-router';
@@ -13,7 +13,7 @@ import {
 import { discussionsPath } from '../../utils';
 import BreadcrumbDropdown from './BreadcrumbDropdown';
 
-function LegacyBreadcrumbMenu() {
+const LegacyBreadcrumbMenu = () => {
   const {
     params: {
       courseId,
@@ -21,7 +21,6 @@ function LegacyBreadcrumbMenu() {
       topicId: currentTopicId,
     },
   } = useRouteMatch([Routes.TOPICS.CATEGORY, Routes.TOPICS.TOPIC]);
-
   const currentTopic = useSelector(selectTopic(currentTopicId));
   const currentCategory = category || currentTopic?.categoryId;
   const decodedCurrentCategory = String(currentCategory).replace('%23', '#');
@@ -30,31 +29,68 @@ function LegacyBreadcrumbMenu() {
   const categories = useSelector(selectCategories);
   const isNonCoursewareTopic = currentTopic && !currentCategory;
 
+  const nonCoursewareItemLabel = useCallback((item) => (
+    item?.name
+  ), []);
+
+  const nonCoursewareActive = useCallback((topic) => (
+    topic?.id === currentTopicId
+  ), [currentTopicId]);
+
+  const nonCoursewareItemPath = useCallback((topic) => (
+    discussionsPath(Routes.TOPICS.TOPIC, {
+      courseId,
+      topicId: topic.id,
+    })
+  ), [courseId]);
+
+  const coursewareItemLabel = useCallback((catId) => (
+    catId
+  ), []);
+
+  const coursewareActive = useCallback((catId) => (
+    catId === currentCategory
+  ), [currentTopicId]);
+
+  const coursewareItemPath = useCallback((catId) => (
+    discussionsPath(Routes.TOPICS.CATEGORY, {
+      courseId,
+      category: catId,
+    })
+  ), [courseId]);
+
+  const categoryItemLabel = useCallback((item) => item?.name, []);
+
+  const categoryActive = useCallback((topic) => (
+    topic?.id === currentTopicId
+  ), [currentTopicId]);
+
+  const categoryItemPath = useCallback((topic) => (
+    discussionsPath(Routes.TOPICS.TOPIC, {
+      courseId,
+      topicId: topic.id,
+    })
+  ), [courseId]);
+
   return (
     <div className="breadcrumb-menu d-flex flex-row bg-light-200 box-shadow-down-1 px-2.5 py-1">
       {isNonCoursewareTopic ? (
         <BreadcrumbDropdown
           currentItem={currentTopic}
-          itemLabelFunc={(item) => item?.name}
+          itemLabelFunc={nonCoursewareItemLabel}
-          itemActiveFunc={(topic) => topic?.id === currentTopicId}
+          itemActiveFunc={nonCoursewareActive}
           items={nonCoursewareTopics}
           showAllPath={discussionsPath(Routes.TOPICS.ALL, { courseId })}
-          itemPathFunc={(topic) => discussionsPath(Routes.TOPICS.TOPIC, {
+          itemPathFunc={nonCoursewareItemPath}
-            courseId,
-            topicId: topic.id,
-          })}
         />
       ) : (
         <BreadcrumbDropdown
           currentItem={decodedCurrentCategory}
-          itemLabelFunc={(catId) => catId}
+          itemLabelFunc={coursewareItemLabel}
-          itemActiveFunc={(catId) => catId === currentCategory}
+          itemActiveFunc={coursewareActive}
           items={categories}
           showAllPath={discussionsPath(Routes.TOPICS.ALL, { courseId })}
-          itemPathFunc={(catId) => discussionsPath(Routes.TOPICS.CATEGORY, {
+          itemPathFunc={coursewareItemPath}
-            courseId,
-            category: catId,
-          })}
         />
       )}
       {currentCategory && (
@@ -62,24 +98,19 @@ function LegacyBreadcrumbMenu() {
           <div className="d-flex py-2">/</div>
           <BreadcrumbDropdown
             currentItem={currentTopic}
-            itemLabelFunc={(item) => item?.name}
+            itemLabelFunc={categoryItemLabel}
-            itemActiveFunc={(topic) => topic?.id === currentTopicId}
+            itemActiveFunc={categoryActive}
             items={topicsInCategory}
             showAllPath={discussionsPath(Routes.TOPICS.CATEGORY, {
               courseId,
               category: currentCategory,
             })}
-            itemPathFunc={(topic) => discussionsPath(Routes.TOPICS.TOPIC, {
+            itemPathFunc={categoryItemPath}
-              courseId,
-              topicId: topic.id,
-            })}
           />
         </>
       )}
     </div>
   );
-}
+};
-
-LegacyBreadcrumbMenu.propTypes = {};
 
 export default LegacyBreadcrumbMenu;

src/discussions/navigation/navigation-bar/NavigationBar.jsx

@@ -1,21 +1,23 @@
-import React from 'react';
+import React, { useContext, useMemo } from 'react';
 
-import { matchPath, useParams } from 'react-router';
+import { matchPath } from 'react-router';
 import { NavLink } from 'react-router-dom';
 
-import { injectIntl, intlShape } from '@edx/frontend-platform/i18n';
+import { useIntl } from '@edx/frontend-platform/i18n';
 import { Nav } from '@edx/paragon';
 
 import { Routes } from '../../../data/constants';
+import { DiscussionContext } from '../../common/context';
 import { useShowLearnersTab } from '../../data/hooks';
 import { discussionsPath } from '../../utils';
 import messages from './messages';
 
-function NavigationBar({ intl }) {
+const NavigationBar = () => {
-  const { courseId } = useParams();
+  const intl = useIntl();
+  const { courseId } = useContext(DiscussionContext);
   const showLearnersTab = useShowLearnersTab();
 
-  const navLinks = [
+  const navLinks = useMemo(() => ([
     {
       route: Routes.POSTS.MY_POSTS,
       labelMessage: messages.myPosts,
@@ -29,19 +31,23 @@ function NavigationBar({ intl }) {
       isActive: (match, location) => Boolean(matchPath(location.pathname, { path: Routes.TOPICS.PATH })),
       labelMessage: messages.allTopics,
     },
-  ];
+  ]), []);
-  if (showLearnersTab) {
+
-    navLinks.push({
+  useMemo(() => {
-      route: Routes.LEARNERS.PATH,
+    if (showLearnersTab) {
-      labelMessage: messages.learners,
+      navLinks.push({
-    });
+        route: Routes.LEARNERS.PATH,
-  }
+        labelMessage: messages.learners,
+      });
+    }
+  }, [showLearnersTab]);
 
   return (
-    <Nav variant="button-group" className="py-2">
+    <Nav variant="pills" className="py-2 nav-button-group">
       {navLinks.map(link => (
         <Nav.Item key={link.route}>
           <Nav.Link
+            key={link.route}
             as={NavLink}
             to={discussionsPath(link.route, { courseId })}
             isActive={link.isActive}
@@ -52,10 +58,6 @@ function NavigationBar({ intl }) {
       ))}
     </Nav>
   );
-}
-
-NavigationBar.propTypes = {
-  intl: intlShape.isRequired,
 };
 
-export default injectIntl(NavigationBar);
+export default React.memo(NavigationBar);

src/discussions/post-comments/PostCommentsView.jsx

@@ -1,14 +1,14 @@
-import React, { useContext, useEffect, useState } from 'react';
+import React, {
+  Suspense, useCallback, useContext, useEffect, useState,
+} from 'react';
 
-import { useParams } from 'react-router';
 import { useHistory, useLocation } from 'react-router-dom';
 
-import { injectIntl, intlShape } from '@edx/frontend-platform/i18n';
+import { useIntl } from '@edx/frontend-platform/i18n';
-import {
+import { Button, Icon, IconButton } from '@edx/paragon';
-  Button, Icon, IconButton, Spinner,
-} from '@edx/paragon';
 import { ArrowBack } from '@edx/paragon/icons';
 
+import Spinner from '../../components/Spinner';
 import { EndorsementStatus, PostsPages, ThreadType } from '../../data/constants';
 import { useDispatchWithState } from '../../data/hooks';
 import { DiscussionContext } from '../common/context';
@@ -18,30 +18,45 @@ import { Post } from '../posts';
 import { fetchThread } from '../posts/data/thunks';
 import { discussionsPath } from '../utils';
 import { ResponseEditor } from './comments/comment';
-import CommentsSort from './comments/CommentsSort';
-import CommentsView from './comments/CommentsView';
 import { useCommentsCount, usePost } from './data/hooks';
 import messages from './messages';
+import { PostCommentsContext } from './postCommentsContext';
 
-function PostCommentsView({ intl }) {
+const CommentsSort = React.lazy(() => import('./comments/CommentsSort'));
-  const [isLoading, submitDispatch] = useDispatchWithState();
+const CommentsView = React.lazy(() => import('./comments/CommentsView'));
-  const { postId } = useParams();
+
-  const thread = usePost(postId);
+const PostCommentsView = () => {
-  const commentsCount = useCommentsCount(postId);
+  const intl = useIntl();
   const history = useHistory();
   const location = useLocation();
   const isOnDesktop = useIsOnDesktop();
   const [addingResponse, setAddingResponse] = useState(false);
+  const [isLoading, submitDispatch] = useDispatchWithState();
   const {
-    courseId, learnerUsername, category, topicId, page, enableInContextSidebar,
+    courseId, learnerUsername, category, topicId, page, enableInContextSidebar, postId,
   } = useContext(DiscussionContext);
+  const commentsCount = useCommentsCount(postId);
+  const { closed, id: threadId, type } = usePost(postId);
 
   useEffect(() => {
-    if (!thread) { submitDispatch(fetchThread(postId, courseId, true)); }
+    if (!postId) {
-    setAddingResponse(false);
+      submitDispatch(fetchThread(postId, courseId, true));
-  }, [postId]);
+    }
 
-  if (!thread) {
+    return () => {
+      setAddingResponse(false);
+    };
+  }, [postId, courseId]);
+
+  const handleAddResponseButton = useCallback(() => {
+    setAddingResponse(true);
+  }, []);
+
+  const handleCloseEditor = useCallback(() => {
+    setAddingResponse(false);
+  }, []);
+
+  if (!threadId) {
     if (!isLoading) {
       return (
         <EmptyPage title={intl.formatMessage(messages.noThreadFound)} />
@@ -59,7 +74,12 @@ function PostCommentsView({ intl }) {
   }
 
   return (
-    <>
+    <PostCommentsContext.Provider value={{
+      isClosed: closed,
+      postType: type,
+      postId,
+    }}
+    >
       {!isOnDesktop && (
         enableInContextSidebar ? (
           <>
@@ -95,49 +115,28 @@ function PostCommentsView({ intl }) {
       <div
         className="discussion-comments d-flex flex-column card border-0 post-card-margin post-card-padding on-focus"
       >
-        <Post post={thread} handleAddResponseButton={() => setAddingResponse(true)} />
+        <Post handleAddResponseButton={handleAddResponseButton} />
-        {!thread.closed && (
+        {!closed && (
           <ResponseEditor
-            postId={postId}
+            handleCloseEditor={handleCloseEditor}
-            handleCloseEditor={() => setAddingResponse(false)}
             addingResponse={addingResponse}
           />
         )}
       </div>
-      {!!commentsCount && <CommentsSort />}
+      <Suspense fallback={(<Spinner />)}>
-      {thread.type === ThreadType.DISCUSSION && (
+        {!!commentsCount && <CommentsSort />}
-        <CommentsView
+        {type === ThreadType.DISCUSSION && (
-          postId={postId}
+          <CommentsView endorsed={EndorsementStatus.DISCUSSION} />
-          intl={intl}
+        )}
-          postType={thread.type}
+        {type === ThreadType.QUESTION && (
-          endorsed={EndorsementStatus.DISCUSSION}
+          <>
-          isClosed={thread.closed}
+            <CommentsView endorsed={EndorsementStatus.ENDORSED} />
-        />
+            <CommentsView endorsed={EndorsementStatus.UNENDORSED} />
-      )}
+          </>
-      {thread.type === ThreadType.QUESTION && (
+        )}
-        <>
+      </Suspense>
-          <CommentsView
+    </PostCommentsContext.Provider>
-            postId={postId}
-            intl={intl}
-            postType={thread.type}
-            endorsed={EndorsementStatus.ENDORSED}
-            isClosed={thread.closed}
-          />
-          <CommentsView
-            postId={postId}
-            intl={intl}
-            postType={thread.type}
-            endorsed={EndorsementStatus.UNENDORSED}
-            isClosed={thread.closed}
-          />
-        </>
-      )}
-    </>
   );
-}
-
-PostCommentsView.propTypes = {
-  intl: intlShape.isRequired,
 };
 
-export default injectIntl(PostCommentsView);
+export default PostCommentsView;

src/discussions/post-comments/comments/CommentsSort.jsx

@@ -2,7 +2,7 @@ import React, { useCallback, useEffect, useState } from 'react';
 
 import { useDispatch, useSelector } from 'react-redux';
 
-import { injectIntl, intlShape } from '@edx/frontend-platform/i18n';
+import { useIntl } from '@edx/frontend-platform/i18n';
 import {
   Button, Dropdown, ModalPopup, useToggle,
 } from '@edx/paragon';
@@ -13,15 +13,17 @@ import { selectCommentSortOrder } from '../data/selectors';
 import { setCommentSortOrder } from '../data/slices';
 import messages from '../messages';
 
-function CommentSortDropdown({ intl }) {
+const CommentSortDropdown = () => {
+  const intl = useIntl();
   const dispatch = useDispatch();
   const sortedOrder = useSelector(selectCommentSortOrder);
   const [isOpen, open, close] = useToggle(false);
   const [target, setTarget] = useState(null);
-  const handleActions = (reverseOrder) => {
+
+  const handleActions = useCallback((reverseOrder) => {
     close();
     dispatch(setCommentSortOrder(reverseOrder));
-  };
+  }, []);
 
   const enableCommentsSortTour = useCallback((enabled) => {
     const data = {
@@ -94,11 +96,6 @@ function CommentSortDropdown({ intl }) {
       </div>
     </>
   );
-}
-
-CommentSortDropdown.propTypes = {
-  intl: intlShape.isRequired,
-
 };
 
-export default injectIntl(CommentSortDropdown);
+export default CommentSortDropdown;

src/discussions/post-comments/comments/CommentsView.jsx

@@ -1,36 +1,39 @@
-import React, { useMemo, useState } from 'react';
+import React, { useCallback, useContext, useState } from 'react';
 import PropTypes from 'prop-types';
 
-import { injectIntl, intlShape } from '@edx/frontend-platform/i18n';
+import { useIntl } from '@edx/frontend-platform/i18n';
 import { Button, Spinner } from '@edx/paragon';
 
 import { EndorsementStatus } from '../../../data/constants';
 import { useUserCanAddThreadInBlackoutDate } from '../../data/hooks';
-import { filterPosts, isLastElementOfList } from '../../utils';
+import { isLastElementOfList } from '../../utils';
 import { usePostComments } from '../data/hooks';
 import messages from '../messages';
+import { PostCommentsContext } from '../postCommentsContext';
 import { Comment, ResponseEditor } from './comment';
 
-function CommentsView({
+const CommentsView = ({ endorsed }) => {
-  postType,
+  const intl = useIntl();
-  postId,
+  const [addingResponse, setAddingResponse] = useState(false);
-  intl,
+  const { isClosed } = useContext(PostCommentsContext);
-  endorsed,
+  const userCanAddThreadInBlackoutDate = useUserCanAddThreadInBlackoutDate();
-  isClosed,
-}) {
   const {
-    comments,
+    endorsedCommentsIds,
+    unEndorsedCommentsIds,
     hasMorePages,
     isLoading,
     handleLoadMoreResponses,
-  } = usePostComments(postId, endorsed);
+  } = usePostComments(endorsed);
 
-  const endorsedComments = useMemo(() => [...filterPosts(comments, 'endorsed')], [comments]);
+  const handleAddResponse = useCallback(() => {
-  const unEndorsedComments = useMemo(() => [...filterPosts(comments, 'unendorsed')], [comments]);
+    setAddingResponse(true);
-  const userCanAddThreadInBlackoutDate = useUserCanAddThreadInBlackoutDate();
+  }, []);
-  const [addingResponse, setAddingResponse] = useState(false);
 
-  const handleDefinition = (message, commentsLength) => (
+  const handleCloseResponseEditor = useCallback(() => {
+    setAddingResponse(false);
+  }, []);
+
+  const handleDefinition = useCallback((message, commentsLength) => (
     <div
       className="mx-4 my-14px text-gray-700 font-style"
       role="heading"
@@ -38,17 +41,15 @@ function CommentsView({
     >
       {intl.formatMessage(message, { num: commentsLength })}
     </div>
-  );
+  ), []);
 
-  const handleComments = (postComments, showLoadMoreResponses = false) => (
+  const handleComments = useCallback((postCommentsIds, showLoadMoreResponses = false) => (
     <div className="mx-4" role="list">
-      {postComments.map((comment) => (
+      {postCommentsIds.map((commentId) => (
         <Comment
-          comment={comment}
+          commentId={commentId}
-          key={comment.id}
+          key={commentId}
-          postType={postType}
+          marginBottom={isLastElementOfList(postCommentsIds, commentId)}
-          isClosedPost={isClosed}
-          marginBottom={isLastElementOfList(postComments, comment)}
         />
       ))}
       {hasMorePages && !isLoading && !showLoadMoreResponses && (
@@ -68,26 +69,26 @@ function CommentsView({
         </div>
       )}
     </div>
-  );
+  ), [hasMorePages, isLoading, handleLoadMoreResponses]);
 
   return (
     <>
       {((hasMorePages && isLoading) || !isLoading) && (
         <>
-          {endorsedComments.length > 0 && (
+          {endorsedCommentsIds.length > 0 && (
             <>
-              {handleDefinition(messages.endorsedResponseCount, endorsedComments.length)}
+              {handleDefinition(messages.endorsedResponseCount, endorsedCommentsIds.length)}
               {endorsed === EndorsementStatus.DISCUSSION
-                ? handleComments(endorsedComments, true)
+                ? handleComments(endorsedCommentsIds, true)
-                : handleComments(endorsedComments, false)}
+                : handleComments(endorsedCommentsIds, false)}
             </>
           )}
           {endorsed !== EndorsementStatus.ENDORSED && (
             <>
-              {handleDefinition(messages.responseCount, unEndorsedComments.length)}
+              {handleDefinition(messages.responseCount, unEndorsedCommentsIds.length)}
-              {unEndorsedComments.length === 0 && <br />}
+              {unEndorsedCommentsIds.length === 0 && <br />}
-              {handleComments(unEndorsedComments, false)}
+              {handleComments(unEndorsedCommentsIds, false)}
-              {(userCanAddThreadInBlackoutDate && !!unEndorsedComments.length && !isClosed) && (
+              {(userCanAddThreadInBlackoutDate && !!unEndorsedCommentsIds.length && !isClosed) && (
                 <div className="mx-4">
                   {!addingResponse && (
                     <Button
@@ -95,17 +96,16 @@ function CommentsView({
                       block="true"
                       className="card mb-4 px-0 border-0 py-10px mt-2 font-style font-weight-500
                       line-height-24 font-size-14 text-primary-500"
-                      onClick={() => setAddingResponse(true)}
+                      onClick={handleAddResponse}
                       data-testid="add-response"
                     >
                       {intl.formatMessage(messages.addResponse)}
                     </Button>
                   )}
                   <ResponseEditor
-                    postId={postId}
-                    handleCloseEditor={() => setAddingResponse(false)}
                     addWrappingDiv
                     addingResponse={addingResponse}
+                    handleCloseEditor={handleCloseResponseEditor}
                   />
                 </div>
               )}
@@ -115,16 +115,12 @@ function CommentsView({
       )}
     </>
   );
-}
+};
 
 CommentsView.propTypes = {
-  postId: PropTypes.string.isRequired,
-  postType: PropTypes.string.isRequired,
-  isClosed: PropTypes.bool.isRequired,
-  intl: intlShape.isRequired,
   endorsed: PropTypes.oneOf([
     EndorsementStatus.ENDORSED, EndorsementStatus.UNENDORSED, EndorsementStatus.DISCUSSION,
   ]).isRequired,
 };
 
-export default injectIntl(CommentsView);
+export default React.memo(CommentsView);

src/discussions/post-comments/comments/comment/Comment.jsx

@@ -1,13 +1,12 @@
 import React, {
-  useCallback,
+  useCallback, useContext, useEffect, useMemo, useState,
-  useContext, useEffect, useMemo, useState,
 } from 'react';
 import PropTypes from 'prop-types';
 
 import classNames from 'classnames';
 import { useDispatch, useSelector } from 'react-redux';
 
-import { injectIntl, intlShape } from '@edx/frontend-platform/i18n';
+import { useIntl } from '@edx/frontend-platform/i18n';
 import { Button, useToggle } from '@edx/paragon';
 
 import HTMLLoader from '../../../../components/HTMLLoader';
@@ -15,6 +14,7 @@ import { ContentActions, EndorsementStatus } from '../../../../data/constants';
 import { AlertBanner, Confirmation, EndorsedAlertBanner } from '../../../common';
 import { DiscussionContext } from '../../../common/context';
 import HoverCard from '../../../common/HoverCard';
+import { ContentTypes } from '../../../data/constants';
 import { useUserCanAddThreadInBlackoutDate } from '../../../data/hooks';
 import { fetchThread } from '../../../posts/data/thunks';
 import LikeButton from '../../../posts/post/LikeButton';
@@ -22,88 +22,123 @@ import { useActions } from '../../../utils';
 import {
   selectCommentCurrentPage,
   selectCommentHasMorePages,
+  selectCommentOrResponseById,
   selectCommentResponses,
+  selectCommentResponsesIds,
   selectCommentSortOrder,
 } from '../../data/selectors';
 import { editComment, fetchCommentResponses, removeComment } from '../../data/thunks';
 import messages from '../../messages';
+import { PostCommentsContext } from '../../postCommentsContext';
 import CommentEditor from './CommentEditor';
 import CommentHeader from './CommentHeader';
-import { commentShape } from './proptypes';
 import Reply from './Reply';
 
-function Comment({
+const Comment = ({
-  postType,
+  commentId,
-  comment,
-  showFullThread = true,
-  isClosedPost,
-  intl,
   marginBottom,
-}) {
+  showFullThread = true,
+}) => {
+  const comment = useSelector(selectCommentOrResponseById(commentId));
+  const {
+    id, parentId, childCount, abuseFlagged, endorsed, threadId, endorsedAt, endorsedBy, endorsedByLabel, renderedBody,
+    voted, following, voteCount, authorLabel, author, createdAt, lastEdit, rawBody, closed, closedBy, closeReason,
+    editByLabel, closedByLabel,
+  } = comment;
+  const intl = useIntl();
+  const hasChildren = childCount > 0;
+  const isNested = Boolean(parentId);
   const dispatch = useDispatch();
-  const hasChildren = comment.childCount > 0;
+  const { courseId } = useContext(DiscussionContext);
-  const isNested = Boolean(comment.parentId);
+  const { isClosed } = useContext(PostCommentsContext);
-  const inlineReplies = useSelector(selectCommentResponses(comment.id));
   const [isEditing, setEditing] = useState(false);
+  const [isReplying, setReplying] = useState(false);
   const [isDeleting, showDeleteConfirmation, hideDeleteConfirmation] = useToggle(false);
   const [isReporting, showReportConfirmation, hideReportConfirmation] = useToggle(false);
-  const [isReplying, setReplying] = useState(false);
+  const inlineReplies = useSelector(selectCommentResponses(id));
-  const hasMorePages = useSelector(selectCommentHasMorePages(comment.id));
+  const inlineRepliesIds = useSelector(selectCommentResponsesIds(id));
-  const currentPage = useSelector(selectCommentCurrentPage(comment.id));
+  const hasMorePages = useSelector(selectCommentHasMorePages(id));
-  const userCanAddThreadInBlackoutDate = useUserCanAddThreadInBlackoutDate();
+  const currentPage = useSelector(selectCommentCurrentPage(id));
-  const { courseId } = useContext(DiscussionContext);
   const sortedOrder = useSelector(selectCommentSortOrder);
+  const actions = useActions(ContentTypes.COMMENT, id);
+  const userCanAddThreadInBlackoutDate = useUserCanAddThreadInBlackoutDate();
 
   useEffect(() => {
     // If the comment has a parent comment, it won't have any children, so don't fetch them.
     if (hasChildren && showFullThread) {
-      dispatch(fetchCommentResponses(comment.id, {
+      dispatch(fetchCommentResponses(id, {
         page: 1,
         reverseOrder: sortedOrder,
       }));
     }
-  }, [comment.id, sortedOrder]);
+  }, [id, sortedOrder]);
 
-  const actions = useActions({
+  const endorseIcons = useMemo(() => (
-    ...comment,
+    actions.find(({ action }) => action === EndorsementStatus.ENDORSED)
-    postType,
+  ), [actions]);
-  });
+
-  const endorseIcons = actions.find(({ action }) => action === EndorsementStatus.ENDORSED);
+  const handleEditContent = useCallback(() => {
+    setEditing(true);
+  }, []);
+
+  const handleCommentEndorse = useCallback(async () => {
+    await dispatch(editComment(id, { endorsed: !endorsed }, ContentActions.ENDORSE));
+    await dispatch(fetchThread(threadId, courseId));
+  }, [id, endorsed, threadId]);
 
   const handleAbusedFlag = useCallback(() => {
-    if (comment.abuseFlagged) {
+    if (abuseFlagged) {
-      dispatch(editComment(comment.id, { flagged: !comment.abuseFlagged }));
+      dispatch(editComment(id, { flagged: !abuseFlagged }));
     } else {
       showReportConfirmation();
     }
-  }, [comment.abuseFlagged, comment.id, dispatch, showReportConfirmation]);
+  }, [abuseFlagged, id, showReportConfirmation]);
 
-  const handleDeleteConfirmation = () => {
+  const handleDeleteConfirmation = useCallback(() => {
-    dispatch(removeComment(comment.id));
+    dispatch(removeComment(id));
     hideDeleteConfirmation();
-  };
+  }, [id, hideDeleteConfirmation]);
 
-  const handleReportConfirmation = () => {
+  const handleReportConfirmation = useCallback(() => {
-    dispatch(editComment(comment.id, { flagged: !comment.abuseFlagged }));
+    dispatch(editComment(id, { flagged: !abuseFlagged }));
     hideReportConfirmation();
-  };
+  }, [abuseFlagged, id, hideReportConfirmation]);
 
   const actionHandlers = useMemo(() => ({
-    [ContentActions.EDIT_CONTENT]: () => setEditing(true),
+    [ContentActions.EDIT_CONTENT]: handleEditContent,
-    [ContentActions.ENDORSE]: async () => {
+    [ContentActions.ENDORSE]: handleCommentEndorse,
-      await dispatch(editComment(comment.id, { endorsed: !comment.endorsed }, ContentActions.ENDORSE));
-      await dispatch(fetchThread(comment.threadId, courseId));
-    },
     [ContentActions.DELETE]: showDeleteConfirmation,
-    [ContentActions.REPORT]: () => handleAbusedFlag(),
+    [ContentActions.REPORT]: handleAbusedFlag,
-  }), [showDeleteConfirmation, dispatch, comment.id, comment.endorsed, comment.threadId, courseId, handleAbusedFlag]);
+  }), [handleEditContent, handleCommentEndorse, showDeleteConfirmation, handleAbusedFlag]);
 
-  const handleLoadMoreComments = () => (
+  const handleLoadMoreComments = useCallback(() => (
-    dispatch(fetchCommentResponses(comment.id, {
+    dispatch(fetchCommentResponses(id, {
       page: currentPage + 1,
       reverseOrder: sortedOrder,
     }))
-  );
+  ), [id, currentPage, sortedOrder]);
+
+  const handleAddCommentButton = useCallback(() => {
+    if (userCanAddThreadInBlackoutDate) {
+      setReplying(true);
+    }
+  }, [userCanAddThreadInBlackoutDate]);
+
+  const handleCommentLike = useCallback(async () => {
+    await dispatch(editComment(id, { voted: !voted }));
+  }, [id, voted]);
+
+  const handleCloseEditor = useCallback(() => {
+    setEditing(false);
+  }, []);
+
+  const handleAddCommentReply = useCallback(() => {
+    setReplying(true);
+  }, []);
+
+  const handleCloseReplyEditor = useCallback(() => {
+    setReplying(false);
+  }, []);
 
   return (
     <div className={classNames({ 'mb-3': (showFullThread && !marginBottom) })}>
@@ -111,7 +146,7 @@ function Comment({
       <div
         tabIndex="0"
         className="d-flex flex-column card on-focus border-0"
-        data-testid={`comment-${comment.id}`}
+        data-testid={`comment-${id}`}
         role="listitem"
       >
         <Confirmation
@@ -123,7 +158,7 @@ function Comment({
           closeButtonVaraint="tertiary"
           confirmButtonText={intl.formatMessage(messages.deleteConfirmationDelete)}
         />
-        {!comment.abuseFlagged && (
+        {!abuseFlagged && (
           <Confirmation
             isOpen={isReporting}
             title={intl.formatMessage(messages.reportResponseTitle)}
@@ -133,49 +168,78 @@ function Comment({
             confirmButtonVariant="danger"
           />
         )}
-        <EndorsedAlertBanner postType={postType} content={comment} />
+        <EndorsedAlertBanner
+          endorsed={endorsed}
+          endorsedAt={endorsedAt}
+          endorsedBy={endorsedBy}
+          endorsedByLabel={endorsedByLabel}
+        />
         <div className="d-flex flex-column post-card-comment px-4 pt-3.5 pb-10px" tabIndex="0">
           <HoverCard
-            commentOrPost={comment}
+            id={id}
+            contentType={ContentTypes.COMMENT}
             actionHandlers={actionHandlers}
-            handleResponseCommentButton={() => setReplying(true)}
+            handleResponseCommentButton={handleAddCommentButton}
-            onLike={() => dispatch(editComment(comment.id, { voted: !comment.voted }))}
             addResponseCommentButtonMessage={intl.formatMessage(messages.addComment)}
-            isClosedPost={isClosedPost}
+            onLike={handleCommentLike}
+            voted={voted}
+            following={following}
             endorseIcons={endorseIcons}
           />
-          <AlertBanner content={comment} />
+          <AlertBanner
-          <CommentHeader comment={comment} />
+            author={author}
-          {isEditing
+            abuseFlagged={abuseFlagged}
-            ? (
+            lastEdit={lastEdit}
-              <CommentEditor comment={comment} onCloseEditor={() => setEditing(false)} formClasses="pt-3" />
+            closed={closed}
-            )
+            closedBy={closedBy}
-            : (
+            closeReason={closeReason}
-              <HTMLLoader
+            editByLabel={editByLabel}
-                cssClassName="comment-body html-loader text-break mt-14px font-style text-primary-500"
+            closedByLabel={closedByLabel}
-                componentId="comment"
+          />
-                htmlNode={comment.renderedBody}
+          <CommentHeader
-                testId={comment.id}
+            author={author}
-              />
+            authorLabel={authorLabel}
-            )}
+            abuseFlagged={abuseFlagged}
-          {comment.voted && (
+            closed={closed}
+            createdAt={createdAt}
+            lastEdit={lastEdit}
+          />
+          {isEditing ? (
+            <CommentEditor
+              comment={{
+                author,
+                id,
+                lastEdit,
+                threadId,
+                parentId,
+                rawBody,
+              }}
+              onCloseEditor={handleCloseEditor}
+              formClasses="pt-3"
+            />
+          ) : (
+            <HTMLLoader
+              cssClassName="comment-body html-loader text-break mt-14px font-style text-primary-500"
+              componentId="comment"
+              htmlNode={renderedBody}
+              testId={id}
+            />
+          )}
+          {voted && (
             <div className="ml-n1.5 mt-10px">
               <LikeButton
-                count={comment.voteCount}
+                count={voteCount}
-                onClick={() => dispatch(editComment(comment.id, { voted: !comment.voted }))}
+                onClick={handleCommentLike}
-                voted={comment.voted}
+                voted={voted}
               />
             </div>
           )}
-          {inlineReplies.length > 0 && (
+          {inlineRepliesIds.length > 0 && (
             <div className="d-flex flex-column mt-0.5" role="list">
-              {/* Pass along intl since component used here is the one before it's injected with `injectIntl` */}
+              {inlineRepliesIds.map(replyId => (
-              {inlineReplies.map(inlineReply => (
                 <Reply
-                  reply={inlineReply}
+                  responseId={replyId}
-                  postType={postType}
+                  key={replyId}
-                  key={inlineReply.id}
-                  intl={intl}
                 />
               ))}
             </div>
@@ -195,46 +259,39 @@ function Comment({
             isReplying ? (
               <div className="mt-2.5">
                 <CommentEditor
-                  comment={{ threadId: comment.threadId, parentId: comment.id }}
+                  comment={{ threadId, parentId: id }}
                   edit={false}
-                  onCloseEditor={() => setReplying(false)}
+                  onCloseEditor={handleCloseReplyEditor}
                 />
               </div>
             ) : (
-              <>
+              !isClosed && userCanAddThreadInBlackoutDate && (inlineReplies.length >= 5) && (
-                {!isClosedPost && userCanAddThreadInBlackoutDate && (inlineReplies.length >= 5)
+                <Button
-                  && (
+                  className="d-flex flex-grow mt-2 font-size-14 font-style font-weight-500 text-primary-500"
-                    <Button
+                  variant="plain"
-                      className="d-flex flex-grow mt-2 font-size-14 font-style font-weight-500 text-primary-500"
+                  style={{ height: '36px' }}
-                      variant="plain"
+                  onClick={handleAddCommentReply}
-                      style={{ height: '36px' }}
+                >
-                      onClick={() => setReplying(true)}
+                  {intl.formatMessage(messages.addComment)}
-                    >
+                </Button>
-                      {intl.formatMessage(messages.addComment)}
+              )
-                    </Button>
-                  )}
-              </>
             )
           )}
         </div>
       </div>
     </div>
   );
-}
+};
 
 Comment.propTypes = {
-  postType: PropTypes.oneOf(['discussion', 'question']).isRequired,
+  commentId: PropTypes.string.isRequired,
-  comment: commentShape.isRequired,
-  showFullThread: PropTypes.bool,
-  isClosedPost: PropTypes.bool,
-  intl: intlShape.isRequired,
   marginBottom: PropTypes.bool,
+  showFullThread: PropTypes.bool,
 };
 
 Comment.defaultProps = {
+  marginBottom: false,
   showFullThread: true,
-  isClosedPost: false,
-  marginBottom: true,
 };
 
-export default injectIntl(Comment);
+export default React.memo(Comment);

src/discussions/post-comments/comments/comment/CommentEditor.jsx

@@ -1,11 +1,11 @@
-import React, { useContext, useRef } from 'react';
+import React, { useCallback, useContext, useRef } from 'react';
 import PropTypes from 'prop-types';
 
 import { Formik } from 'formik';
 import { useSelector } from 'react-redux';
 import * as Yup from 'yup';
 
-import { injectIntl, intlShape } from '@edx/frontend-platform/i18n';
+import { useIntl } from '@edx/frontend-platform/i18n';
 import { AppContext } from '@edx/frontend-platform/react';
 import { Button, Form, StatefulButton } from '@edx/paragon';
 
@@ -25,12 +25,15 @@ import { addComment, editComment } from '../../data/thunks';
 import messages from '../../messages';
 
 function CommentEditor({
-  intl,
   comment,
-  onCloseEditor,
   edit,
   formClasses,
+  onCloseEditor,
 }) {
+  const {
+    id, threadId, parentId, rawBody, author, lastEdit,
+  } = comment;
+  const intl = useIntl();
   const editorRef = useRef(null);
   const { authenticatedUser } = useContext(AppContext);
   const { enableInContextSidebar } = useContext(DiscussionContext);
@@ -42,7 +45,7 @@ function CommentEditor({
 
   const canDisplayEditReason = (reasonCodesEnabled && edit
     && (userHasModerationPrivileges || userIsGroupTa || userIsStaff)
-    && comment?.author !== authenticatedUser.username
+    && author !== authenticatedUser.username
   );
 
   const editReasonCodeValidation = canDisplayEditReason && {
@@ -56,34 +59,34 @@ function CommentEditor({
   });
 
   const initialValues = {
-    comment: comment.rawBody,
+    comment: rawBody,
-    editReasonCode: comment?.lastEdit?.reasonCode || (userIsStaff ? 'violates-guidelines' : ''),
+    editReasonCode: lastEdit?.reasonCode || (userIsStaff ? 'violates-guidelines' : ''),
   };
 
-  const handleCloseEditor = (resetForm) => {
+  const handleCloseEditor = useCallback((resetForm) => {
     resetForm({ values: initialValues });
     onCloseEditor();
-  };
+  }, [onCloseEditor, initialValues]);
 
-  const saveUpdatedComment = async (values, { resetForm }) => {
+  const saveUpdatedComment = useCallback(async (values, { resetForm }) => {
-    if (comment.id) {
+    if (id) {
       const payload = {
         ...values,
         editReasonCode: values.editReasonCode || undefined,
       };
-      await dispatch(editComment(comment.id, payload));
+      await dispatch(editComment(id, payload));
     } else {
-      await dispatch(addComment(values.comment, comment.threadId, comment.parentId, enableInContextSidebar));
+      await dispatch(addComment(values.comment, threadId, parentId, enableInContextSidebar));
     }
     /* istanbul ignore if: TinyMCE is mocked so this cannot be easily tested */
     if (editorRef.current) {
       editorRef.current.plugins.autosave.removeDraft();
     }
     handleCloseEditor(resetForm);
-  };
+  }, [id, threadId, parentId, enableInContextSidebar, handleCloseEditor]);
   // The editorId is used to autosave contents to localstorage. This format means that the autosave is scoped to
   // the current comment id, or the current comment parent or the curren thread.
-  const editorId = `comment-editor-${comment.id || comment.parentId || comment.threadId}`;
+  const editorId = `comment-editor-${id || parentId || threadId}`;
 
   return (
     <Formik
@@ -177,22 +180,28 @@ function CommentEditor({
 
 CommentEditor.propTypes = {
   comment: PropTypes.shape({
+    author: PropTypes.string,
     id: PropTypes.string,
-    threadId: PropTypes.string.isRequired,
+    lastEdit: PropTypes.object,
     parentId: PropTypes.string,
     rawBody: PropTypes.string,
-    author: PropTypes.string,
+    threadId: PropTypes.string.isRequired,
-    lastEdit: PropTypes.object,
+  }),
-  }).isRequired,
-  onCloseEditor: PropTypes.func.isRequired,
-  intl: intlShape.isRequired,
   edit: PropTypes.bool,
   formClasses: PropTypes.string,
+  onCloseEditor: PropTypes.func.isRequired,
 };
 
 CommentEditor.defaultProps = {
   edit: true,
+  comment: {
+    author: null,
+    id: null,
+    lastEdit: null,
+    parentId: null,
+    rawBody: '',
+  },
   formClasses: '',
 };
 
-export default injectIntl(CommentEditor);
+export default React.memo(CommentEditor);

src/discussions/post-comments/comments/comment/CommentHeader.jsx

@@ -1,20 +1,29 @@
 import React from 'react';
+import PropTypes from 'prop-types';
 
 import classNames from 'classnames';
 
-import { injectIntl } from '@edx/frontend-platform/i18n';
 import { Avatar } from '@edx/paragon';
 
 import { AvatarOutlineAndLabelColors } from '../../../../data/constants';
 import { AuthorLabel } from '../../../common';
 import { useAlertBannerVisible } from '../../../data/hooks';
-import { commentShape } from './proptypes';
 
-function CommentHeader({
+const CommentHeader = ({
-  comment,
+  author,
-}) {
+  authorLabel,
-  const colorClass = AvatarOutlineAndLabelColors[comment.authorLabel];
+  abuseFlagged,
-  const hasAnyAlert = useAlertBannerVisible(comment);
+  closed,
+  createdAt,
+  lastEdit,
+}) => {
+  const colorClass = AvatarOutlineAndLabelColors[authorLabel];
+  const hasAnyAlert = useAlertBannerVisible({
+    author,
+    abuseFlagged,
+    lastEdit,
+    closed,
+  });
 
   return (
     <div className={classNames('d-flex flex-row justify-content-between', {
@@ -24,27 +33,41 @@ function CommentHeader({
       <div className="align-items-center d-flex flex-row">
         <Avatar
           className={`border-0 ml-0.5 mr-2.5 ${colorClass ? `outline-${colorClass}` : 'outline-anonymous'}`}
-          alt={comment.author}
+          alt={author}
           style={{
             width: '32px',
             height: '32px',
           }}
         />
         <AuthorLabel
-          author={comment.author}
+          author={author}
-          authorLabel={comment.authorLabel}
+          authorLabel={authorLabel}
           labelColor={colorClass && `text-${colorClass}`}
           linkToProfile
-          postCreatedAt={comment.createdAt}
+          postCreatedAt={createdAt}
           postOrComment
         />
       </div>
     </div>
   );
-}
-
-CommentHeader.propTypes = {
-  comment: commentShape.isRequired,
 };
 
-export default injectIntl(CommentHeader);
+CommentHeader.propTypes = {
+  author: PropTypes.string.isRequired,
+  authorLabel: PropTypes.string,
+  abuseFlagged: PropTypes.bool.isRequired,
+  closed: PropTypes.bool,
+  createdAt: PropTypes.string.isRequired,
+  lastEdit: PropTypes.shape({
+    editorUsername: PropTypes.string,
+    reason: PropTypes.string,
+  }),
+};
+
+CommentHeader.defaultProps = {
+  authorLabel: null,
+  closed: undefined,
+  lastEdit: null,
+};
+
+export default React.memo(CommentHeader);

src/discussions/post-comments/comments/comment/Reply.jsx

@@ -1,10 +1,10 @@
 import React, { useCallback, useMemo, useState } from 'react';
 import PropTypes from 'prop-types';
 
-import { useDispatch } from 'react-redux';
+import { useDispatch, useSelector } from 'react-redux';
 import * as timeago from 'timeago.js';
 
-import { injectIntl, intlShape } from '@edx/frontend-platform/i18n';
+import { useIntl } from '@edx/frontend-platform/i18n';
 import { Avatar, useToggle } from '@edx/paragon';
 
 import HTMLLoader from '../../../../components/HTMLLoader';
@@ -13,57 +13,71 @@ import {
   ActionsDropdown, AlertBanner, AuthorLabel, Confirmation,
 } from '../../../common';
 import timeLocale from '../../../common/time-locale';
+import { ContentTypes } from '../../../data/constants';
 import { useAlertBannerVisible } from '../../../data/hooks';
+import { selectCommentOrResponseById } from '../../data/selectors';
 import { editComment, removeComment } from '../../data/thunks';
 import messages from '../../messages';
 import CommentEditor from './CommentEditor';
-import { commentShape } from './proptypes';
 
-function Reply({
+const Reply = ({ responseId }) => {
-  reply,
-  postType,
-  intl,
-}) {
   timeago.register('time-locale', timeLocale);
+  const {
+    id, abuseFlagged, author, authorLabel, endorsed, lastEdit, closed, closedBy,
+    closeReason, createdAt, threadId, parentId, rawBody, renderedBody, editByLabel, closedByLabel,
+  } = useSelector(selectCommentOrResponseById(responseId));
+  const intl = useIntl();
   const dispatch = useDispatch();
   const [isEditing, setEditing] = useState(false);
   const [isDeleting, showDeleteConfirmation, hideDeleteConfirmation] = useToggle(false);
   const [isReporting, showReportConfirmation, hideReportConfirmation] = useToggle(false);
+  const colorClass = AvatarOutlineAndLabelColors[authorLabel];
+  const hasAnyAlert = useAlertBannerVisible({
+    author,
+    abuseFlagged,
+    lastEdit,
+    closed,
+  });
+
+  const handleDeleteConfirmation = useCallback(() => {
+    dispatch(removeComment(id));
+    hideDeleteConfirmation();
+  }, [id, hideDeleteConfirmation]);
+
+  const handleReportConfirmation = useCallback(() => {
+    dispatch(editComment(id, { flagged: !abuseFlagged }));
+    hideReportConfirmation();
+  }, [abuseFlagged, id, hideReportConfirmation]);
+
+  const handleEditContent = useCallback(() => {
+    setEditing(true);
+  }, []);
+
+  const handleReplyEndorse = useCallback(() => {
+    dispatch(editComment(id, { endorsed: !endorsed }, ContentActions.ENDORSE));
+  }, [endorsed, id]);
 
   const handleAbusedFlag = useCallback(() => {
-    if (reply.abuseFlagged) {
+    if (abuseFlagged) {
-      dispatch(editComment(reply.id, { flagged: !reply.abuseFlagged }));
+      dispatch(editComment(id, { flagged: !abuseFlagged }));
     } else {
       showReportConfirmation();
     }
-  }, [dispatch, reply.abuseFlagged, reply.id, showReportConfirmation]);
+  }, [abuseFlagged, id, showReportConfirmation]);
 
-  const handleDeleteConfirmation = () => {
+  const handleCloseEditor = useCallback(() => {
-    dispatch(removeComment(reply.id));
+    setEditing(false);
-    hideDeleteConfirmation();
+  }, []);
-  };
-
-  const handleReportConfirmation = () => {
-    dispatch(editComment(reply.id, { flagged: !reply.abuseFlagged }));
-    hideReportConfirmation();
-  };
 
   const actionHandlers = useMemo(() => ({
-    [ContentActions.EDIT_CONTENT]: () => setEditing(true),
+    [ContentActions.EDIT_CONTENT]: handleEditContent,
-    [ContentActions.ENDORSE]: () => dispatch(editComment(
+    [ContentActions.ENDORSE]: handleReplyEndorse,
-      reply.id,
-      { endorsed: !reply.endorsed },
-      ContentActions.ENDORSE,
-    )),
     [ContentActions.DELETE]: showDeleteConfirmation,
-    [ContentActions.REPORT]: () => handleAbusedFlag(),
+    [ContentActions.REPORT]: handleAbusedFlag,
-  }), [dispatch, handleAbusedFlag, reply.endorsed, reply.id, showDeleteConfirmation]);
+  }), [handleEditContent, handleReplyEndorse, showDeleteConfirmation, handleAbusedFlag]);
-
-  const colorClass = AvatarOutlineAndLabelColors[reply.authorLabel];
-  const hasAnyAlert = useAlertBannerVisible(reply);
 
   return (
-    <div className="d-flex flex-column mt-2.5 " data-testid={`reply-${reply.id}`} role="listitem">
+    <div className="d-flex flex-column mt-2.5 " data-testid={`reply-${id}`} role="listitem">
       <Confirmation
         isOpen={isDeleting}
         title={intl.formatMessage(messages.deleteCommentTitle)}
@@ -73,7 +87,7 @@ function Reply({
         closeButtonVaraint="tertiary"
         confirmButtonText={intl.formatMessage(messages.deleteConfirmationDelete)}
       />
-      {!reply.abuseFlagged && (
+      {!abuseFlagged && (
         <Confirmation
           isOpen={isReporting}
           title={intl.formatMessage(messages.reportCommentTitle)}
@@ -89,16 +103,24 @@ function Reply({
             <Avatar />
           </div>
           <div className="w-100">
-            <AlertBanner content={reply} intl={intl} />
+            <AlertBanner
+              author={author}
+              abuseFlagged={abuseFlagged}
+              closed={closed}
+              closedBy={closedBy}
+              closeReason={closeReason}
+              lastEdit={lastEdit}
+              editByLabel={editByLabel}
+              closedByLabel={closedByLabel}
+            />
           </div>
         </div>
       )}
-
       <div className="d-flex">
         <div className="d-flex mr-3 mt-2.5">
           <Avatar
             className={`ml-0.5 mt-0.5 border-0 ${colorClass ? `outline-${colorClass}` : 'outline-anonymous'}`}
-            alt={reply.author}
+            alt={author}
             style={{
               width: '32px',
               height: '32px',
@@ -111,42 +133,50 @@ function Reply({
         >
           <div className="d-flex flex-row justify-content-between" style={{ height: '24px' }}>
             <AuthorLabel
-              author={reply.author}
+              author={author}
-              authorLabel={reply.authorLabel}
+              authorLabel={authorLabel}
               labelColor={colorClass && `text-${colorClass}`}
               linkToProfile
-              postCreatedAt={reply.createdAt}
+              postCreatedAt={createdAt}
               postOrComment
             />
             <div className="ml-auto d-flex">
               <ActionsDropdown
-                commentOrPost={{
-                  ...reply,
-                  postType,
-                }}
                 actionHandlers={actionHandlers}
+                contentType={ContentTypes.COMMENT}
                 iconSize="inline"
+                id={id}
               />
             </div>
           </div>
-          {isEditing
+          {isEditing ? (
-            ? <CommentEditor comment={reply} onCloseEditor={() => setEditing(false)} />
+            <CommentEditor
-            : (
+              comment={{
-              <HTMLLoader
+                id,
-                componentId="reply"
+                threadId,
-                htmlNode={reply.renderedBody}
+                parentId,
-                cssClassName="html-loader text-break font-style text-primary-500"
+                rawBody,
-                testId={reply.id}
+                author,
-              />
+                lastEdit,
-            )}
+              }}
+              onCloseEditor={handleCloseEditor}
+            />
+          ) : (
+            <HTMLLoader
+              componentId="reply"
+              htmlNode={renderedBody}
+              cssClassName="html-loader text-break font-style text-primary-500"
+              testId={id}
+            />
+          )}
         </div>
       </div>
     </div>
   );
-}
-Reply.propTypes = {
-  postType: PropTypes.oneOf(['discussion', 'question']).isRequired,
-  reply: commentShape.isRequired,
-  intl: intlShape.isRequired,
 };
-export default injectIntl(Reply);
+
+Reply.propTypes = {
+  responseId: PropTypes.string.isRequired,
+};
+
+export default React.memo(Reply);

src/discussions/post-comments/comments/comment/ResponseEditor.jsx

@@ -1,36 +1,34 @@
-import React, { useEffect } from 'react';
+import React, { useContext, useEffect } from 'react';
 import PropTypes from 'prop-types';
 
 import classNames from 'classnames';
 
-import { injectIntl } from '@edx/frontend-platform/i18n';
+import { DiscussionContext } from '../../../common/context';
-
 import CommentEditor from './CommentEditor';
 
-function ResponseEditor({
+const ResponseEditor = ({
-  postId,
   addWrappingDiv,
   handleCloseEditor,
   addingResponse,
-}) {
+}) => {
+  const { postId } = useContext(DiscussionContext);
+
   useEffect(() => {
     handleCloseEditor();
   }, [postId]);
 
-  return addingResponse
+  return addingResponse && (
-    && (
+    <div className={classNames({ 'bg-white p-4 mb-4 rounded mt-2': addWrappingDiv })}>
-      <div className={classNames({ 'bg-white p-4 mb-4 rounded mt-2': addWrappingDiv })}>
+      <CommentEditor
-        <CommentEditor
+        comment={{ threadId: postId }}
-          comment={{ threadId: postId }}
+        edit={false}
-          edit={false}
+        onCloseEditor={handleCloseEditor}
-          onCloseEditor={handleCloseEditor}
+      />
-        />
+    </div>
-      </div>
+  );
-    );
+};
-}
 
 ResponseEditor.propTypes = {
-  postId: PropTypes.string.isRequired,
   addWrappingDiv: PropTypes.bool,
   handleCloseEditor: PropTypes.func.isRequired,
   addingResponse: PropTypes.bool.isRequired,
@@ -40,4 +38,4 @@ ResponseEditor.defaultProps = {
   addWrappingDiv: false,
 };
 
-export default injectIntl(ResponseEditor);
+export default React.memo(ResponseEditor);

src/discussions/post-comments/data/api.js

@@ -27,6 +27,7 @@ export async function getThreadComments(
     pageSize,
     reverseOrder,
     enableInContextSidebar = false,
+    signal,
   } = {},
 ) {
   const params = snakeCaseObject({
@@ -40,7 +41,7 @@ export async function getThreadComments(
   });
 
   const { data } = await getAuthenticatedHttpClient()
-    .get(getCommentsApiUrl(), { params });
+    .get(getCommentsApiUrl(), { params: { ...params, signal } });
   return data;
 }
 

src/discussions/post-comments/data/hooks.js

@@ -1,4 +1,6 @@
-import { useContext, useEffect } from 'react';
+import {
+  useCallback, useContext, useEffect, useMemo,
+} from 'react';
 
 import { useDispatch, useSelector } from 'react-redux';
 
@@ -9,20 +11,21 @@ import { useDispatchWithState } from '../../../data/hooks';
 import { DiscussionContext } from '../../common/context';
 import { selectThread } from '../../posts/data/selectors';
 import { markThreadAsRead } from '../../posts/data/thunks';
+import { filterPosts } from '../../utils';
 import {
   selectCommentSortOrder, selectThreadComments, selectThreadCurrentPage, selectThreadHasMorePages,
 } from './selectors';
 import { fetchThreadComments } from './thunks';
 
-function trackLoadMoreEvent(postId, params) {
+const trackLoadMoreEvent = (postId, params) => (
   sendTrackEvent(
     'edx.forum.responses.loadMore',
     {
       postId,
       params,
     },
-  );
+  )
-}
+);
 
 export function usePost(postId) {
   const dispatch = useDispatch();
@@ -34,18 +37,26 @@ export function usePost(postId) {
     }
   }, [postId]);
 
-  return thread;
+  return thread || {};
 }
 
-export function usePostComments(postId, endorsed = null) {
+export function usePostComments(endorsed = null) {
+  const { enableInContextSidebar, postId } = useContext(DiscussionContext);
   const [isLoading, dispatch] = useDispatchWithState();
   const comments = useSelector(selectThreadComments(postId, endorsed));
   const reverseOrder = useSelector(selectCommentSortOrder);
   const hasMorePages = useSelector(selectThreadHasMorePages(postId, endorsed));
   const currentPage = useSelector(selectThreadCurrentPage(postId, endorsed));
-  const { enableInContextSidebar } = useContext(DiscussionContext);
 
-  const handleLoadMoreResponses = async () => {
+  const endorsedCommentsIds = useMemo(() => (
+    [...filterPosts(comments, 'endorsed')].map(comment => comment.id)
+  ), [comments]);
+
+  const unEndorsedCommentsIds = useMemo(() => (
+    [...filterPosts(comments, 'unendorsed')].map(comment => comment.id)
+  ), [comments]);
+
+  const handleLoadMoreResponses = useCallback(async () => {
     const params = {
       endorsed,
       page: currentPage + 1,
@@ -53,19 +64,27 @@ export function usePostComments(postId, endorsed = null) {
     };
     await dispatch(fetchThreadComments(postId, params));
     trackLoadMoreEvent(postId, params);
-  };
+  }, [currentPage, endorsed, postId, reverseOrder]);
 
   useEffect(() => {
+    const abortController = new AbortController();
+
     dispatch(fetchThreadComments(postId, {
       endorsed,
       page: 1,
       reverseOrder,
       enableInContextSidebar,
+      signal: abortController.signal,
     }));
-  }, [postId, reverseOrder]);
+
+    return () => {
+      abortController.abort();
+    };
+  }, [postId, endorsed, reverseOrder, enableInContextSidebar]);
 
   return {
-    comments,
+    endorsedCommentsIds,
+    unEndorsedCommentsIds,
     hasMorePages,
     isLoading,
     handleLoadMoreResponses,
@@ -77,5 +96,9 @@ export function useCommentsCount(postId) {
   const endorsedQuestions = useSelector(selectThreadComments(postId, EndorsementStatus.ENDORSED));
   const unendorsedQuestions = useSelector(selectThreadComments(postId, EndorsementStatus.UNENDORSED));
 
-  return [...discussions, ...endorsedQuestions, ...unendorsedQuestions].length;
+  const commentsLength = useMemo(() => (
+    [...discussions, ...endorsedQuestions, ...unendorsedQuestions].length
+  ), [discussions, endorsedQuestions, unendorsedQuestions]);
+
+  return commentsLength;
 }

src/discussions/post-comments/data/selectors.js

@@ -4,6 +4,11 @@ import { createSelector } from '@reduxjs/toolkit';
 const selectCommentsById = state => state.comments.commentsById;
 const mapIdToComment = (ids, comments) => ids.map(id => comments[id]);
 
+export const selectCommentOrResponseById = commentOrResponseId => createSelector(
+  selectCommentsById,
+  comments => comments[commentOrResponseId],
+);
+
 export const selectThreadComments = (threadId, endorsed = null) => createSelector(
   [
     state => state.comments.commentsInThreads[threadId]?.[endorsed] || [],
@@ -12,6 +17,10 @@ export const selectThreadComments = (threadId, endorsed = null) => createSelecto
   mapIdToComment,
 );
 
+export const selectCommentResponsesIds = commentId => (
+  state => state.comments.commentsInComments[commentId] || []
+);
+
 export const selectCommentResponses = commentId => createSelector(
   [
     state => state.comments.commentsInComments[commentId] || [],

src/discussions/post-comments/data/thunks.js

@@ -81,13 +81,14 @@ export function fetchThreadComments(
     reverseOrder,
     endorsed = EndorsementStatus.DISCUSSION,
     enableInContextSidebar,
+    signal,
   } = {},
 ) {
   return async (dispatch) => {
     try {
       dispatch(fetchCommentsRequest());
       const data = await getThreadComments(threadId, {
-        page, reverseOrder, endorsed, enableInContextSidebar,
+        page, reverseOrder, endorsed, enableInContextSidebar, signal,
       });
       dispatch(fetchCommentsSuccess({
         ...normaliseComments(camelCaseObject(data)),

src/discussions/post-comments/postCommentsContext.js

@@ -0,0 +1,8 @@
+/* eslint-disable import/prefer-default-export */
+import React from 'react';
+
+export const PostCommentsContext = React.createContext({
+  isClosed: false,
+  postType: 'discussion',
+  postId: '',
+});

src/discussions/posts/NoResults.jsx

@@ -1,13 +1,16 @@
+import React from 'react';
+
 import classNames from 'classnames';
 import { useSelector } from 'react-redux';
 
-import { injectIntl, intlShape } from '@edx/frontend-platform/i18n';
+import { useIntl } from '@edx/frontend-platform/i18n';
 
 import { selectAreThreadsFiltered } from '../data/selectors';
 import { selectTopicFilter } from '../in-context-topics/data/selectors';
 import messages from '../messages';
 
-function NoResults({ intl }) {
+const NoResults = () => {
+  const intl = useIntl();
   const postsFiltered = useSelector(selectAreThreadsFiltered);
   const inContextTopicsFilter = useSelector(selectTopicFilter);
   const topicsFilter = useSelector(({ topics }) => topics.filter);
@@ -17,6 +20,7 @@ function NoResults({ intl }) {
     || (learnersFilter !== null) || (inContextTopicsFilter !== '');
 
   let helpMessage = messages.removeFilters;
+
   if (!isFiltered) {
     return null;
   } if (filters.search || learnersFilter) {
@@ -24,6 +28,7 @@ function NoResults({ intl }) {
   } if (topicsFilter || inContextTopicsFilter) {
     helpMessage = messages.removeKeywordsOnly;
   }
+
   const titleCssClasses = classNames(
     { 'font-weight-normal text-primary-500': topicsFilter || learnersFilter },
   );
@@ -37,10 +42,6 @@ function NoResults({ intl }) {
       <small className={textCssClasses}>{intl.formatMessage(helpMessage)}</small>
     </div>
   );
-}
-
-NoResults.propTypes = {
-  intl: intlShape.isRequired,
 };
 
-export default injectIntl(NoResults);
+export default NoResults;

src/discussions/posts/PostsList.jsx

@@ -5,7 +5,7 @@ import PropTypes from 'prop-types';
 
 import { useDispatch, useSelector } from 'react-redux';
 
-import { injectIntl, intlShape } from '@edx/frontend-platform/i18n';
+import { useIntl } from '@edx/frontend-platform/i18n';
 import { AppContext } from '@edx/frontend-platform/react';
 import { Button, Spinner } from '@edx/paragon';
 
@@ -14,7 +14,7 @@ import { DiscussionContext } from '../common/context';
 import { selectconfigLoadingStatus, selectUserHasModerationPrivileges, selectUserIsStaff } from '../data/selectors';
 import { fetchUserPosts } from '../learners/data/thunks';
 import messages from '../messages';
-import { filterPosts } from '../utils';
+import { usePostList } from './data/hooks';
 import {
   selectThreadFilters, selectThreadNextPage, selectThreadSorting, threadsLoadingStatus,
 } from './data/selectors';
@@ -22,25 +22,24 @@ import { fetchThreads } from './data/thunks';
 import NoResults from './NoResults';
 import { PostLink } from './post';
 
-function PostsList({
+const PostsList = ({
-  posts, topics, intl, isTopicTab, parentIsLoading,
+  postsIds, topicsIds, isTopicTab, parentIsLoading,
-}) {
+}) => {
+  const intl = useIntl();
   const dispatch = useDispatch();
-  const {
-    courseId,
-    page,
-  } = useContext(DiscussionContext);
-  const loadingStatus = useSelector(threadsLoadingStatus());
   const { authenticatedUser } = useContext(AppContext);
+  const { courseId, page } = useContext(DiscussionContext);
+  const loadingStatus = useSelector(threadsLoadingStatus());
   const orderBy = useSelector(selectThreadSorting());
   const filters = useSelector(selectThreadFilters());
   const nextPage = useSelector(selectThreadNextPage());
-  const showOwnPosts = page === 'my-posts';
   const userHasModerationPrivileges = useSelector(selectUserHasModerationPrivileges);
   const userIsStaff = useSelector(selectUserIsStaff);
   const configStatus = useSelector(selectconfigLoadingStatus);
+  const sortedPostsIds = usePostList(postsIds);
+  const showOwnPosts = page === 'my-posts';
 
-  const loadThreads = (topicIds, pageNum = undefined, isFilterChanged = false) => {
+  const loadThreads = useCallback((topicIds, pageNum = undefined, isFilterChanged = false) => {
     const params = {
       orderBy,
       filters,
@@ -50,75 +49,68 @@ function PostsList({
       topicIds,
       isFilterChanged,
     };
+
     if (showOwnPosts && filters.search === '') {
       dispatch(fetchUserPosts(courseId, params));
     } else {
       dispatch(fetchThreads(courseId, params));
     }
-  };
+  }, [courseId, orderBy, filters, showOwnPosts, authenticatedUser.username, userHasModerationPrivileges, userIsStaff]);
 
   useEffect(() => {
-    if (topics !== undefined && configStatus === RequestStatus.SUCCESSFUL) {
+    if (topicsIds !== undefined && configStatus === RequestStatus.SUCCESSFUL) {
-      loadThreads(topics);
+      loadThreads(topicsIds);
     }
-  }, [courseId, filters, orderBy, page, JSON.stringify(topics), configStatus]);
+  }, [courseId, filters, orderBy, page, JSON.stringify(topicsIds), configStatus]);
 
   useEffect(() => {
-    if (isTopicTab) { loadThreads(topics, 1, true); }
+    if (isTopicTab) {
+      loadThreads(topicsIds, 1, true);
+    }
   }, [filters]);
 
-  const checkIsSelected = (id) => window.location.pathname.includes(id);
+  const postInstances = useMemo(() => (
-  const pinnedPosts = useMemo(() => filterPosts(posts, 'pinned'), [posts]);
+    sortedPostsIds?.map((postId, idx) => (
-  const unpinnedPosts = useMemo(() => filterPosts(posts, 'unpinned'), [posts]);
-
-  const postInstances = useCallback((sortedPosts) => (
-    sortedPosts.map((post, idx) => (
       <PostLink
-        post={post}
+        postId={postId}
-        key={post.id}
-        isSelected={checkIsSelected}
         idx={idx}
-        showDivider={(sortedPosts.length - 1) !== idx}
+        key={postId}
+        showDivider={(sortedPostsIds.length - 1) !== idx}
       />
     ))
-  ), []);
+  ), [sortedPostsIds]);
 
   return (
     <>
-      {!parentIsLoading && postInstances(pinnedPosts)}
+      {!parentIsLoading && postInstances}
-      {!parentIsLoading && postInstances(unpinnedPosts)}
+      {sortedPostsIds?.length === 0 && loadingStatus === RequestStatus.SUCCESSFUL && <NoResults />}
-      {posts?.length === 0 && loadingStatus === RequestStatus.SUCCESSFUL && <NoResults />}
       {loadingStatus === RequestStatus.IN_PROGRESS || parentIsLoading ? (
         <div className="d-flex justify-content-center p-4 mx-auto my-auto">
           <Spinner animation="border" variant="primary" size="lg" />
         </div>
       ) : (
         nextPage && loadingStatus === RequestStatus.SUCCESSFUL && (
-          <Button onClick={() => loadThreads(topics, nextPage)} variant="primary" size="md">
+          <Button onClick={() => loadThreads(topicsIds, nextPage)} variant="primary" size="md">
             {intl.formatMessage(messages.loadMorePosts)}
           </Button>
         )
       )}
     </>
   );
-}
+};
 
 PostsList.propTypes = {
-  posts: PropTypes.arrayOf(PropTypes.shape({
+  postsIds: PropTypes.arrayOf(PropTypes.string),
-    pinned: PropTypes.bool.isRequired,
+  topicsIds: PropTypes.arrayOf(PropTypes.string),
-    id: PropTypes.string.isRequired,
-  })),
-  topics: PropTypes.arrayOf(PropTypes.string),
   isTopicTab: PropTypes.bool,
   parentIsLoading: PropTypes.bool,
-  intl: intlShape.isRequired,
 };
 
 PostsList.defaultProps = {
-  posts: [],
+  postsIds: [],
-  topics: undefined,
+  topicsIds: undefined,
   isTopicTab: false,
   parentIsLoading: undefined,
 };
 
-export default injectIntl(PostsList);
+export default React.memo(PostsList);

src/discussions/posts/PostsView.jsx

@@ -1,4 +1,6 @@
-import React, { useContext, useEffect } from 'react';
+import React, {
+  useCallback, useContext, useEffect, useMemo,
+} from 'react';
 import PropTypes from 'prop-types';
 
 import isEmpty from 'lodash/isEmpty';
@@ -13,39 +15,42 @@ import { fetchCourseTopicsV3 } from '../in-context-topics/data/thunks';
 import { selectTopics } from '../topics/data/selectors';
 import { fetchCourseTopics } from '../topics/data/thunks';
 import { handleKeyDown } from '../utils';
-import { selectAllThreads, selectTopicThreads } from './data/selectors';
+import { selectAllThreadsIds, selectTopicThreadsIds } from './data/selectors';
 import { setSearchQuery } from './data/slices';
 import PostFilterBar from './post-filter-bar/PostFilterBar';
 import PostsList from './PostsList';
 
-function AllPostsList() {
+const AllPostsList = () => {
-  const posts = useSelector(selectAllThreads);
+  const postsIds = useSelector(selectAllThreadsIds);
-  return <PostsList posts={posts} topics={null} />;
-}
 
-function TopicPostsList({ topicId }) {
+  return <PostsList postsIds={postsIds} topicsIds={null} />;
-  const posts = useSelector(selectTopicThreads([topicId]));
+};
-  return <PostsList posts={posts} topics={[topicId]} isTopicTab />;
+
-}
+const TopicPostsList = React.memo(({ topicId }) => {
+  const postsIds = useSelector(selectTopicThreadsIds([topicId]));
+
+  return <PostsList postsIds={postsIds} topicsIds={[topicId]} isTopicTab />;
+});
 
 TopicPostsList.propTypes = {
   topicId: PropTypes.string.isRequired,
 };
 
-function CategoryPostsList({ category }) {
+const CategoryPostsList = React.memo(({ category }) => {
   const { enableInContextSidebar } = useContext(DiscussionContext);
   const groupedCategory = useSelector(selectCurrentCategoryGrouping)(category);
   // If grouping at subsection is enabled, only apply it when browsing discussions in context in the learning MFE.
   const topicIds = useSelector(selectTopicsUnderCategory)(enableInContextSidebar ? groupedCategory : category);
-  const posts = useSelector(enableInContextSidebar ? selectAllThreads : selectTopicThreads(topicIds));
+  const postsIds = useSelector(enableInContextSidebar ? selectAllThreadsIds : selectTopicThreadsIds(topicIds));
-  return <PostsList posts={posts} topics={topicIds} />;
+
-}
+  return <PostsList postsIds={postsIds} topicsIds={topicIds} />;
+});
 
 CategoryPostsList.propTypes = {
   category: PropTypes.string.isRequired,
 };
 
-function PostsView() {
+const PostsView = () => {
   const {
     topicId,
     category,
@@ -68,15 +73,19 @@ function PostsView() {
     }
   }, [topics]);
 
-  let postsListComponent;
+  const handleOnClear = useCallback(() => {
+    dispatch(setSearchQuery(''));
+  }, []);
 
-  if (topicId) {
+  const postsListComponent = useMemo(() => {
-    postsListComponent = <TopicPostsList topicId={topicId} />;
+    if (topicId) {
-  } else if (category) {
+      return <TopicPostsList topicId={topicId} />;
-    postsListComponent = <CategoryPostsList category={category} />;
+    }
-  } else {
+    if (category) {
-    postsListComponent = <AllPostsList />;
+      return <CategoryPostsList category={category} />;
-  }
+    }
+    return <AllPostsList />;
+  }, [topicId, category]);
 
   return (
     <div className="discussion-posts d-flex flex-column h-100">
@@ -85,7 +94,7 @@ function PostsView() {
           count={resultsFound}
           text={searchString}
           loadingStatus={loadingStatus}
-          onClear={() => dispatch(setSearchQuery(''))}
+          onClear={handleOnClear}
           textSearchRewrite={textSearchRewrite}
         />
       )}
@@ -96,9 +105,6 @@ function PostsView() {
       </div>
     </div>
   );
-}
-
-PostsView.propTypes = {
 };
 
 export default PostsView;

src/discussions/posts/data/hooks.js

@@ -0,0 +1,26 @@
+/* eslint-disable import/prefer-default-export */
+import { useMemo } from 'react';
+
+import { useSelector } from 'react-redux';
+
+import { selectThreadsByIds } from './selectors';
+
+export const usePostList = (ids) => {
+  const posts = useSelector(selectThreadsByIds(ids));
+  const pinnedPostsIds = [];
+  const unpinnedPostsIds = [];
+
+  const sortedIds = useMemo(() => {
+    posts.forEach((post) => {
+      if (post.pinned) {
+        pinnedPostsIds.push(post.id);
+      } else {
+        unpinnedPostsIds.push(post.id);
+      }
+    });
+
+    return [...pinnedPostsIds, ...unpinnedPostsIds];
+  }, [posts]);
+
+  return sortedIds;
+};

src/discussions/posts/data/selectors.js

@@ -16,6 +16,15 @@ export const selectTopicThreads = topicIds => createSelector(
   mapIdsToThreads,
 );
 
+export const selectTopicThreadsIds = topicIds => state => (
+  (topicIds || []).flatMap(topicId => state.threads.threadsInTopic[topicId] || [])
+);
+
+export const selectThreadsByIds = ids => createSelector(
+  [selectThreads],
+  (threads) => mapIdsToThreads(ids, threads),
+);
+
 export const selectThread = threadId => createSelector(
   [selectThreads],
   (threads) => threads?.[threadId],
@@ -37,6 +46,11 @@ export const selectAllThreads = createSelector(
   (pages, threads) => pages.flatMap(ids => mapIdsToThreads(ids, threads)),
 );
 
+export const selectAllThreadsIds = createSelector(
+  [state => state.threads.pages],
+  pages => pages.flatMap(ids => ids),
+);
+
 export const threadsLoadingStatus = () => state => state.threads.status;
 
 export const selectThreadSorting = () => state => state.threads.sortedBy;

src/discussions/posts/data/slices.js

@@ -15,7 +15,10 @@ const mergeThreadsInTopics = (dataFromState, dataFromPayload) => {
     const values = Object.values(obj);
     keys.forEach((key, index) => {
       if (!acc[key]) { acc[key] = []; }
-      if (Array.isArray(acc[key])) { acc[key] = acc[key].concat(values[index]); } else { acc[key].push(values[index]); }
+      if (Array.isArray(acc[key])) {
+        const uniqueValues = [...new Set(acc[key].concat(values[index]))];
+        acc[key] = uniqueValues;
+      } else { acc[key].push(values[index]); }
       return acc;
     });
     return acc;
@@ -68,29 +71,29 @@ const threadsSlice = createSlice({
       state.status = RequestStatus.IN_PROGRESS;
     },
     fetchThreadsSuccess: (state, { payload }) => {
-      if (state.author !== payload.author) {
+      const {
+        author, page, ids, threadsById, isFilterChanged, threadsInTopic, avatars, pagination, textSearchRewrite,
+      } = payload;
+
+      if (state.author !== author) {
         state.pages = [];
-        state.author = payload.author;
+        state.author = author;
       }
-      if (state.pages[payload.page - 1]) {
+      if (!state.pages[page - 1]) {
-        state.pages[payload.page - 1] = [...state.pages[payload.page - 1], ...payload.ids];
+        state.pages[page - 1] = ids;
       } else {
-        state.pages[payload.page - 1] = payload.ids;
+        state.pages[page - 1] = [...new Set([...state.pages[page - 1], ...ids])];
       }
       state.status = RequestStatus.SUCCESSFUL;
-      state.threadsById = { ...state.threadsById, ...payload.threadsById };
+      state.threadsById = { ...state.threadsById, ...threadsById };
-      // filter
+      state.threadsInTopic = (isFilterChanged || page === 1)
-      if (payload.isFilterChanged) {
+        ? { ...threadsInTopic }
-        state.threadsInTopic = { ...payload.threadsInTopic };
+        : mergeThreadsInTopics(state.threadsInTopic, threadsInTopic);
-      } else {
+      state.avatars = { ...state.avatars, ...avatars };
-        state.threadsInTopic = mergeThreadsInTopics(state.threadsInTopic, payload.threadsInTopic);
+      state.nextPage = (page < pagination.numPages) ? page + 1 : null;
-      }
+      state.totalPages = pagination.numPages;
-
+      state.totalThreads = pagination.count;
-      state.avatars = { ...state.avatars, ...payload.avatars };
+      state.textSearchRewrite = textSearchRewrite;
-      state.nextPage = (payload.page < payload.pagination.numPages) ? payload.page + 1 : null;
-      state.totalPages = payload.pagination.numPages;
-      state.totalThreads = payload.pagination.count;
-      state.textSearchRewrite = payload.textSearchRewrite;
     },
     fetchThreadsFailed: (state) => {
       state.status = RequestStatus.FAILED;

src/discussions/posts/post-actions-bar/PostActionsBar.jsx

@@ -1,9 +1,9 @@
-import React, { useContext } from 'react';
+import React, { useCallback, useContext } from 'react';
 
 import classNames from 'classnames';
 import { useDispatch, useSelector } from 'react-redux';
 
-import { injectIntl, intlShape } from '@edx/frontend-platform/i18n';
+import { useIntl } from '@edx/frontend-platform/i18n';
 import {
   Button, Icon, IconButton,
 } from '@edx/paragon';
@@ -21,18 +21,21 @@ import messages from './messages';
 
 import './actionBar.scss';
 
-function PostActionsBar({
+const PostActionsBar = () => {
-  intl,
+  const intl = useIntl();
-}) {
   const dispatch = useDispatch();
   const loadingStatus = useSelector(selectconfigLoadingStatus);
   const enableInContext = useSelector(selectEnableInContext);
   const userCanAddThreadInBlackoutDate = useUserCanAddThreadInBlackoutDate();
   const { enableInContextSidebar, page } = useContext(DiscussionContext);
 
-  const handleCloseInContext = () => {
+  const handleCloseInContext = useCallback(() => {
     postMessageToParent('learning.events.sidebar.close');
-  };
+  }, []);
+
+  const handleAddPost = useCallback(() => {
+    dispatch(showPostEditor());
+  }, []);
 
   return (
     <div className={classNames('d-flex justify-content-end flex-grow-1', { 'py-1': !enableInContextSidebar })}>
@@ -53,7 +56,7 @@ function PostActionsBar({
             variant={enableInContextSidebar ? 'plain' : 'brand'}
             className={classNames('my-0 font-style border-0 line-height-24',
               { 'px-3 py-10px border-0': enableInContextSidebar })}
-            onClick={() => dispatch(showPostEditor())}
+            onClick={handleAddPost}
             size={enableInContextSidebar ? 'md' : 'sm'}
           >
             {intl.formatMessage(messages.addAPost)}
@@ -77,10 +80,6 @@ function PostActionsBar({
       )}
     </div>
   );
-}
-
-PostActionsBar.propTypes = {
-  intl: intlShape.isRequired,
 };
 
-export default injectIntl(PostActionsBar);
+export default PostActionsBar;

src/discussions/posts/post-editor/PostEditor.jsx

@@ -1,9 +1,8 @@
 import React, {
-  useContext, useEffect, useRef,
+  useCallback, useContext, useEffect, useRef,
 } from 'react';
 import PropTypes from 'prop-types';
 
-import classNames from 'classnames';
 import { Formik } from 'formik';
 import { isEmpty } from 'lodash';
 import { useDispatch, useSelector } from 'react-redux';
@@ -13,7 +12,7 @@ import * as Yup from 'yup';
 import { useIntl } from '@edx/frontend-platform/i18n';
 import { AppContext } from '@edx/frontend-platform/react';
 import {
-  Button, Card, Form, Spinner, StatefulButton,
+  Button, Form, Spinner, StatefulButton,
 } from '@edx/paragon';
 import { Help, Post } from '@edx/paragon/icons';
 
@@ -49,58 +48,22 @@ import { hidePostEditor } from '../data';
 import { selectThread } from '../data/selectors';
 import { createNewThread, fetchThread, updateExistingThread } from '../data/thunks';
 import messages from './messages';
+import PostTypeCard from './PostTypeCard';
 
-function DiscussionPostType({
+const PostEditor = ({
-  value,
-  type,
-  selected,
-  icon,
-}) {
-  const { enableInContextSidebar } = useContext(DiscussionContext);
-  // Need to use regular label since Form.Label doesn't support overriding htmlFor
-  return (
-    <label htmlFor={`post-type-${value}`} className="d-flex p-0 my-0 mr-3">
-      <Form.Radio value={value} id={`post-type-${value}`} className="sr-only">{type}</Form.Radio>
-      <Card
-        className={classNames('border-2 shadow-none', {
-          'border-primary': selected,
-          'border-light-400': !selected,
-        })}
-        style={{ cursor: 'pointer', width: `${enableInContextSidebar ? '10.021rem' : '14.25rem'}` }}
-      >
-        <Card.Section className="px-4 py-3 d-flex flex-column align-items-center">
-          <span className="text-primary-300 mb-0.5">{icon}</span>
-          <span className="text-gray-700">{type}</span>
-        </Card.Section>
-      </Card>
-    </label>
-  );
-}
-
-DiscussionPostType.propTypes = {
-  value: PropTypes.string.isRequired,
-  type: PropTypes.string.isRequired,
-  selected: PropTypes.bool.isRequired,
-  icon: PropTypes.element.isRequired,
-};
-
-function PostEditor({
   editExisting,
-}) {
+}) => {
   const intl = useIntl();
-  const { authenticatedUser } = useContext(AppContext);
-  const dispatch = useDispatch();
-  const editorRef = useRef(null);
-  const [submitting, dispatchSubmit] = useDispatchWithState();
   const history = useHistory();
   const location = useLocation();
-  const commentsPagePath = useCommentsPagePath();
+  const dispatch = useDispatch();
-  const {
+  const editorRef = useRef(null);
-    courseId,
+  const { courseId, postId } = useParams();
-    postId,
+  const { authenticatedUser } = useContext(AppContext);
-  } = useParams();
   const { category, enableInContextSidebar } = useContext(DiscussionContext);
   const topicId = useCurrentDiscussionTopic();
+  const commentsPagePath = useCommentsPagePath();
+  const [submitting, dispatchSubmit] = useDispatchWithState();
   const enableInContext = useSelector(selectEnableInContext);
   const nonCoursewareTopics = useSelector(enableInContext ? inContextNonCourseware : selectNonCoursewareTopics);
   const nonCoursewareIds = useSelector(enableInContext ? inContextCoursewareIds : selectNonCoursewareIds);
@@ -114,6 +77,7 @@ function PostEditor({
   const { reasonCodesEnabled, editReasons } = useSelector(selectModerationSettings);
   const userIsStaff = useSelector(selectUserIsStaff);
   const archivedTopics = useSelector(selectArchivedTopics);
+  const postEditorId = `post-editor-${editExisting ? postId : 'new'}`;
 
   const canDisplayEditReason = (reasonCodesEnabled && editExisting
     && (userHasModerationPrivileges || userIsGroupTa || userIsStaff)
@@ -124,7 +88,7 @@ function PostEditor({
     editReasonCode: Yup.string().required(intl.formatMessage(messages.editReasonCodeError)),
   };
 
-  const canSelectCohort = (tId) => {
+  const canSelectCohort = useCallback((tId) => {
     // If the user isn't privileged, they can't edit the cohort.
     // If the topic is being edited the cohort can't be changed.
     if (!userHasModerationPrivileges) {
@@ -135,7 +99,7 @@ function PostEditor({
     }
     const isCohorting = settings.alwaysDivideInlineDiscussions || settings.dividedInlineDiscussions.includes(tId);
     return isCohorting;
-  };
+  }, [nonCoursewareIds, settings, userHasModerationPrivileges]);
 
   const initialValues = {
     postType: post?.type || 'discussion',
@@ -145,11 +109,13 @@ function PostEditor({
     follow: isEmpty(post?.following) ? true : post?.following,
     anonymous: allowAnonymous ? false : undefined,
     anonymousToPeers: allowAnonymousToPeers ? false : undefined,
-    editReasonCode: post?.lastEdit?.reasonCode || (userIsStaff && canDisplayEditReason ? 'violates-guidelines' : undefined),
     cohort: post?.cohort || 'default',
+    editReasonCode: post?.lastEdit?.reasonCode || (
+      userIsStaff && canDisplayEditReason ? 'violates-guidelines' : undefined
+    ),
   };
 
-  const hideEditor = (resetForm) => {
+  const hideEditor = useCallback((resetForm) => {
     resetForm({ values: initialValues });
     if (editExisting) {
       const newLocation = discussionsPath(commentsPagePath, {
@@ -162,10 +128,14 @@ function PostEditor({
       history.push(newLocation);
     }
     dispatch(hidePostEditor());
-  };
+  }, [postId, topicId, post?.author, category, editExisting, commentsPagePath, location]);
+
   // null stands for no cohort restriction ("All learners" option)
-  const selectedCohort = (cohort) => (cohort === 'default' ? null : cohort);
+  const selectedCohort = useCallback((cohort) => (
-  const submitForm = async (values, { resetForm }) => {
+    cohort === 'default' ? null : cohort),
+  []);
+
+  const submitForm = useCallback(async (values, { resetForm }) => {
     if (editExisting) {
       await dispatchSubmit(updateExistingThread(postId, {
         topicId: values.topic,
@@ -195,7 +165,10 @@ function PostEditor({
       editorRef.current.plugins.autosave.removeDraft();
     }
     hideEditor(resetForm);
-  };
+  }, [
+    allowAnonymous, allowAnonymousToPeers, canSelectCohort, editExisting,
+    enableInContextSidebar, hideEditor, postId, selectedCohort, topicId,
+  ]);
 
   useEffect(() => {
     if (userHasModerationPrivileges && isEmpty(cohorts)) {
@@ -246,8 +219,6 @@ function PostEditor({
     ...editReasonCodeValidation,
   });
 
-  const postEditorId = `post-editor-${editExisting ? postId : 'new'}`;
-
   const handleInContextSelectLabel = (section, subsection) => (
     `${section.displayName} / ${subsection.displayName}` || intl.formatMessage(messages.unnamedTopics)
   );
@@ -258,66 +229,65 @@ function PostEditor({
       initialValues={initialValues}
       validationSchema={validationSchema}
       onSubmit={submitForm}
-    >{
+    >{({
-      ({
+      values,
-        values,
+      errors,
-        errors,
+      touched,
-        touched,
+      handleSubmit,
-        handleSubmit,
+      handleBlur,
-        handleBlur,
+      handleChange,
-        handleChange,
+      resetForm,
-        resetForm,
+    }) => (
-      }) => (
+      <Form className="m-4 card p-4 post-form" onSubmit={handleSubmit}>
-        <Form className="m-4 card p-4 post-form" onSubmit={handleSubmit}>
+        <h4 className="mb-4 font-style font-size-16" style={{ lineHeight: '16px' }}>
-          <h4 className="mb-4 font-style font-size-16" style={{ lineHeight: '16px' }}>
+          {editExisting
-            {editExisting
+            ? intl.formatMessage(messages.editPostHeading)
-              ? intl.formatMessage(messages.editPostHeading)
+            : intl.formatMessage(messages.addPostHeading)}
-              : intl.formatMessage(messages.addPostHeading)}
+        </h4>
-          </h4>
+        <Form.RadioSet
-          <Form.RadioSet
+          name="postType"
-            name="postType"
+          className="d-flex flex-row flex-wrap"
-            className="d-flex flex-row flex-wrap"
+          value={values.postType}
-            value={values.postType}
+          onChange={handleChange}
-            onChange={handleChange}
+          onBlur={handleBlur}
-            onBlur={handleBlur}
+          aria-label={intl.formatMessage(messages.postTitle)}
-            aria-label={intl.formatMessage(messages.postTitle)}
+        >
-          >
+          <PostTypeCard
-            <DiscussionPostType
+            value="discussion"
-              value="discussion"
+            selected={values.postType === 'discussion'}
-              selected={values.postType === 'discussion'}
+            type={intl.formatMessage(messages.discussionType)}
-              type={intl.formatMessage(messages.discussionType)}
+            icon={<Post />}
-              icon={<Post />}
+          />
-            />
+          <PostTypeCard
-            <DiscussionPostType
+            value="question"
-              value="question"
+            selected={values.postType === 'question'}
-              selected={values.postType === 'question'}
+            type={intl.formatMessage(messages.questionType)}
-              type={intl.formatMessage(messages.questionType)}
+            icon={<Help />}
-              icon={<Help />}
+          />
-            />
+        </Form.RadioSet>
-          </Form.RadioSet>
+        <div className="d-flex flex-row my-4.5 justify-content-between">
-          <div className="d-flex flex-row my-4.5 justify-content-between">
+          <Form.Group className="w-100 m-0">
-            <Form.Group className="w-100 m-0">
+            <Form.Control
-              <Form.Control
+              className="m-0"
-                className="m-0"
+              name="topic"
-                name="topic"
+              as="select"
-                as="select"
+              value={values.topic}
-                value={values.topic}
+              onChange={handleChange}
-                onChange={handleChange}
+              onBlur={handleBlur}
-                onBlur={handleBlur}
+              aria-describedby="topicAreaInput"
-                aria-describedby="topicAreaInput"
+              floatingLabel={intl.formatMessage(messages.topicArea)}
-                floatingLabel={intl.formatMessage(messages.topicArea)}
+              disabled={enableInContextSidebar}
-                disabled={enableInContextSidebar}
+            >
-              >
+              {nonCoursewareTopics.map(topic => (
-                {nonCoursewareTopics.map(topic => (
+                <option
-                  <option
+                  key={topic.id}
-                    key={topic.id}
+                  value={topic.id}
-                    value={topic.id}
+                >{topic.name || intl.formatMessage(messages.unnamedSubTopics)}
-                  >{topic.name || intl.formatMessage(messages.unnamedSubTopics)}
+                </option>
-                  </option>
+              ))}
-                ))}
+              {enableInContext ? (
-                {enableInContext ? (
+                <>
-                  <>
+                  {coursewareTopics?.map(section => (
-                    {coursewareTopics?.map(section => (
                       section?.children?.map(subsection => (
                         <optgroup
                           label={handleInContextSelectLabel(section, subsection)}
@@ -330,177 +300,172 @@ function PostEditor({
                           ))}
                         </optgroup>
                       ))
+                  ))}
+                  {(userIsStaff || userIsGroupTa || userHasModerationPrivileges) && (
+                  <optgroup label={intl.formatMessage(messages.archivedTopics)}>
+                    {archivedTopics.map(topic => (
+                      <option key={topic.id} value={topic.id}>
+                        {topic.name || intl.formatMessage(messages.unnamedSubTopics)}
+                      </option>
                     ))}
-                    {(userIsStaff || userIsGroupTa || userHasModerationPrivileges) && (
+                  </optgroup>
-                      <optgroup label={intl.formatMessage(messages.archivedTopics)}>
+                  )}
-                        {archivedTopics.map(topic => (
+                </>
-                          <option key={topic.id} value={topic.id}>
+              ) : (
-                            {topic.name || intl.formatMessage(messages.unnamedSubTopics)}
+                coursewareTopics.map(categoryObj => (
-                          </option>
+                  <optgroup
-                        ))}
+                    label={categoryObj.name || intl.formatMessage(messages.unnamedTopics)}
-                      </optgroup>
+                    key={categoryObj.id}
-                    )}
+                  >
-                  </>
+                    {categoryObj.topics.map(subtopic => (
-                ) : (
+                      <option key={subtopic.id} value={subtopic.id}>
-                  coursewareTopics.map(categoryObj => (
+                        {subtopic.name || intl.formatMessage(messages.unnamedSubTopics)}
-                    <optgroup
+                      </option>
-                      label={categoryObj.name || intl.formatMessage(messages.unnamedTopics)}
+                    ))}
-                      key={categoryObj.id}
+                  </optgroup>
-                    >
+                ))
-                      {categoryObj.topics.map(subtopic => (
+              )}
-                        <option key={subtopic.id} value={subtopic.id}>
+            </Form.Control>
-                          {subtopic.name || intl.formatMessage(messages.unnamedSubTopics)}
+          </Form.Group>
-                        </option>
+          {canSelectCohort(values.topic) && (
-                      ))}
+          <Form.Group className="w-100 ml-3 mb-0">
-                    </optgroup>
+            <Form.Control
-                  ))
+              className="m-0"
-                )}
+              name="cohort"
-              </Form.Control>
+              as="select"
-            </Form.Group>
+              value={values.cohort}
-            {canSelectCohort(values.topic) && (
+              onChange={handleChange}
-              <Form.Group className="w-100 ml-3 mb-0">
+              onBlur={handleBlur}
-                <Form.Control
+              aria-describedby="cohortAreaInput"
-                  className="m-0"
+              floatingLabel={intl.formatMessage(messages.cohortVisibility)}
-                  name="cohort"
-                  as="select"
-                  value={values.cohort}
-                  onChange={handleChange}
-                  onBlur={handleBlur}
-                  aria-describedby="cohortAreaInput"
-                  floatingLabel={intl.formatMessage(messages.cohortVisibility)}
-                >
-                  <option value="default">{intl.formatMessage(messages.cohortVisibilityAllLearners)}</option>
-                  {cohorts.map(cohort => (
-                    <option key={cohort.id} value={cohort.id}>{cohort.name}</option>
-                  ))}
-                </Form.Control>
-              </Form.Group>
-            )}
-          </div>
-
-          <div className="d-flex flex-row mb-4.5 justify-content-between">
-            <Form.Group
-              className="w-100 m-0"
-              isInvalid={isFormikFieldInvalid('title', {
-                errors,
-                touched,
-              })}
             >
-              <Form.Control
+              <option value="default">{intl.formatMessage(messages.cohortVisibilityAllLearners)}</option>
-                className="m-0"
+              {cohorts.map(cohort => (
-                name="title"
+                <option key={cohort.id} value={cohort.id}>{cohort.name}</option>
-                type="text"
+              ))}
-                onChange={handleChange}
+            </Form.Control>
-                onBlur={handleBlur}
+          </Form.Group>
-                aria-describedby="titleInput"
+          )}
-                floatingLabel={intl.formatMessage(messages.postTitle)}
+        </div>
-                value={values.title}
+        <div className="d-flex flex-row mb-4.5 justify-content-between">
-              />
+          <Form.Group
-              <FormikErrorFeedback name="title" />
+            className="w-100 m-0"
-            </Form.Group>
+            isInvalid={isFormikFieldInvalid('title', {
-            {canDisplayEditReason && (
+              errors,
-              <Form.Group
+              touched,
-                className="w-100 ml-4 mb-0"
+            })}
-                isInvalid={isFormikFieldInvalid('editReasonCode', {
+          >
-                  errors,
+            <Form.Control
-                  touched,
+              className="m-0"
-                })}
+              name="title"
-              >
+              type="text"
-                <Form.Control
+              onChange={handleChange}
-                  name="editReasonCode"
+              onBlur={handleBlur}
-                  className="m-0"
+              aria-describedby="titleInput"
-                  as="select"
+              floatingLabel={intl.formatMessage(messages.postTitle)}
-                  value={values.editReasonCode}
+              value={values.title}
-                  onChange={handleChange}
+            />
-                  onBlur={handleBlur}
+            <FormikErrorFeedback name="title" />
-                  aria-describedby="editReasonCodeInput"
+          </Form.Group>
-                  floatingLabel={intl.formatMessage(messages.editReasonCode)}
+          {canDisplayEditReason && (
-                >
+          <Form.Group
-                  <option key="empty" value="">---</option>
+            className="w-100 ml-4 mb-0"
-                  {editReasons.map(({ code, label }) => (
+            isInvalid={isFormikFieldInvalid('editReasonCode', {
-                    <option key={code} value={code}>{label}</option>
+              errors,
-                  ))}
+              touched,
-                </Form.Control>
+            })}
-                <FormikErrorFeedback name="editReasonCode" />
+          >
-              </Form.Group>
+            <Form.Control
-            )}
+              name="editReasonCode"
-          </div>
+              className="m-0"
-          <div className="mb-3">
+              as="select"
-            <TinyMCEEditor
+              value={values.editReasonCode}
-              onInit={
+              onChange={handleChange}
+              onBlur={handleBlur}
+              aria-describedby="editReasonCodeInput"
+              floatingLabel={intl.formatMessage(messages.editReasonCode)}
+            >
+              <option key="empty" value="">---</option>
+              {editReasons.map(({ code, label }) => (
+                <option key={code} value={code}>{label}</option>
+              ))}
+            </Form.Control>
+            <FormikErrorFeedback name="editReasonCode" />
+          </Form.Group>
+          )}
+        </div>
+        <div className="mb-3">
+          <TinyMCEEditor
+            onInit={
                 /* istanbul ignore next: TinyMCE is mocked so this cannot be easily tested */
                 (_, editor) => {
                   editorRef.current = editor;
                 }
               }
-              id={postEditorId}
+            id={postEditorId}
-              value={values.comment}
+            value={values.comment}
-              onEditorChange={formikCompatibleHandler(handleChange, 'comment')}
+            onEditorChange={formikCompatibleHandler(handleChange, 'comment')}
-              onBlur={formikCompatibleHandler(handleBlur, 'comment')}
+            onBlur={formikCompatibleHandler(handleBlur, 'comment')}
-            />
+          />
-            <FormikErrorFeedback name="comment" />
+          <FormikErrorFeedback name="comment" />
-          </div>
+        </div>
-
+        <PostPreviewPanel htmlNode={values.comment} isPost editExisting={editExisting} />
-          <PostPreviewPanel htmlNode={values.comment} isPost editExisting={editExisting} />
+        <div className="d-flex flex-row mt-n4 w-75 text-primary font-style">
-
+          {!editExisting && (
-          <div className="d-flex flex-row mt-n4 w-75 text-primary font-style">
+          <>
-            {!editExisting && (
+            <Form.Group>
-              <>
+              <Form.Checkbox
-                <Form.Group>
+                name="follow"
-                  <Form.Checkbox
+                checked={values.follow}
-                    name="follow"
+                onChange={handleChange}
-                    checked={values.follow}
+                onBlur={handleBlur}
-                    onChange={handleChange}
+                className="mr-4.5"
-                    onBlur={handleBlur}
+              >
-                    className="mr-4.5"
+                <span className="font-size-14">
-                  >
+                  {intl.formatMessage(messages.followPost)}
-                    <span className="font-size-14">
+                </span>
-                      {intl.formatMessage(messages.followPost)}
+              </Form.Checkbox>
-                    </span>
+            </Form.Group>
-                  </Form.Checkbox>
+            {allowAnonymousToPeers && (
-                </Form.Group>
+            <Form.Group>
-                {allowAnonymousToPeers && (
+              <Form.Checkbox
-                  <Form.Group>
+                name="anonymousToPeers"
-                    <Form.Checkbox
+                checked={values.anonymousToPeers}
-                      name="anonymousToPeers"
+                onChange={handleChange}
-                      checked={values.anonymousToPeers}
+                onBlur={handleBlur}
-                      onChange={handleChange}
+              >
-                      onBlur={handleBlur}
+                <span className="font-size-14">
-                    >
+                  {intl.formatMessage(messages.anonymousToPeersPost)}
-                      <span className="font-size-14">
+                </span>
-                        {intl.formatMessage(messages.anonymousToPeersPost)}
+              </Form.Checkbox>
-                      </span>
+            </Form.Group>
-                    </Form.Checkbox>
-                  </Form.Group>
-                )}
-              </>
             )}
-          </div>
+          </>
-
+          )}
-          <div className="d-flex justify-content-end">
+        </div>
-            <Button
+        <div className="d-flex justify-content-end">
-              variant="outline-primary"
+          <Button
-              onClick={() => hideEditor(resetForm)}
+            variant="outline-primary"
-            >
+            onClick={() => hideEditor(resetForm)}
-              {intl.formatMessage(messages.cancel)}
+          >
-            </Button>
+            {intl.formatMessage(messages.cancel)}
-            <StatefulButton
+          </Button>
-              labels={{
+          <StatefulButton
-                default: intl.formatMessage(messages.submit),
+            labels={{
-                pending: intl.formatMessage(messages.submitting),
+              default: intl.formatMessage(messages.submit),
-              }}
+              pending: intl.formatMessage(messages.submitting),
-              state={submitting ? 'pending' : 'default'}
+            }}
-              className="ml-2"
+            state={submitting ? 'pending' : 'default'}
-              variant="primary"
+            className="ml-2"
-              onClick={handleSubmit}
+            variant="primary"
-            />
+            onClick={handleSubmit}
-          </div>
+          />
-        </Form>
+        </div>
-      )
+      </Form>
-      }
+    )}
     </Formik>
   );
-}
+};
 
 PostEditor.propTypes = {
   editExisting: PropTypes.bool,
@@ -510,4 +475,4 @@ PostEditor.defaultProps = {
   editExisting: false,
 };
 
-export default PostEditor;
+export default React.memo(PostEditor);

src/discussions/posts/post-editor/PostTypeCard.jsx

@@ -0,0 +1,44 @@
+import React, { useContext } from 'react';
+import PropTypes from 'prop-types';
+
+import classNames from 'classnames';
+
+import { Card, Form } from '@edx/paragon';
+
+import { DiscussionContext } from '../../common/context';
+
+const PostTypeCard = ({
+  value,
+  type,
+  selected,
+  icon,
+}) => {
+  const { enableInContextSidebar } = useContext(DiscussionContext);
+  // Need to use regular label since Form.Label doesn't support overriding htmlFor
+  return (
+    <label htmlFor={`post-type-${value}`} className="d-flex p-0 my-0 mr-3">
+      <Form.Radio value={value} id={`post-type-${value}`} className="sr-only">{type}</Form.Radio>
+      <Card
+        className={classNames('border-2 shadow-none', {
+          'border-primary': selected,
+          'border-light-400': !selected,
+        })}
+        style={{ cursor: 'pointer', width: `${enableInContextSidebar ? '10.021rem' : '14.25rem'}` }}
+      >
+        <Card.Section className="px-4 py-3 d-flex flex-column align-items-center">
+          <span className="text-primary-300 mb-0.5">{icon}</span>
+          <span className="text-gray-700">{type}</span>
+        </Card.Section>
+      </Card>
+    </label>
+  );
+};
+
+PostTypeCard.propTypes = {
+  value: PropTypes.string.isRequired,
+  type: PropTypes.string.isRequired,
+  selected: PropTypes.bool.isRequired,
+  icon: PropTypes.element.isRequired,
+};
+
+export default React.memo(PostTypeCard);

src/discussions/posts/post-filter-bar/PostFilterBar.jsx

@@ -1,5 +1,5 @@
 import React, {
-  useContext, useEffect, useMemo, useState,
+  useCallback, useContext, useEffect, useMemo, useState,
 } from 'react';
 import PropTypes from 'prop-types';
 
@@ -9,7 +9,7 @@ import { useDispatch, useSelector } from 'react-redux';
 import { useParams } from 'react-router-dom';
 
 import { sendTrackEvent } from '@edx/frontend-platform/analytics';
-import { injectIntl, intlShape } from '@edx/frontend-platform/i18n';
+import { useIntl } from '@edx/frontend-platform/i18n';
 import {
   Collapsible, Form, Icon, Spinner,
 } from '@edx/paragon';
@@ -29,7 +29,7 @@ import {
 import { selectThreadFilters, selectThreadSorting } from '../data/selectors';
 import messages from './messages';
 
-export const ActionItem = ({
+export const ActionItem = React.memo(({
   id,
   label,
   value,
@@ -52,7 +52,7 @@ export const ActionItem = ({
       {label}
     </span>
   </label>
-);
+));
 
 ActionItem.propTypes = {
   id: PropTypes.string.isRequired,
@@ -61,9 +61,8 @@ ActionItem.propTypes = {
   selected: PropTypes.string.isRequired,
 };
 
-function PostFilterBar({
+const PostFilterBar = () => {
-  intl,
+  const intl = useIntl();
-}) {
   const dispatch = useDispatch();
   const { courseId } = useParams();
   const { page } = useContext(DiscussionContext);
@@ -75,11 +74,13 @@ function PostFilterBar({
   const cohorts = useSelector(selectCourseCohorts);
   const [isOpen, setOpen] = useState(false);
 
-  const selectedCohort = useMemo(() => cohorts.find(cohort => (
+  const selectedCohort = useMemo(() => (
-    toString(cohort.id) === currentFilters.cohort)),
+    cohorts.find(cohort => (
-  [currentFilters.cohort]);
+      toString(cohort.id) === currentFilters.cohort
+    ))
+  ), [cohorts, currentFilters.cohort]);
 
-  const handleSortFilterChange = (event) => {
+  const handleSortFilterChange = useCallback((event) => {
     const currentType = currentFilters.postType;
     const currentStatus = currentFilters.status;
     const {
@@ -93,6 +94,7 @@ function PostFilterBar({
       cohortFilter: selectedCohort,
       triggeredBy: name,
     };
+
     if (name === 'type') {
       dispatch(setPostsTypeFilter(value));
       if (
@@ -103,6 +105,7 @@ function PostFilterBar({
       }
       filterContentEventProperties.threadTypeFilter = value;
     }
+
     if (name === 'status') {
       dispatch(setStatusFilter(value));
       if (value === PostsStatusFilter.UNANSWERED && currentType !== ThreadType.QUESTION) {
@@ -115,16 +118,23 @@ function PostFilterBar({
       }
       filterContentEventProperties.statusFilter = value;
     }
+
     if (name === 'sort') {
       dispatch(setSortedBy(value));
       filterContentEventProperties.sortFilter = value;
     }
+
     if (name === 'cohort') {
       dispatch(setCohortFilter(value));
       filterContentEventProperties.cohortFilter = value;
     }
+
     sendTrackEvent('edx.forum.filter.content', filterContentEventProperties);
-  };
+  }, [currentFilters, currentSorting, dispatch, selectedCohort]);
+
+  const handleToggle = useCallback(() => {
+    setOpen(!isOpen);
+  }, [isOpen]);
 
   useEffect(() => {
     if (userHasModerationPrivileges && isEmpty(cohorts)) {
@@ -132,10 +142,48 @@ function PostFilterBar({
     }
   }, [courseId, userHasModerationPrivileges]);
 
+  const renderCohortFilter = useMemo(() => (
+    userHasModerationPrivileges && (
+      <>
+        <div className="border-bottom my-2" />
+        {status === RequestStatus.IN_PROGRESS ? (
+          <div className="d-flex justify-content-center p-4">
+            <Spinner animation="border" variant="primary" size="lg" />
+          </div>
+        ) : (
+          <div className="d-flex flex-row pt-2">
+            <Form.RadioSet
+              name="cohort"
+              className="d-flex flex-column list-group list-group-flush w-100"
+              value={currentFilters.cohort}
+              onChange={handleSortFilterChange}
+            >
+              <ActionItem
+                id="all-groups"
+                label="All groups"
+                value=""
+                selected={currentFilters.cohort}
+              />
+              {cohorts.map(cohort => (
+                <ActionItem
+                  key={cohort.id}
+                  id={toString(cohort.id)}
+                  label={capitalize(cohort.name)}
+                  value={toString(cohort.id)}
+                  selected={currentFilters.cohort}
+                />
+              ))}
+            </Form.RadioSet>
+          </div>
+        )}
+      </>
+    )
+  ), [cohorts, currentFilters.cohort, handleSortFilterChange, status, userHasModerationPrivileges]);
+
   return (
     <Collapsible.Advanced
       open={isOpen}
-      onToggle={() => setOpen(!isOpen)}
+      onToggle={handleToggle}
       className="filter-bar collapsible-card-lg border-0"
     >
       <Collapsible.Trigger className="collapsible-trigger border-0">
@@ -157,7 +205,6 @@ function PostFilterBar({
             <Icon src={Tune} />
           </Collapsible.Visible>
         </span>
-
       </Collapsible.Trigger>
       <Collapsible.Body className="collapsible-body px-4 pb-3 pt-0">
         <Form>
@@ -260,49 +307,11 @@ function PostFilterBar({
               />
             </Form.RadioSet>
           </div>
-          {userHasModerationPrivileges && (
+          {renderCohortFilter}
-            <>
-              <div className="border-bottom my-2" />
-              {status === RequestStatus.IN_PROGRESS ? (
-                <div className="d-flex justify-content-center p-4">
-                  <Spinner animation="border" variant="primary" size="lg" />
-                </div>
-              ) : (
-                <div className="d-flex flex-row pt-2">
-                  <Form.RadioSet
-                    name="cohort"
-                    className="d-flex flex-column list-group list-group-flush w-100"
-                    value={currentFilters.cohort}
-                    onChange={handleSortFilterChange}
-                  >
-                    <ActionItem
-                      id="all-groups"
-                      label="All groups"
-                      value=""
-                      selected={currentFilters.cohort}
-                    />
-                    {cohorts.map(cohort => (
-                      <ActionItem
-                        key={cohort.id}
-                        id={cohort.id}
-                        label={capitalize(cohort.name)}
-                        value={toString(cohort.id)}
-                        selected={currentFilters.cohort}
-                      />
-                    ))}
-                  </Form.RadioSet>
-                </div>
-              )}
-            </>
-          )}
         </Form>
       </Collapsible.Body>
     </Collapsible.Advanced>
   );
-}
-
-PostFilterBar.propTypes = {
-  intl: intlShape.isRequired,
 };
 
-export default injectIntl(PostFilterBar);
+export default React.memo(PostFilterBar);

src/discussions/posts/post/ClosePostReasonModal.jsx

@@ -1,9 +1,11 @@
-import React, { useEffect, useRef, useState } from 'react';
+import React, {
+  useCallback, useEffect, useRef, useState,
+} from 'react';
 import PropTypes from 'prop-types';
 
 import { useSelector } from 'react-redux';
 
-import { injectIntl, intlShape } from '@edx/frontend-platform/i18n';
+import { useIntl } from '@edx/frontend-platform/i18n';
 import {
   ActionRow,
   Button,
@@ -14,24 +16,23 @@ import {
 import { selectModerationSettings } from '../../data/selectors';
 import messages from './messages';
 
-function ClosePostReasonModal({
+const ClosePostReasonModal = ({
-  intl,
   isOpen,
   onCancel,
   onConfirm,
-}) {
+}) => {
+  const intl = useIntl();
   const scrollTo = useRef(null);
   const [reasonCode, setReasonCode] = useState(null);
-
   const { postCloseReasons } = useSelector(selectModerationSettings);
 
-  const onChange = event => {
+  const onChange = useCallback(event => {
     if (event.target.value) {
       setReasonCode(event.target.value);
     } else {
       setReasonCode(null);
     }
-  };
+  }, []);
 
   useEffect(() => {
     /* istanbul ignore if: This API is not available in the test environment. */
@@ -87,13 +88,12 @@ function ClosePostReasonModal({
       </ModalDialog.Footer>
     </ModalDialog>
   );
-}
+};
 
 ClosePostReasonModal.propTypes = {
-  intl: intlShape.isRequired,
   isOpen: PropTypes.bool.isRequired,
   onCancel: PropTypes.func.isRequired,
   onConfirm: PropTypes.func.isRequired,
 };
 
-export default injectIntl(ClosePostReasonModal);
+export default React.memo(ClosePostReasonModal);

src/discussions/posts/post/LikeButton.jsx

@@ -1,7 +1,7 @@
-import React from 'react';
+import React, { useCallback } from 'react';
 import PropTypes from 'prop-types';
 
-import { injectIntl, intlShape } from '@edx/frontend-platform/i18n';
+import { useIntl } from '@edx/frontend-platform/i18n';
 import {
   Icon, IconButton, OverlayTrigger, Tooltip,
 } from '@edx/paragon';
@@ -9,19 +9,16 @@ import {
 import { ThumbUpFilled, ThumbUpOutline } from '../../../components/icons';
 import messages from './messages';
 
-function LikeButton({
+const LikeButton = ({ count, onClick, voted }) => {
-  count,
+  const intl = useIntl();
-  intl,
+
-  onClick,
+  const handleClick = useCallback((e) => {
-  voted,
-}) {
-  const handleClick = (e) => {
     e.preventDefault();
     if (onClick) {
       onClick();
     }
     return false;
-  };
+  }, []);
 
   return (
     <div className="d-flex align-items-center mr-36px text-primary-500">
@@ -47,11 +44,10 @@ function LikeButton({
 
     </div>
   );
-}
+};
 
 LikeButton.propTypes = {
   count: PropTypes.number.isRequired,
-  intl: intlShape.isRequired,
   onClick: PropTypes.func,
   voted: PropTypes.bool,
 };
@@ -61,4 +57,4 @@ LikeButton.defaultProps = {
   onClick: undefined,
 };
 
-export default injectIntl(LikeButton);
+export default React.memo(LikeButton);

src/discussions/posts/post/Post.jsx

@@ -2,11 +2,12 @@ import React, { useCallback, useContext, useMemo } from 'react';
 import PropTypes from 'prop-types';
 
 import classNames from 'classnames';
+import { toString } from 'lodash';
 import { useDispatch, useSelector } from 'react-redux';
 import { useHistory, useLocation } from 'react-router-dom';
 
 import { getConfig } from '@edx/frontend-platform';
-import { injectIntl, intlShape } from '@edx/frontend-platform/i18n';
+import { useIntl } from '@edx/frontend-platform/i18n';
 import { Hyperlink, useToggle } from '@edx/paragon';
 
 import HTMLLoader from '../../../components/HTMLLoader';
@@ -15,102 +16,119 @@ import { selectorForUnitSubsection, selectTopicContext } from '../../../data/sel
 import { AlertBanner, Confirmation } from '../../common';
 import { DiscussionContext } from '../../common/context';
 import HoverCard from '../../common/HoverCard';
+import { ContentTypes } from '../../data/constants';
 import { selectModerationSettings, selectUserHasModerationPrivileges } from '../../data/selectors';
 import { selectTopic } from '../../topics/data/selectors';
+import { selectThread } from '../data/selectors';
 import { removeThread, updateExistingThread } from '../data/thunks';
 import ClosePostReasonModal from './ClosePostReasonModal';
 import messages from './messages';
 import PostFooter from './PostFooter';
 import PostHeader from './PostHeader';
-import { postShape } from './proptypes';
 
-function Post({
+const Post = ({ handleAddResponseButton }) => {
-  post,
+  const { enableInContextSidebar, postId } = useContext(DiscussionContext);
-  intl,
+  const {
-  handleAddResponseButton,
+    topicId, abuseFlagged, closed, pinned, voted, hasEndorsed, following, closedBy, voteCount, groupId, groupName,
-}) {
+    closeReason, authorLabel, type: postType, author, title, createdAt, renderedBody, lastEdit, editByLabel,
+    closedByLabel,
+  } = useSelector(selectThread(postId));
+  const intl = useIntl();
   const location = useLocation();
   const history = useHistory();
   const dispatch = useDispatch();
-  const { enableInContextSidebar } = useContext(DiscussionContext);
   const courseId = useSelector((state) => state.config.id);
-  const topic = useSelector(selectTopic(post.topicId));
+  const topic = useSelector(selectTopic(topicId));
   const getTopicSubsection = useSelector(selectorForUnitSubsection);
-  const topicContext = useSelector(selectTopicContext(post.topicId));
+  const topicContext = useSelector(selectTopicContext(topicId));
   const { reasonCodesEnabled } = useSelector(selectModerationSettings);
   const [isDeleting, showDeleteConfirmation, hideDeleteConfirmation] = useToggle(false);
   const [isReporting, showReportConfirmation, hideReportConfirmation] = useToggle(false);
   const [isClosing, showClosePostModal, hideClosePostModal] = useToggle(false);
   const userHasModerationPrivileges = useSelector(selectUserHasModerationPrivileges);
-  const displayPostFooter = post.following || post.voteCount || post.closed
+  const displayPostFooter = following || voteCount || closed || (groupId && userHasModerationPrivileges);
-  || (post.groupId && userHasModerationPrivileges);
 
-  const handleAbusedFlag = useCallback(() => {
+  const handleDeleteConfirmation = useCallback(async () => {
-    if (post.abuseFlagged) {
+    await dispatch(removeThread(postId));
-      dispatch(updateExistingThread(post.id, { flagged: !post.abuseFlagged }));
-    } else {
-      showReportConfirmation();
-    }
-  }, [dispatch, post.abuseFlagged, post.id, showReportConfirmation]);
-
-  const handleDeleteConfirmation = async () => {
-    await dispatch(removeThread(post.id));
     history.push({
       pathname: '.',
       search: enableInContextSidebar && '?inContextSidebar',
     });
     hideDeleteConfirmation();
-  };
+  }, [enableInContextSidebar, postId, hideDeleteConfirmation]);
 
-  const handleReportConfirmation = () => {
+  const handleReportConfirmation = useCallback(() => {
-    dispatch(updateExistingThread(post.id, { flagged: !post.abuseFlagged }));
+    dispatch(updateExistingThread(postId, { flagged: !abuseFlagged }));
     hideReportConfirmation();
-  };
+  }, [abuseFlagged, postId, hideReportConfirmation]);
+
+  const handlePostContentEdit = useCallback(() => history.push({
+    ...location,
+    pathname: `${location.pathname}/edit`,
+  }), [location.pathname]);
+
+  const handlePostClose = useCallback(() => {
+    if (closed) {
+      dispatch(updateExistingThread(postId, { closed: false }));
+    } else if (reasonCodesEnabled) {
+      showClosePostModal();
+    } else {
+      dispatch(updateExistingThread(postId, { closed: true }));
+    }
+  }, [closed, postId, reasonCodesEnabled, showClosePostModal]);
+
+  const handlePostCopyLink = useCallback(() => navigator.clipboard.writeText(
+    `${window.location.origin}/${courseId}/posts/${postId}`,
+  ), [window.location.origin, postId, courseId]);
+
+  const handlePostPin = useCallback(() => dispatch(updateExistingThread(
+    postId, { pinned: !pinned },
+  )), [postId, pinned]);
+
+  const handlePostReport = useCallback(() => {
+    if (abuseFlagged) {
+      dispatch(updateExistingThread(postId, { flagged: !abuseFlagged }));
+    } else {
+      showReportConfirmation();
+    }
+  }, [abuseFlagged, postId, showReportConfirmation]);
 
   const actionHandlers = useMemo(() => ({
-    [ContentActions.EDIT_CONTENT]: () => history.push({
+    [ContentActions.EDIT_CONTENT]: handlePostContentEdit,
-      ...location,
-      pathname: `${location.pathname}/edit`,
-    }),
     [ContentActions.DELETE]: showDeleteConfirmation,
-    [ContentActions.CLOSE]: () => {
+    [ContentActions.CLOSE]: handlePostClose,
-      if (post.closed) {
+    [ContentActions.COPY_LINK]: handlePostCopyLink,
-        dispatch(updateExistingThread(post.id, { closed: false }));
+    [ContentActions.PIN]: handlePostPin,
-      } else if (reasonCodesEnabled) {
+    [ContentActions.REPORT]: handlePostReport,
-        showClosePostModal();
-      } else {
-        dispatch(updateExistingThread(post.id, { closed: true }));
-      }
-    },
-    [ContentActions.COPY_LINK]: () => { navigator.clipboard.writeText(`${window.location.origin}/${courseId}/posts/${post.id}`); },
-    [ContentActions.PIN]: () => dispatch(updateExistingThread(post.id, { pinned: !post.pinned })),
-    [ContentActions.REPORT]: () => handleAbusedFlag(),
   }), [
-    showDeleteConfirmation,
+    handlePostClose, handlePostContentEdit, handlePostCopyLink, handlePostPin, handlePostReport, showDeleteConfirmation,
-    history,
-    location,
-    post.closed,
-    post.id,
-    post.pinned,
-    reasonCodesEnabled,
-    dispatch,
-    showClosePostModal,
-    courseId,
-    handleAbusedFlag,
   ]);
 
-  const getTopicCategoryName = topicData => (
+  const handleClosePostConfirmation = useCallback((closeReasonCode) => {
-    topicData.usageKey ? getTopicSubsection(topicData.usageKey)?.displayName : topicData.categoryId
+    dispatch(updateExistingThread(postId, { closed: true, closeReasonCode }));
-  );
+    hideClosePostModal();
+  }, [postId, hideClosePostModal]);
 
-  const getTopicInfo = topicData => (
+  const handlePostLike = useCallback(() => {
+    dispatch(updateExistingThread(postId, { voted: !voted }));
+  }, [postId, voted]);
+
+  const handlePostFollow = useCallback(() => {
+    dispatch(updateExistingThread(postId, { following: !following }));
+  }, [postId, following]);
+
+  const getTopicCategoryName = useCallback(topicData => (
+    topicData.usageKey ? getTopicSubsection(topicData.usageKey)?.displayName : topicData.categoryId
+  ), [getTopicSubsection]);
+
+  const getTopicInfo = useCallback(topicData => (
     getTopicCategoryName(topicData) ? `${getTopicCategoryName(topicData)} / ${topicData.name}` : `${topicData.name}`
-  );
+  ), [getTopicCategoryName]);
 
   return (
     <div
       className="d-flex flex-column w-100 mw-100 post-card-comment"
-      data-testid={`post-${post.id}`}
+      data-testid={`post-${postId}`}
       // eslint-disable-next-line jsx-a11y/no-noninteractive-tabindex
       tabIndex="0"
     >
@@ -123,7 +141,7 @@ function Post({
         closeButtonVaraint="tertiary"
         confirmButtonText={intl.formatMessage(messages.deleteConfirmationDelete)}
       />
-      {!post.abuseFlagged && (
+      {!abuseFlagged && (
         <Confirmation
           isOpen={isReporting}
           title={intl.formatMessage(messages.reportPostTitle)}
@@ -134,18 +152,39 @@ function Post({
         />
       )}
       <HoverCard
-        commentOrPost={post}
+        id={postId}
+        contentType={ContentTypes.POST}
         actionHandlers={actionHandlers}
         handleResponseCommentButton={handleAddResponseButton}
         addResponseCommentButtonMessage={intl.formatMessage(messages.addResponse)}
-        onLike={() => dispatch(updateExistingThread(post.id, { voted: !post.voted }))}
+        onLike={handlePostLike}
-        onFollow={() => dispatch(updateExistingThread(post.id, { following: !post.following }))}
+        onFollow={handlePostFollow}
-        isClosedPost={post.closed}
+        voted={voted}
+        following={following}
+      />
+      <AlertBanner
+        author={author}
+        abuseFlagged={abuseFlagged}
+        lastEdit={lastEdit}
+        closed={closed}
+        closedBy={closedBy}
+        closeReason={closeReason}
+        editByLabel={editByLabel}
+        closedByLabel={closedByLabel}
+      />
+      <PostHeader
+        abuseFlagged={abuseFlagged}
+        author={author}
+        authorLabel={authorLabel}
+        closed={closed}
+        createdAt={createdAt}
+        hasEndorsed={hasEndorsed}
+        lastEdit={lastEdit}
+        postType={postType}
+        title={title}
       />
-      <AlertBanner content={post} />
-      <PostHeader post={post} />
       <div className="d-flex mt-14px text-break font-style text-primary-500">
-        <HTMLLoader htmlNode={post.renderedBody} componentId="post" cssClassName="html-loader" testId={post.id} />
+        <HTMLLoader htmlNode={renderedBody} componentId="post" cssClassName="html-loader" testId={postId} />
       </div>
       {(topicContext || topic) && (
         <div
@@ -153,42 +192,54 @@ function Post({
             { 'w-100': enableInContextSidebar, 'mb-1': !displayPostFooter })}
           style={{ lineHeight: '20px' }}
         >
-          <span className="text-gray-500" style={{ lineHeight: '20px' }}>{intl.formatMessage(messages.relatedTo)}{' '}</span>
+          <span className="text-gray-500" style={{ lineHeight: '20px' }}>
+            {intl.formatMessage(messages.relatedTo)}{' '}
+          </span>
           <Hyperlink
-            destination={topicContext ? topicContext.unitLink : `${getConfig().BASE_URL}/${courseId}/topics/${post.topicId}`}
             target="_top"
+            destination={topicContext ? (
+              topicContext.unitLink
+            ) : (
+              `${getConfig().BASE_URL}/${courseId}/topics/${topicId}`
+            )}
           >
-            {(topicContext && !topic)
+            {(topicContext && !topic) ? (
-              ? (
+              <>
-                <>
+                <span className="w-auto">{topicContext.chapterName}</span>
-                  <span className="w-auto">{topicContext.chapterName}</span>
+                <span className="mx-1">/</span>
-                  <span className="mx-1">/</span>
+                <span className="w-auto">{topicContext.verticalName}</span>
-                  <span className="w-auto">{topicContext.verticalName}</span>
+                <span className="mx-1">/</span>
-                  <span className="mx-1">/</span>
+                <span className="w-auto">{topicContext.unitName}</span>
-                  <span className="w-auto">{topicContext.unitName}</span>
+              </>
-                </>
+            ) : (
-              )
+              getTopicInfo(topic)
-              : getTopicInfo(topic)}
+            )}
           </Hyperlink>
         </div>
       )}
-      {displayPostFooter && <PostFooter post={post} userHasModerationPrivileges={userHasModerationPrivileges} />}
+      {displayPostFooter && (
+        <PostFooter
+          id={postId}
+          voteCount={voteCount}
+          voted={voted}
+          following={following}
+          groupId={toString(groupId)}
+          groupName={groupName}
+          closed={closed}
+          userHasModerationPrivileges={userHasModerationPrivileges}
+        />
+      )}
       <ClosePostReasonModal
         isOpen={isClosing}
         onCancel={hideClosePostModal}
-        onConfirm={closeReasonCode => {
+        onConfirm={handleClosePostConfirmation}
-          dispatch(updateExistingThread(post.id, { closed: true, closeReasonCode }));
-          hideClosePostModal();
-        }}
       />
     </div>
   );
-}
+};
 
 Post.propTypes = {
-  intl: intlShape.isRequired,
-  post: postShape.isRequired,
   handleAddResponseButton: PropTypes.func.isRequired,
 };
 
-export default injectIntl(Post);
+export default React.memo(Post);

src/discussions/posts/post/PostFooter.jsx

@@ -1,9 +1,9 @@
-import React from 'react';
+import React, { useCallback } from 'react';
 import PropTypes from 'prop-types';
 
 import { useDispatch } from 'react-redux';
 
-import { injectIntl, intlShape } from '@edx/frontend-platform/i18n';
+import { useIntl } from '@edx/frontend-platform/i18n';
 import {
   Icon, IconButton, OverlayTrigger, Tooltip,
 } from '@edx/paragon';
@@ -13,36 +13,46 @@ import { StarFilled, StarOutline } from '../../../components/icons';
 import { updateExistingThread } from '../data/thunks';
 import LikeButton from './LikeButton';
 import messages from './messages';
-import { postShape } from './proptypes';
 
-function PostFooter({
+const PostFooter = ({
-  intl,
+  closed,
-  post,
+  following,
+  groupId,
+  groupName,
+  id,
   userHasModerationPrivileges,
-}) {
+  voted,
+  voteCount,
+}) => {
   const dispatch = useDispatch();
+  const intl = useIntl();
+
+  const handlePostLike = useCallback(() => {
+    dispatch(updateExistingThread(id, { voted: !voted }));
+  }, [id, voted]);
+
   return (
     <div className="d-flex align-items-center ml-n1.5 mt-10px" style={{ height: '32px' }} data-testid="post-footer">
-      {post.voteCount !== 0 && (
+      {voteCount !== 0 && (
         <LikeButton
-          count={post.voteCount}
+          count={voteCount}
-          onClick={() => dispatch(updateExistingThread(post.id, { voted: !post.voted }))}
+          onClick={handlePostLike}
-          voted={post.voted}
+          voted={voted}
         />
       )}
-      {post.following && (
+      {following && (
         <OverlayTrigger
           overlay={(
-            <Tooltip id={`follow-${post.id}-tooltip`}>
+            <Tooltip id={`follow-${id}-tooltip`}>
-              {intl.formatMessage(post.following ? messages.unFollow : messages.follow)}
+              {intl.formatMessage(following ? messages.unFollow : messages.follow)}
             </Tooltip>
           )}
         >
           <IconButton
-            src={post.following ? StarFilled : StarOutline}
+            src={following ? StarFilled : StarOutline}
             onClick={(e) => {
               e.preventDefault();
-              dispatch(updateExistingThread(post.id, { following: !post.following }));
+              dispatch(updateExistingThread(id, { following: !following }));
               return true;
             }}
             iconAs={Icon}
@@ -53,10 +63,10 @@ function PostFooter({
         </OverlayTrigger>
       )}
       <div className="d-flex flex-fill justify-content-end align-items-center">
-        {post.groupId && userHasModerationPrivileges && (
+        {groupId && userHasModerationPrivileges && (
           <OverlayTrigger
             overlay={(
-              <Tooltip id={`visibility-${post.id}-tooltip`}>{post.groupName}</Tooltip>
+              <Tooltip id={`visibility-${id}-tooltip`}>{groupName}</Tooltip>
             )}
           >
             <span data-testid="cohort-icon">
@@ -71,36 +81,43 @@ function PostFooter({
             </span>
           </OverlayTrigger>
         )}
-
+        {closed && (
-        {post.closed
+          <OverlayTrigger
-          && (
+            overlay={(
-            <OverlayTrigger
+              <Tooltip id={`closed-${id}-tooltip`}>
-              overlay={(
+                {intl.formatMessage(messages.postClosed)}
-                <Tooltip id={`closed-${post.id}-tooltip`}>
+              </Tooltip>
-                  {intl.formatMessage(messages.postClosed)}
+            )}
-                </Tooltip>
+          >
-              )}
+            <Icon
-            >
+              src={Locked}
-              <Icon
+              style={{
-                src={Locked}
+                width: '1rem',
-                className="text-primary-500"
+                height: '1rem',
-                style={{
+                marginLeft: '19.5px',
-                  width: '1rem',
+              }}
-                  height: '1rem',
+            />
-                  marginLeft: '19.5px',
+          </OverlayTrigger>
-                }}
+        )}
-              />
-            </OverlayTrigger>
-          )}
       </div>
     </div>
   );
-}
+};
 
 PostFooter.propTypes = {
-  intl: intlShape.isRequired,
+  voteCount: PropTypes.number.isRequired,
-  post: postShape.isRequired,
+  voted: PropTypes.bool.isRequired,
+  following: PropTypes.bool.isRequired,
+  id: PropTypes.string.isRequired,
+  groupId: PropTypes.string,
+  groupName: PropTypes.string,
+  closed: PropTypes.bool.isRequired,
   userHasModerationPrivileges: PropTypes.bool.isRequired,
 };
 
-export default injectIntl(PostFooter);
+PostFooter.defaultProps = {
+  groupId: null,
+  groupName: null,
+};
+
+export default React.memo(PostFooter);

src/discussions/posts/post/PostHeader.jsx

@@ -3,7 +3,7 @@ import PropTypes from 'prop-types';
 
 import classNames from 'classnames';
 
-import { injectIntl, intlShape } from '@edx/frontend-platform/i18n';
+import { useIntl } from '@edx/frontend-platform/i18n';
 import { Avatar, Badge, Icon } from '@edx/paragon';
 
 import { Issue, Question } from '../../../components/icons';
@@ -11,36 +11,35 @@ import { AvatarOutlineAndLabelColors, ThreadType } from '../../../data/constants
 import { AuthorLabel } from '../../common';
 import { useAlertBannerVisible } from '../../data/hooks';
 import messages from './messages';
-import { postShape } from './proptypes';
 
-export function PostAvatar({
+export const PostAvatar = React.memo(({
-  post, authorLabel, fromPostLink, read,
+  author, postType, authorLabel, fromPostLink, read,
-}) {
+}) => {
   const outlineColor = AvatarOutlineAndLabelColors[authorLabel];
 
   const avatarSize = useMemo(() => {
     let size = '2rem';
-    if (post.type === ThreadType.DISCUSSION && !fromPostLink) {
+    if (postType === ThreadType.DISCUSSION && !fromPostLink) {
       size = '2rem';
-    } else if (post.type === ThreadType.QUESTION) {
+    } else if (postType === ThreadType.QUESTION) {
       size = '1.5rem';
     }
     return size;
-  }, [post.type]);
+  }, [postType]);
 
   const avatarSpacing = useMemo(() => {
     let spacing = 'mr-3 ';
-    if (post.type === ThreadType.DISCUSSION && fromPostLink) {
+    if (postType === ThreadType.DISCUSSION && fromPostLink) {
       spacing += 'pt-2 ml-0.5';
-    } else if (post.type === ThreadType.DISCUSSION) {
+    } else if (postType === ThreadType.DISCUSSION) {
       spacing += 'ml-0.5 mt-0.5';
     }
     return spacing;
-  }, [post.type]);
+  }, [postType]);
 
   return (
     <div className={avatarSpacing}>
-      {post.type === ThreadType.QUESTION && (
+      {postType === ThreadType.QUESTION && (
         <Icon
           src={read ? Issue : Question}
           className={classNames('position-absolute bg-white rounded-circle question-icon-size', {
@@ -52,21 +51,22 @@ export function PostAvatar({
         className={classNames('border-0 mt-1', {
           [`outline-${outlineColor}`]: outlineColor,
           'outline-anonymous': !outlineColor,
-          'mt-3 ml-2': post.type === ThreadType.QUESTION && fromPostLink,
+          'mt-3 ml-2': postType === ThreadType.QUESTION && fromPostLink,
-          'avarat-img-position mt-17px': post.type === ThreadType.QUESTION,
+          'avarat-img-position mt-17px': postType === ThreadType.QUESTION,
         })}
         style={{
           height: avatarSize,
           width: avatarSize,
         }}
-        alt={post.author}
+        alt={author}
       />
     </div>
   );
-}
+});
 
 PostAvatar.propTypes = {
-  post: postShape.isRequired,
+  author: PropTypes.string.isRequired,
+  postType: PropTypes.string.isRequired,
   authorLabel: PropTypes.string,
   fromPostLink: PropTypes.bool,
   read: PropTypes.bool,
@@ -78,65 +78,86 @@ PostAvatar.defaultProps = {
   read: false,
 };
 
-function PostHeader({
+const PostHeader = ({
-  intl,
+  abuseFlagged,
-  post,
+  author,
+  authorLabel,
+  closed,
+  createdAt,
+  hasEndorsed,
+  lastEdit,
+  title,
+  postType,
   preview,
-}) {
+}) => {
-  const showAnsweredBadge = preview && post.hasEndorsed && post.type === ThreadType.QUESTION;
+  const intl = useIntl();
-  const authorLabelColor = AvatarOutlineAndLabelColors[post.authorLabel];
+  const showAnsweredBadge = preview && hasEndorsed && postType === ThreadType.QUESTION;
-  const hasAnyAlert = useAlertBannerVisible(post);
+  const authorLabelColor = AvatarOutlineAndLabelColors[authorLabel];
+  const hasAnyAlert = useAlertBannerVisible({
+    author, abuseFlagged, lastEdit, closed,
+  });
 
   return (
     <div className={classNames('d-flex flex-fill mw-100', { 'mt-10px': hasAnyAlert && !preview })}>
       <div className="flex-shrink-0">
-        <PostAvatar post={post} authorLabel={post.authorLabel} />
+        <PostAvatar postType={postType} author={author} authorLabel={authorLabel} />
       </div>
       <div className="align-items-center d-flex flex-row">
         <div className="d-flex flex-column justify-content-start mw-100">
-          {preview
+          {preview ? (
-            ? (
+            <div className="h4 d-flex align-items-center pb-0 mb-0 flex-fill">
-              <div className="h4 d-flex align-items-center pb-0 mb-0 flex-fill">
+              <div className="flex-fill text-truncate" role="heading" aria-level="1">
-                <div className="flex-fill text-truncate" role="heading" aria-level="1">
+                {title}
-                  {post.title}
-                </div>
-                {showAnsweredBadge
-                  && <Badge variant="success">{intl.formatMessage(messages.answered)}</Badge>}
               </div>
-            )
+              {showAnsweredBadge
-            : (
+                  && <Badge variant="success">{intl.formatMessage(messages.answered)}</Badge>}
-              <h5
+            </div>
-                className="mb-0 font-style text-primary-500"
+          ) : (
-                style={{ lineHeight: '21px' }}
+            <h5
-                aria-level="1"
+              className="mb-0 font-style text-primary-500"
-                tabIndex="-1"
+              style={{ lineHeight: '21px' }}
-                accessKey="h"
+              aria-level="1"
-              >
+              tabIndex="-1"
-                {post.title}
+              accessKey="h"
-              </h5>
+            >
-            )}
+              {title}
+            </h5>
+          )}
           <AuthorLabel
-            author={post.author || intl.formatMessage(messages.anonymous)}
+            author={author || intl.formatMessage(messages.anonymous)}
-            authorLabel={post.authorLabel}
+            authorLabel={authorLabel}
             labelColor={authorLabelColor && `text-${authorLabelColor}`}
             linkToProfile
-            postCreatedAt={post.createdAt}
+            postCreatedAt={createdAt}
             postOrComment
           />
         </div>
       </div>
     </div>
   );
-}
+};
 
 PostHeader.propTypes = {
-  intl: intlShape.isRequired,
-  post: postShape.isRequired,
   preview: PropTypes.bool,
+  hasEndorsed: PropTypes.bool.isRequired,
+  postType: PropTypes.string.isRequired,
+  authorLabel: PropTypes.string,
+  author: PropTypes.string.isRequired,
+  title: PropTypes.string.isRequired,
+  createdAt: PropTypes.string.isRequired,
+  abuseFlagged: PropTypes.bool,
+  lastEdit: PropTypes.shape({
+    reason: PropTypes.string,
+  }),
+  closed: PropTypes.bool,
 };
 
 PostHeader.defaultProps = {
+  authorLabel: null,
   preview: false,
+  abuseFlagged: false,
+  lastEdit: {},
+  closed: false,
 };
 
-export default injectIntl(PostHeader);
+export default React.memo(PostHeader);

src/discussions/posts/post/PostLink.jsx

@@ -1,8 +1,9 @@
 /* eslint-disable react/no-unknown-property */
-import React, { useContext } from 'react';
+import React, { useContext, useMemo } from 'react';
 import PropTypes from 'prop-types';
 
 import classNames from 'classnames';
+import { useSelector } from 'react-redux';
 import { Link } from 'react-router-dom';
 
 import { useIntl } from '@edx/frontend-platform/i18n';
@@ -14,37 +15,45 @@ import { AvatarOutlineAndLabelColors, Routes, ThreadType } from '../../../data/c
 import AuthorLabel from '../../common/AuthorLabel';
 import { DiscussionContext } from '../../common/context';
 import { discussionsPath, isPostPreviewAvailable } from '../../utils';
+import { selectThread } from '../data/selectors';
 import messages from './messages';
 import { PostAvatar } from './PostHeader';
 import PostSummaryFooter from './PostSummaryFooter';
-import { postShape } from './proptypes';
 
-function PostLink({
+const PostLink = ({
-  post,
-  isSelected,
-  showDivider,
   idx,
-}) {
+  postId,
+  showDivider,
+}) => {
   const intl = useIntl();
   const {
+    courseId,
+    postId: selectedPostId,
     page,
-    postId,
     enableInContextSidebar,
     category,
     learnerUsername,
   } = useContext(DiscussionContext);
+  const {
+    topicId, hasEndorsed, type, author, authorLabel, abuseFlagged, abuseFlaggedCount, read, commentCount,
+    unreadCommentCount, id, pinned, previewBody, title, voted, voteCount, following, groupId, groupName, createdAt,
+  } = useSelector(selectThread(postId));
   const linkUrl = discussionsPath(Routes.COMMENTS.PAGES[page], {
     0: enableInContextSidebar ? 'in-context' : undefined,
-    courseId: post.courseId,
+    courseId,
-    topicId: post.topicId,
+    topicId,
-    postId: post.id,
+    postId,
     category,
     learnerUsername,
   });
-  const showAnsweredBadge = post.hasEndorsed && post.type === ThreadType.QUESTION;
+  const showAnsweredBadge = hasEndorsed && type === ThreadType.QUESTION;
-  const authorLabelColor = AvatarOutlineAndLabelColors[post.authorLabel];
+  const authorLabelColor = AvatarOutlineAndLabelColors[authorLabel];
-  const canSeeReportedBadge = post.abuseFlagged || post.abuseFlaggedCount;
+  const canSeeReportedBadge = abuseFlagged || abuseFlaggedCount;
-  const read = post.read || (!post.read && post.commentCount !== post.unreadCommentCount);
+  const isPostRead = read || (!read && commentCount !== unreadCommentCount);
+
+  const checkIsSelected = useMemo(() => (
+    window.location.pathname.includes(postId)),
+  [window.location.pathname]);
 
   return (
     <>
@@ -55,19 +64,24 @@ function PostLink({
           })
         }
         to={linkUrl}
-        onClick={() => isSelected(post.id)}
+        aria-current={checkIsSelected ? 'page' : undefined}
-        aria-current={isSelected(post.id) ? 'page' : undefined}
         role="option"
-        tabIndex={(isSelected(post.id) || idx === 0) ? 0 : -1}
+        tabIndex={(checkIsSelected || idx === 0) ? 0 : -1}
       >
         <div
           className={
             classNames('d-flex flex-row pt-2 pb-2 px-4 border-primary-500 position-relative',
-              { 'bg-light-300': read },
+              { 'bg-light-300': isPostRead },
-              { 'post-summary-card-selected': post.id === postId })
+              { 'post-summary-card-selected': id === selectedPostId })
           }
         >
-          <PostAvatar post={post} authorLabel={post.authorLabel} fromPostLink read={read} />
+          <PostAvatar
+            postType={type}
+            author={author}
+            authorLabel={authorLabel}
+            fromPostLink
+            read={isPostRead}
+          />
           <div className="d-flex flex-column flex-fill" style={{ minWidth: 0 }}>
             <div className="d-flex flex-column justify-content-start mw-100 flex-fill" style={{ marginBottom: '-3px' }}>
               <div className="d-flex align-items-center pb-0 mb-0 flex-fill font-weight-500">
@@ -78,14 +92,14 @@ function PostLink({
                         { 'font-weight-bolder': !read })
                     }
                   >
-                    {post.title}
+                    {title}
                   </span>
                   <span class="align-bottom"> </span>
                   <span
                     class="text-gray-700 font-weight-normal font-size-14 font-style align-bottom"
                   >
-                    {isPostPreviewAvailable(post.previewBody)
+                    {isPostPreviewAvailable(previewBody)
-                      ? post.previewBody
+                      ? previewBody
                       : intl.formatMessage(messages.postWithoutPreview)}
                   </span>
                 </Truncate>
@@ -94,7 +108,6 @@ function PostLink({
                     <span className="sr-only">{' '}answered</span>
                   </Icon>
                 )}
-
                 {canSeeReportedBadge && (
                   <Badge
                     variant="danger"
@@ -105,8 +118,7 @@ function PostLink({
                     <span className="sr-only">{' '}reported</span>
                   </Badge>
                 )}
-
+                {pinned && (
-                {post.pinned && (
                   <Icon
                     src={PushPin}
                     className={`post-summary-icons-dimensions text-gray-700
@@ -116,29 +128,40 @@ function PostLink({
               </div>
             </div>
             <AuthorLabel
-              author={post.author || intl.formatMessage(messages.anonymous)}
+              author={author || intl.formatMessage(messages.anonymous)}
-              authorLabel={post.authorLabel}
+              authorLabel={authorLabel}
               labelColor={authorLabelColor && `text-${authorLabelColor}`}
             />
-            <PostSummaryFooter post={post} preview showNewCountLabel={read} />
+            <PostSummaryFooter
+              postId={id}
+              voted={voted}
+              voteCount={voteCount}
+              following={following}
+              commentCount={commentCount}
+              unreadCommentCount={unreadCommentCount}
+              groupId={groupId}
+              groupName={groupName}
+              createdAt={createdAt}
+              preview
+              showNewCountLabel={isPostRead}
+            />
           </div>
         </div>
-        {!showDivider && post.pinned && <div className="pt-1 bg-light-500 border-top border-light-700" />}
+        {!showDivider && pinned && <div className="pt-1 bg-light-500 border-top border-light-700" />}
       </Link>
     </>
   );
-}
+};
 
 PostLink.propTypes = {
-  post: postShape.isRequired,
-  isSelected: PropTypes.func.isRequired,
-  showDivider: PropTypes.bool,
   idx: PropTypes.number,
+  postId: PropTypes.string.isRequired,
+  showDivider: PropTypes.bool,
 };
 
 PostLink.defaultProps = {
-  showDivider: true,
   idx: -1,
+  showDivider: true,
 };
 
-export default PostLink;
+export default React.memo(PostLink);

src/discussions/posts/post/PostSummaryFooter.jsx

@@ -4,7 +4,7 @@ import PropTypes from 'prop-types';
 import { useSelector } from 'react-redux';
 import * as timeago from 'timeago.js';
 
-import { injectIntl, intlShape } from '@edx/frontend-platform/i18n';
+import { useIntl } from '@edx/frontend-platform/i18n';
 import {
   Badge, Icon, OverlayTrigger, Tooltip,
 } from '@edx/paragon';
@@ -16,78 +16,86 @@ import { People, QuestionAnswer, QuestionAnswerOutline } from '../../../componen
 import timeLocale from '../../common/time-locale';
 import { selectUserHasModerationPrivileges } from '../../data/selectors';
 import messages from './messages';
-import { postShape } from './proptypes';
 
-function PostSummaryFooter({
+const PostSummaryFooter = ({
-  post,
+  postId,
-  intl,
+  voted,
+  voteCount,
+  following,
+  commentCount,
+  unreadCommentCount,
+  groupId,
+  groupName,
+  createdAt,
   preview,
   showNewCountLabel,
-}) {
+}) => {
-  const userHasModerationPrivileges = useSelector(selectUserHasModerationPrivileges);
   timeago.register('time-locale', timeLocale);
+  const intl = useIntl();
+  const userHasModerationPrivileges = useSelector(selectUserHasModerationPrivileges);
+
   return (
     <div className="d-flex align-items-center text-gray-700" style={{ height: '24px' }}>
       <div className="d-flex align-items-center mr-4.5">
         <OverlayTrigger
           overlay={(
-            <Tooltip id={`liked-${post.id}-tooltip`}>
+            <Tooltip id={`liked-${postId}-tooltip`}>
-              {intl.formatMessage(post.voted ? messages.likedPost : messages.postLikes)}
+              {intl.formatMessage(voted ? messages.likedPost : messages.postLikes)}
             </Tooltip>
           )}
         >
-          <Icon src={post.voted ? ThumbUpFilled : ThumbUpOutline} className="post-summary-like-dimensions mr-0.5">
+          <Icon src={voted ? ThumbUpFilled : ThumbUpOutline} className="post-summary-like-dimensions mr-0.5">
-            <span className="sr-only">{' '}{intl.formatMessage(post.voted ? messages.likedPost : messages.postLikes)}</span>
+            <span className="sr-only">{' '}{intl.formatMessage(voted ? messages.likedPost : messages.postLikes)}</span>
           </Icon>
         </OverlayTrigger>
         <div className="font-style">
-          {(post.voteCount && post.voteCount > 0) ? post.voteCount : null}
+          {(voteCount && voteCount > 0) ? voteCount : null}
         </div>
       </div>
 
       <OverlayTrigger
         overlay={(
-          <Tooltip id={`follow-${post.id}-tooltip`}>
+          <Tooltip id={`follow-${postId}-tooltip`}>
-            {intl.formatMessage(post.following ? messages.followed : messages.notFollowed)}
+            {intl.formatMessage(following ? messages.followed : messages.notFollowed)}
           </Tooltip>
         )}
       >
-        <Icon src={post.following ? StarFilled : StarOutline} className="post-summary-icons-dimensions mr-0.5">
+        <Icon src={following ? StarFilled : StarOutline} className="post-summary-icons-dimensions mr-0.5">
           <span className="sr-only">
-            {' '}{intl.formatMessage(post.following ? messages.srOnlyFollowDescription : messages.srOnlyUnFollowDescription)}
+            {' '}{intl.formatMessage(following ? messages.srOnlyFollowDescription : messages.srOnlyUnFollowDescription)}
           </span>
         </Icon>
       </OverlayTrigger>
 
-      {preview && post.commentCount > 1 && (
+      {preview && commentCount > 1 && (
         <div className="d-flex align-items-center ml-4.5 text-gray-700 font-style font-size-12">
           <OverlayTrigger
             overlay={(
-              <Tooltip id={`follow-${post.id}-tooltip`}>
+              <Tooltip id={`follow-${postId}-tooltip`}>
                 {intl.formatMessage(messages.activity)}
               </Tooltip>
             )}
           >
             <Icon
-              src={post.unreadCommentCount ? QuestionAnswer : QuestionAnswerOutline}
+              src={unreadCommentCount ? QuestionAnswer : QuestionAnswerOutline}
               className="post-summary-comment-count-dimensions mr-0.5"
             >
               <span className="sr-only">{' '} {intl.formatMessage(messages.activity)}</span>
             </Icon>
           </OverlayTrigger>
-          {post.commentCount}
+          {commentCount}
         </div>
       )}
-      {showNewCountLabel && preview && post?.unreadCommentCount > 0 && post.commentCount > 1 && (
+      {showNewCountLabel && preview && unreadCommentCount > 0 && commentCount > 1 && (
         <Badge variant="light" className="ml-2">
-          {intl.formatMessage(messages.newLabel, { count: post.unreadCommentCount })}
+          {intl.formatMessage(messages.newLabel, { count: unreadCommentCount })}
         </Badge>
       )}
       <div className="d-flex flex-fill justify-content-end align-items-center">
-        {post.groupId && userHasModerationPrivileges && (
+        {groupId && userHasModerationPrivileges && (
           <OverlayTrigger
             overlay={(
-              <Tooltip id={`visibility-${post.id}-tooltip`}>{post.groupName}</Tooltip>
+              <Tooltip id={`visibility-${postId}-tooltip`}>{groupName}</Tooltip>
             )}
           >
             <span data-testid="cohort-icon" className="mr-2">
@@ -98,17 +106,24 @@ function PostSummaryFooter({
             </span>
           </OverlayTrigger>
         )}
-        <span title={post.createdAt} className="text-gray-700 post-summary-timestamp ml-0.5">
+        <span title={createdAt} className="text-gray-700 post-summary-timestamp ml-0.5">
-          {timeago.format(post.createdAt, 'time-locale')}
+          {timeago.format(createdAt, 'time-locale')}
         </span>
       </div>
     </div>
   );
-}
+};
 
 PostSummaryFooter.propTypes = {
-  intl: intlShape.isRequired,
+  postId: PropTypes.string.isRequired,
-  post: postShape.isRequired,
+  voted: PropTypes.bool.isRequired,
+  voteCount: PropTypes.number.isRequired,
+  following: PropTypes.bool.isRequired,
+  commentCount: PropTypes.number.isRequired,
+  unreadCommentCount: PropTypes.number.isRequired,
+  groupId: PropTypes.number,
+  groupName: PropTypes.string,
+  createdAt: PropTypes.string.isRequired,
   preview: PropTypes.bool,
   showNewCountLabel: PropTypes.bool,
 };
@@ -116,6 +131,8 @@ PostSummaryFooter.propTypes = {
 PostSummaryFooter.defaultProps = {
   preview: false,
   showNewCountLabel: false,
+  groupId: null,
+  groupName: null,
 };
 
-export default injectIntl(PostSummaryFooter);
+export default React.memo(PostSummaryFooter);

src/discussions/topics/TopicsView.jsx

@@ -1,4 +1,6 @@
-import React, { useContext, useEffect } from 'react';
+import React, {
+  useCallback, useContext, useEffect, useMemo,
+} from 'react';
 
 import { useDispatch, useSelector } from 'react-redux';
 import { useParams } from 'react-router';
@@ -16,49 +18,57 @@ import LegacyTopicGroup from './topic-group/LegacyTopicGroup';
 import Topic from './topic-group/topic/Topic';
 import countFilteredTopics from './utils';
 
-function CourseWideTopics() {
+const CourseWideTopics = () => {
   const { category } = useParams();
   const filter = useSelector(selectTopicFilter);
   const nonCoursewareTopics = useSelector(selectNonCoursewareTopics);
-  const filteredNonCoursewareTopics = nonCoursewareTopics.filter(item => (filter
+
-    ? item.name.toLowerCase().includes(filter)
+  const filteredNonCoursewareTopics = useMemo(() => (
-    : true
+    nonCoursewareTopics.filter(item => (
-  ));
+      filter ? item.name.toLowerCase().includes(filter) : true
+    ))), [nonCoursewareTopics, filter]);
 
   return (nonCoursewareTopics && category === undefined)
     && filteredNonCoursewareTopics.map((topic, index) => (
       <Topic
-        topic={topic}
+        topicId={topic.id}
         key={topic.id}
         index={index}
         showDivider={(filteredNonCoursewareTopics.length - 1) !== index}
       />
     ));
-}
+};
 
-function LegacyCoursewareTopics() {
+const LegacyCoursewareTopics = () => {
   const { category } = useParams();
-  const categories = useSelector(selectCategories)
+  const categories = useSelector(selectCategories);
-    .filter(cat => (category ? cat === category : true));
+
-  return categories?.map(
+  const filteredCategories = useMemo(() => (
-    topicGroup => (
+    categories.filter(cat => (category ? cat === category : true))
+  ), [categories, category]);
+
+  return filteredCategories?.map(
+    categoryId => (
       <LegacyTopicGroup
-        id={topicGroup}
+        categoryId={categoryId}
-        category={topicGroup}
+        key={categoryId}
-        key={topicGroup}
       />
     ),
   );
-}
+};
 
-function TopicsView() {
+const TopicsView = () => {
+  const dispatch = useDispatch();
   const provider = useSelector(selectDiscussionProvider);
   const topicFilter = useSelector(selectTopicFilter);
   const topicsSelector = useSelector(({ topics }) => topics);
   const filteredTopicsCount = useSelector(({ topics }) => topics.results.count);
   const loadingStatus = useSelector(({ topics }) => topics.status);
   const { courseId } = useContext(DiscussionContext);
-  const dispatch = useDispatch();
+
+  const handleOnClear = useCallback(() => {
+    dispatch(setFilter(''));
+  }, []);
 
   useEffect(() => {
     // Don't load till the provider information is available
@@ -79,7 +89,7 @@ function TopicsView() {
           text={topicFilter}
           count={filteredTopicsCount}
           loadingStatus={loadingStatus}
-          onClear={() => dispatch(setFilter(''))}
+          onClear={handleOnClear}
         />
       )}
       <div className="list-group list-group-flush flex-fill" role="list" onKeyDown={e => handleKeyDown(e)}>
@@ -94,8 +104,6 @@ function TopicsView() {
       }
     </div>
   );
-}
+};
-
-TopicsView.propTypes = {};
 
 export default TopicsView;

src/discussions/topics/data/selectors.js

@@ -13,6 +13,10 @@ export const selectTopicsInCategory = (categoryId) => state => (
   state.topics.topicsInCategory[categoryId]?.map(id => state.topics.topics[id]) || []
 );
 
+export const selectTopicsInCategoryIds = (categoryId) => state => (
+  state.topics.topicsInCategory[categoryId] || []
+);
+
 export const selectTopics = state => state.topics.topics;
 export const selectCoursewareTopics = createSelector(
   selectCategories,

src/discussions/topics/topic-group/LegacyTopicGroup.jsx

@@ -3,27 +3,23 @@ import PropTypes from 'prop-types';
 
 import { useSelector } from 'react-redux';
 
-import { selectTopicsInCategory } from '../data/selectors';
+import { selectTopicsInCategoryIds } from '../data/selectors';
 import TopicGroupBase from './TopicGroupBase';
 
-function LegacyTopicGroup({
+const LegacyTopicGroup = ({ categoryId }) => {
-  id,
+  const topicsIds = useSelector(selectTopicsInCategoryIds(categoryId));
-  category,
+
-}) {
-  const topics = useSelector(selectTopicsInCategory(category));
   return (
-    <TopicGroupBase groupId={id} groupTitle={category} topics={topics} />
+    <TopicGroupBase groupId={categoryId} groupTitle={categoryId} topicsIds={topicsIds} />
   );
-}
+};
 
 LegacyTopicGroup.propTypes = {
-  id: PropTypes.string,
+  categoryId: PropTypes.string,
-  category: PropTypes.string,
 };
 
 LegacyTopicGroup.defaultProps = {
-  id: null,
+  categoryId: null,
-  category: null,
 };
 
-export default LegacyTopicGroup;
+export default React.memo(LegacyTopicGroup);

src/discussions/topics/topic-group/TopicGroupBase.jsx

@@ -1,43 +1,63 @@
-import React, { useContext } from 'react';
+import React, { useContext, useMemo } from 'react';
 import PropTypes from 'prop-types';
 
 import { useSelector } from 'react-redux';
 import { Link } from 'react-router-dom';
 
-import { injectIntl, intlShape } from '@edx/frontend-platform/i18n';
+import { useIntl } from '@edx/frontend-platform/i18n';
 
 import { Routes } from '../../../data/constants';
 import { DiscussionContext } from '../../common/context';
 import { discussionsPath } from '../../utils';
-import { selectTopicFilter } from '../data/selectors';
+import { selectTopicFilter, selectTopicsById } from '../data/selectors';
 import messages from '../messages';
-import Topic, { topicShape } from './topic/Topic';
+import Topic from './topic/Topic';
 
-function TopicGroupBase({
+const TopicGroupBase = ({
   groupId,
   groupTitle,
   linkToGroup,
-  topics,
+  topicsIds,
-  intl,
+}) => {
-}) {
+  const intl = useIntl();
   const { courseId } = useContext(DiscussionContext);
   const filter = useSelector(selectTopicFilter);
+  const topics = useSelector(selectTopicsById(topicsIds));
   const hasTopics = topics.length > 0;
-  const matchesFilter = filter
-    ? groupTitle?.toLowerCase().includes(filter)
-    : true;
 
-  const filteredTopicElements = topics.filter(
+  const matchesFilter = useMemo(() => (
-    topic => (filter
+    filter ? groupTitle?.toLowerCase().includes(filter) : true
-      ? (topic.name.toLowerCase().includes(filter) || matchesFilter)
+  ), [filter, groupTitle]);
-      : true
+
-    ),
+  const filteredTopicElements = useMemo(() => (
-  );
+    topics.filter(topic => (
+      filter ? (topic.name.toLowerCase().includes(filter) || matchesFilter) : true
+    ))
+  ), [topics, filter, matchesFilter]);
 
   const hasFilteredSubtopics = (filteredTopicElements.length > 0);
+
+  const renderFilteredTopics = useMemo(() => {
+    if (!hasFilteredSubtopics) {
+      return <></>;
+    }
+
+    return (
+      filteredTopicElements.map((topic, index) => (
+        <Topic
+          topicId={topic.id}
+          key={topic.id}
+          index={index}
+          showDivider={(filteredTopicElements.length - 1) !== index}
+        />
+      ))
+    );
+  }, [filteredTopicElements]);
+
   if (!hasTopics || (!matchesFilter && !hasFilteredSubtopics)) {
     return null;
   }
+
   return (
     <div
       className="discussion-topic-group d-flex flex-column text-primary-500"
@@ -45,43 +65,34 @@ function TopicGroupBase({
       data-testid="topic-group"
     >
       <div className="pt-2.5 px-4 font-weight-bold">
-        {linkToGroup && groupId
+        {linkToGroup && groupId ? (
-          ? (
+          <Link
-            <Link
+            className="text-decoration-none text-primary-500"
-              className="text-decoration-none text-primary-500"
+            to={discussionsPath(Routes.TOPICS.CATEGORY, {
-              to={discussionsPath(Routes.TOPICS.CATEGORY, {
+              courseId,
-                courseId,
+              category: groupId,
-                category: groupId,
+            })}
-              })}
+          >
-            >
+            {groupTitle}
-              {groupTitle}
+          </Link>
-            </Link>
+        ) : (
-          ) : (
+          groupTitle || intl.formatMessage(messages.unnamedTopicCategories)
-            groupTitle || intl.formatMessage(messages.unnamedTopicCategories)
+        )}
-          )}
       </div>
-      {filteredTopicElements.map((topic, index) => (
+      {renderFilteredTopics}
-        <Topic
-          topic={topic}
-          key={topic.id}
-          index={index}
-          showDivider={(filteredTopicElements.length - 1) !== index}
-        />
-      ))}
     </div>
   );
-}
+};
 
 TopicGroupBase.propTypes = {
   groupId: PropTypes.string.isRequired,
   groupTitle: PropTypes.string.isRequired,
-  topics: PropTypes.arrayOf(topicShape).isRequired,
+  topicsIds: PropTypes.arrayOf(PropTypes.string).isRequired,
   linkToGroup: PropTypes.bool,
-  intl: intlShape.isRequired,
 };
 
 TopicGroupBase.defaultProps = {
   linkToGroup: true,
 };
 
-export default injectIntl(TopicGroupBase);
+export default React.memo(TopicGroupBase);

src/discussions/topics/topic-group/topic/Topic.jsx

@@ -1,5 +1,5 @@
 /* eslint-disable no-unused-vars, react/forbid-prop-types */
-import React from 'react';
+import React, { useCallback } from 'react';
 import PropTypes from 'prop-types';
 
 import classNames from 'classnames';
@@ -7,31 +7,31 @@ import { useSelector } from 'react-redux';
 import { useParams } from 'react-router';
 import { Link } from 'react-router-dom';
 
-import { injectIntl, intlShape } from '@edx/frontend-platform/i18n';
+import { useIntl } from '@edx/frontend-platform/i18n';
 import { Icon, OverlayTrigger, Tooltip } from '@edx/paragon';
 import { HelpOutline, PostOutline, Report } from '@edx/paragon/icons';
 
 import { Routes } from '../../../../data/constants';
 import { selectUserHasModerationPrivileges, selectUserIsGroupTa } from '../../../data/selectors';
 import { discussionsPath } from '../../../utils';
+import { selectTopic } from '../../data/selectors';
 import messages from '../../messages';
 
-function Topic({
+const Topic = ({ topicId, showDivider, index }) => {
-  topic,
+  const intl = useIntl();
-  showDivider,
-  index,
-  intl,
-}) {
   const { courseId } = useParams();
-  const topicUrl = discussionsPath(Routes.TOPICS.TOPIC, {
+  const topic = useSelector(selectTopic(topicId));
-    courseId,
+  const {
-    topicId: topic.id,
+    id, inactiveFlags, activeFlags, name, threadCounts,
-  });
+  } = topic;
   const userHasModerationPrivileges = useSelector(selectUserHasModerationPrivileges);
   const userIsGroupTa = useSelector(selectUserIsGroupTa);
-  const { inactiveFlags, activeFlags } = topic;
   const canSeeReportedStats = (activeFlags || inactiveFlags) && (userHasModerationPrivileges || userIsGroupTa);
-  const isSelected = (id) => window.location.pathname.includes(id);
+  const topicUrl = discussionsPath(Routes.TOPICS.TOPIC, { courseId, topicId });
+
+  const isSelected = useCallback((selectedId) => (
+    window.location.pathname.includes(selectedId)
+  ), []);
 
   return (
     <Link
@@ -40,18 +40,18 @@ function Topic({
           'border-bottom border-light-400': showDivider,
         })
       }
-      data-topic-id={topic.id}
+      data-topic-id={id}
       to={topicUrl}
-      onClick={() => isSelected(topic.id)}
+      onClick={() => isSelected(id)}
-      aria-current={isSelected(topic.id) ? 'page' : undefined}
+      aria-current={isSelected(id) ? 'page' : undefined}
       role="option"
-      tabIndex={(isSelected(topic.id) || index === 0) ? 0 : -1}
+      tabIndex={(isSelected(id) || index === 0) ? 0 : -1}
     >
       <div className="d-flex flex-row pt-2.5 pb-2 px-4">
         <div className="d-flex flex-column flex-fill" style={{ minWidth: 0 }}>
           <div className="d-flex flex-column justify-content-start mw-100 flex-fill">
             <div className="topic-name text-truncate">
-              {topic.name || intl.formatMessage(messages.unnamedTopicSubCategories)}
+              {name || intl.formatMessage(messages.unnamedTopicSubCategories)}
             </div>
           </div>
           <div className="d-flex align-items-center mt-2.5" style={{ marginBottom: '2px' }}>
@@ -61,7 +61,7 @@ function Topic({
                 <Tooltip>
                   <div className="d-flex flex-column align-items-start">
                     {intl.formatMessage(messages.discussions, {
-                      count: topic.threadCounts?.discussion || 0,
+                      count: threadCounts?.discussion || 0,
                     })}
                   </div>
                 </Tooltip>
@@ -69,7 +69,7 @@ function Topic({
             >
               <div className="d-flex align-items-center mr-3.5">
                 <Icon src={PostOutline} className="icon-size mr-2" />
-                {topic.threadCounts?.discussion || 0}
+                {threadCounts?.discussion || 0}
               </div>
             </OverlayTrigger>
             <OverlayTrigger
@@ -78,7 +78,7 @@ function Topic({
                 <Tooltip>
                   <div className="d-flex flex-column align-items-start">
                     {intl.formatMessage(messages.questions, {
-                      count: topic.threadCounts?.question || 0,
+                      count: threadCounts?.question || 0,
                     })}
                   </div>
                 </Tooltip>
@@ -86,7 +86,7 @@ function Topic({
             >
               <div className="d-flex align-items-center mr-3.5">
                 <Icon src={HelpOutline} className="icon-size mr-2" />
-                {topic.threadCounts?.question || 0}
+                {threadCounts?.question || 0}
               </div>
             </OverlayTrigger>
             {Boolean(canSeeReportedStats) && (
@@ -121,7 +121,7 @@ function Topic({
       {!showDivider && <div className="divider pt-1 bg-light-500 border-top border-light-700" />}
     </Link>
   );
-}
+};
 
 export const topicShape = PropTypes.shape({
   name: PropTypes.string,
@@ -130,9 +130,9 @@ export const topicShape = PropTypes.shape({
   discussions: PropTypes.number,
   flags: PropTypes.number,
 });
+
 Topic.propTypes = {
-  intl: intlShape.isRequired,
+  topicId: PropTypes.string.isRequired,
-  topic: topicShape.isRequired,
   showDivider: PropTypes.bool,
   index: PropTypes.number,
 };
@@ -142,4 +142,4 @@ Topic.defaultProps = {
   index: -1,
 };
 
-export default injectIntl(Topic);
+export default React.memo(Topic);

src/discussions/tours/DiscussionsProductTour.jsx

@@ -1,17 +1,17 @@
-import { useEffect } from 'react';
+import React, { useEffect } from 'react';
 
 import isEmpty from 'lodash/isEmpty';
 import { useDispatch } from 'react-redux';
 
-import { injectIntl, intlShape } from '@edx/frontend-platform/i18n';
 import { ProductTour } from '@edx/paragon';
 
 import { useTourConfiguration } from '../data/hooks';
 import { fetchDiscussionTours } from './data/thunks';
 
-function DiscussionsProductTour({ intl }) {
+const DiscussionsProductTour = () => {
   const dispatch = useDispatch();
-  const config = useTourConfiguration(intl);
+  const config = useTourConfiguration();
+
   useEffect(() => {
     dispatch(fetchDiscussionTours());
   }, []);
@@ -25,10 +25,6 @@ function DiscussionsProductTour({ intl }) {
       )}
     </>
   );
-}
-
-DiscussionsProductTour.propTypes = {
-  intl: intlShape.isRequired,
 };
 
-export default injectIntl(DiscussionsProductTour);
+export default DiscussionsProductTour;

src/discussions/utils.js

@@ -1,6 +1,8 @@
-/* eslint-disable import/prefer-default-export */
+import { useCallback, useContext, useMemo } from 'react';
+
 import { getIn } from 'formik';
 import { uniqBy } from 'lodash';
+import { useSelector } from 'react-redux';
 import { generatePath, useRouteMatch } from 'react-router';
 
 import { getConfig } from '@edx/frontend-platform';
@@ -10,6 +12,8 @@ import {
 
 import { InsertLink } from '../components/icons';
 import { ContentActions, Routes, ThreadType } from '../data/constants';
+import { ContentSelectors } from './data/constants';
+import { PostCommentsContext } from './post-comments/postCommentsContext';
 import messages from './messages';
 
 /**
@@ -175,20 +179,26 @@ export const ACTIONS_LIST = [
   },
 ];
 
-export function useActions(content) {
+export function useActions(contentType, id) {
-  const checkConditions = (item, conditions) => (
+  const postType = useContext(PostCommentsContext);
+  const content = { ...useSelector(ContentSelectors[contentType](id)), postType };
+
+  const checkConditions = useCallback((item, conditions) => (
     conditions
       ? Object.keys(conditions)
         .map(key => item[key] === conditions[key])
         .every(condition => condition === true)
       : true
-  );
+  ), []);
-  return ACTIONS_LIST.filter(
+
+  const actions = useMemo(() => ACTIONS_LIST.filter(
     ({
       action,
       conditions = null,
     }) => checkPermissions(content, action) && checkConditions(content, conditions),
-  );
+  ), [content]);
+
+  return actions;
 }
 
 export const formikCompatibleHandler = (formikHandler, name) => (value) => formikHandler({

src/index.scss

@@ -178,18 +178,18 @@ $fa-font-path: "~font-awesome/fonts";
   background-color: unset !important;
 }
 
-.learner>a:hover {
+.learner > a:hover {
   background-color: #F2F0EF;
 }
 
 .py-10px {
-  padding-top: 10px;
+  padding-top: 10px !important;
-  padding-bottom: 10px;
+  padding-bottom: 10px !important;
 }
 
 .py-8px {
-  padding-top: 8px;
+  padding-top: 8px !important;
-  padding-bottom: 8px;
+  padding-bottom: 8px !important;
 }
 
 .pb-10px {
@@ -530,3 +530,10 @@ header {
   position: relative;
   background-color: #fff;
 }
+
+.spinner-container {
+  position: absolute;
+  top: 50%;
+  left: 50%;
+  transform: translate(-50%, -50%);
+}