need to make path_to_location a dictionary since it needs to be keyed by the location

lms/djangoapps/django_comment_client/utils.py

@@ -166,6 +166,7 @@ def initialize_discussion_info(course):
     # get all discussion models within this course_id
     all_modules = modulestore().get_items(['i4x', course.location.org, course.location.course, 'discussion', None], course_id=course_id)
 
+    path_to_locations = {}
     for module in all_modules:
         skip_module = False
         for key in ('id', 'discussion_category', 'for'):
@@ -176,7 +177,7 @@ def initialize_discussion_info(course):
         # cdodge: pre-compute the path_to_location. Note this can throw an exception for any
         # dangling discussion modules
         try:
-            _DISCUSSIONINFO[course.id]['path_to_location'] = path_to_location(modulestore(), course.id, module.location)
+            path_to_locations[module.location] = path_to_location(modulestore(), course.id, module.location)
         except NoPathToItem:
             log.warning("Could not compute path_to_location for {0}. Perhaps this is an orphaned discussion module?!? Skipping...".format(module.location))
             skip_module = True
@@ -245,6 +246,7 @@ def initialize_discussion_info(course):
     _DISCUSSIONINFO[course.id]['id_map'] = discussion_id_map
     _DISCUSSIONINFO[course.id]['category_map'] = category_map
     _DISCUSSIONINFO[course.id]['timestamp'] = datetime.now()
+    _DISCUSSIONINFO[course.id]['path_to_location'] = path_to_locations
 
 
 class JsonResponse(HttpResponse):
@@ -402,8 +404,8 @@ def get_courseware_context(content, course):
         title = id_map[id]["title"]
 
         # cdodge: did we pre-compute, if so, then let's use that rather than recomputing
-        if 'path_to_location' in _DISCUSSIONINFO[course.id]:
-            (course_id, chapter, section, position) = _DISCUSSIONINFO[course.id]['path_to_location']
+        if 'path_to_location' in _DISCUSSIONINFO[course.id] and location in _DISCUSSIONINFO[course.id]['path_to_location']:
+            (course_id, chapter, section, position) = _DISCUSSIONINFO[course.id]['path_to_location'][location]
         else:
             (course_id, chapter, section, position) = path_to_location(modulestore(), course.id, location)