fix: hide new post indicator on thread open

This fixes the removal of the new post indicator in the Discussion XBlock once a thread has been opened.

common/static/common/js/discussion/views/discussion_inline_view.js

@@ -154,6 +154,7 @@
             });
             this.threadView.render();
             this.listenTo(this.threadView.showView, 'thread:_delete', this.navigateToAllPosts);
+            this.$(".forum-nav-thread[data-id='" + threadId + "']").removeClass('never-read');
             this.threadListView.$el.addClass('is-hidden');
             this.$('.inline-thread').removeClass('is-hidden');
         },

common/static/common/js/spec/discussion/view/discussion_inline_view_spec.js

@@ -35,6 +35,7 @@
         });
 
         createTestView = function(test) {
+            var testView;
             var courseSettings = DiscussionSpecHelper.createTestCourseSettings({
                 groups: [
                     {
@@ -62,7 +63,7 @@
                     children: []
                 }
             });
-            var testView = new DiscussionInlineView({
+            testView = new DiscussionInlineView({
                 el: $('.discussion-module')
             });
             testView.render();
@@ -234,6 +235,22 @@
                 // Verify that the individual thread is no longer shown
                 expect(testView.$('.group-visibility-label').length).toBe(0);
             });
+
+            it('marks a thread as read once it is opened', function() {
+                var testView = createTestView(this);
+                var thread;
+                showDiscussion(this, testView);
+                thread = testView.$('.forum-nav-thread');
+
+                // The thread is marked as unread.
+                expect(thread).toHaveClass('never-read');
+
+                // Navigate to the thread.
+                thread.find('.forum-nav-thread-link').click();
+
+                // The thread is no longer marked as unread.
+                expect(thread).not.toHaveClass('never-read');
+            });
         });
     });
 }());