Fix bug in inline discussion post creation

Commit 994ccd1 contained a bug that caused new posts created via the
courseware interface to not get posted to the correct topic. They would
appear to work but would actually be posted to the "undefined" topic.
This has now been fixed.

JIRA: FOR-154

common/static/coffee/spec/discussion/view/new_post_view_spec.coffee

@@ -23,6 +23,17 @@ describe "NewPostView", ->
                 </div>
             </script>
 
+            <script aria-hidden="true" type="text/template" id="new-post-inline-template">
+                <div class="inner-wrapper">
+                    <div class="new-post-form-errors">
+                    </div>
+                    <form class="new-post-form">
+                        <%= editor_html %>
+                        <%= options_html %>
+                    </form>
+                </div>
+            </script>
+
             <script aria-hidden="true" type="text/template" id="new-post-menu-entry-template">
                 <li role="menuitem"><a href="#" class="topic" data-discussion_id="<%- id %>" aria-describedby="topic-name-span-<%- id %>" cohorted="<%- is_cohorted %>"><%- text %></a></li>
             </script>
@@ -92,6 +103,9 @@ describe "NewPostView", ->
         window.$$course_id = "edX/999/test"
         spyOn(DiscussionUtil, "makeWmdEditor")
         @discussion = new Discussion([], {pages: 1})
+
+    describe "Drop down works correct", ->
+      beforeEach ->
         @view = new NewPostView(
           el: $(".new-post-article"),
           collection: @discussion,
@@ -122,8 +136,6 @@ describe "NewPostView", ->
         @parent_category_text = "Basic Question Types"
         @selected_option_text = "Selection From Options"
 
-    describe "Drop down works correct", ->
-
       it "completely show parent category and sub-category", ->
         complete_text = @parent_category_text + " / " + @selected_option_text
         selected_text_width = @view.getNameWidth(complete_text)
@@ -158,3 +170,24 @@ describe "NewPostView", ->
         @view.$el.find( "ul.topic_menu li[role='menuitem'] > a" )[1].click()
         dropdown_text = @view.$el.find(".form-topic-drop > a").text()
         expect(dropdown_text.indexOf("/ span>")).toEqual(-1)
+
+    it "posts to the correct URL", ->
+      topicId = "test_topic"
+      spyOn($, "ajax").andCallFake(
+        (params) ->
+          expect(params.url.path()).toEqual(DiscussionUtil.urlFor("create_thread", topicId))
+          {always: ->}
+      )
+      view = new NewPostView(
+        el: $(".new-post-article"),
+        collection: @discussion,
+        course_settings: new DiscussionCourseSettings({
+          allow_anonymous: false,
+          allow_anonymous_to_peers: false
+        }),
+        mode: "inline",
+        topicId: topicId
+      )
+      view.render()
+      view.$(".new-post-form").submit()
+      expect($.ajax).toHaveBeenCalled()

common/static/coffee/src/discussion/discussion_module_view.coffee

@@ -107,7 +107,8 @@ if Backbone?
       @newPostView = new NewPostView(
         el: @newPostForm,
         collection: @discussion,
-        course_settings: @course_settings
+        course_settings: @course_settings,
+        topicId: discussionId
       )
       @newPostView.render()
       @discussion.on "add", @addThread

common/static/coffee/src/discussion/views/new_post_view.coffee

@@ -7,6 +7,7 @@ if Backbone?
               throw new Error("invalid mode: " + @mode)
           @course_settings = options.course_settings
           @maxNameWidth = 100
+          @topicId = options.topicId
 
       render: () ->
           if @mode is "tab"