slight behavior change

lms/static/coffee/src/discussion/content.coffee

@@ -76,6 +76,7 @@ initializeFollowThread = (thread) ->
           autowatch: autowatch
         error: Discussion.formErrorHandler($local(".discussion-errors"))
         success: (response, textStatus) ->
+          Discussion.clearFormErrors($local(".discussion-errors"))
           $comment = $(response.html)
           $content.children(".comments").prepend($comment)
           Discussion.setWmdContent $content, $local, "reply-body", ""
@@ -151,6 +152,7 @@ initializeFollowThread = (thread) ->
         data: {title: title, body: body, tags: tags},
         error: Discussion.formErrorHandler($local(".discussion-update-errors"))
         success: (response, textStatus) ->
+          Discussion.clearFormErrors($local(".discussion-update-errors"))
           $discussionContent.replaceWith(response.html)
           Discussion.extendContentInfo response.content['id'], response['annotated_content_info']
           Discussion.initializeContent($content)
@@ -179,6 +181,7 @@ initializeFollowThread = (thread) ->
         data: {body: body}
         error: Discussion.formErrorHandler($local(".discussion-update-errors"))
         success: (response, textStatus) ->
+          Discussion.clearFormErrors($local(".discussion-update-errors"))
           $discussionContent.replaceWith(response.html)
           Discussion.extendContentInfo response.content['id'], response['annotated_content_info']
           Discussion.initializeContent($content)

lms/static/coffee/src/discussion/discussion.coffee

@@ -48,8 +48,12 @@ initializeFollowDiscussion = (discussion) ->
           tags: tags
         error: Discussion.formErrorHandler($local(".new-post-form-errors"))
         success: (response, textStatus) ->
+          Discussion.clearFormErrors($local(".new-post-form-errors"))
           $thread = $(response.html)
           $discussion.children(".threads").prepend($thread)
+          $local(".new-post-title").val("")
+          Discussion.setWmdContent $discussion, $local, "new-post-body", ""
+          $local(".new-post-tags").val("")
           if $discussion.hasClass("inline-discussion")
             $local(".new-post-form").addClass("collapsed")
           else if $discussion.hasClass("forum-discussion")

lms/static/coffee/src/discussion/utils.coffee

@@ -99,6 +99,9 @@ wmdEditors = {}
         for error in response.errors
           errorsField.append($("<li>").addClass("new-post-form-error").html(error))
 
+  clearFormErrors: (errorsField) ->
+    errorsField.empty()
+    
   postMathJaxProcessor: (text) ->
     RE_INLINEMATH = /^\$([^\$]*)\$/g
     RE_DISPLAYMATH = /^\$\$([^\$]*)\$\$/g

lms/static/sass/_discussion.scss

@@ -700,6 +700,7 @@ $tag-text-color: #5b614f;
     &.collapsed {
       .new-post-title {
         display: none;
+        visibility: hidden;
       }
 
       .wmd-button-row {