Fix issues with duplicate discussion targets.

When two or more instances of Discussion XBlock were configured
with the same discussion target (Category/Subcategory),
only one of the blocks would be shown on the Course Discussion page.
This was the source of several bugs when trying to edit discussion threads.

This patch adds incrementing numbers to the title of each duplicate
subcategory when rendering the Course Discussion to make sure that
all of the threads are visible in Course Discussion.

lms/djangoapps/django_comment_client/tests/test_utils.py

@@ -359,6 +359,27 @@ class CategoryMapTestCase(CategoryMapTestMixin, ModuleStoreTestCase):
         self.course.cohort_config = {"cohorted": True}
         check_cohorted(True)
 
+    def test_tree_with_duplicate_targets(self):
+        self.create_discussion("Chapter 1", "Discussion A")
+        self.create_discussion("Chapter 1", "Discussion B")
+        self.create_discussion("Chapter 1", "Discussion A")  # duplicate
+        self.create_discussion("Chapter 1", "Discussion A")  # another duplicate
+        self.create_discussion("Chapter 2 / Section 1 / Subsection 1", "Discussion")
+        self.create_discussion("Chapter 2 / Section 1 / Subsection 1", "Discussion")  # duplicate
+
+        category_map = utils.get_discussion_category_map(self.course, self.user)
+
+        chapter1 = category_map["subcategories"]["Chapter 1"]
+        chapter1_discussions = set(["Discussion A", "Discussion B", "Discussion A (1)", "Discussion A (2)"])
+        self.assertEqual(set(chapter1["children"]), chapter1_discussions)
+        self.assertEqual(set(chapter1["entries"].keys()), chapter1_discussions)
+
+        chapter2 = category_map["subcategories"]["Chapter 2"]
+        subsection1 = chapter2["subcategories"]["Section 1"]["subcategories"]["Subsection 1"]
+        subsection1_discussions = set(["Discussion", "Discussion (1)"])
+        self.assertEqual(set(subsection1["children"]), subsection1_discussions)
+        self.assertEqual(set(subsection1["entries"].keys()), subsection1_discussions)
+
     def test_start_date_filter(self):
         now = datetime.now()
         later = datetime.max

lms/djangoapps/django_comment_client/utils.py

@@ -196,11 +196,18 @@ def get_discussion_category_map(course, user):
             if node[level]["start_date"] > category_start_date:
                 node[level]["start_date"] = category_start_date
 
+        dupe_counters = defaultdict(lambda: 0)  # counts the number of times we see each title
         for entry in entries:
-            node[level]["entries"][entry["title"]] = {"id": entry["id"],
-                                                      "sort_key": entry["sort_key"],
-                                                      "start_date": entry["start_date"],
-                                                      "is_cohorted": is_course_cohorted}
+            title = entry["title"]
+            if node[level]["entries"][title]:
+                # If we've already seen this title, append an incrementing number to disambiguate
+                # the category from other categores sharing the same title in the course discussion UI.
+                dupe_counters[title] += 1
+                title = u"{title} ({counter})".format(title=title, counter=dupe_counters[title])
+            node[level]["entries"][title] = {"id": entry["id"],
+                                             "sort_key": entry["sort_key"],
+                                             "start_date": entry["start_date"],
+                                             "is_cohorted": is_course_cohorted}
 
     # TODO.  BUG! : course location is not unique across multiple course runs!
     # (I think Kevin already noticed this)  Need to send course_id with requests, store it