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

@@ -337,6 +337,26 @@ def check_cohorted(is_cohorted):
         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)
+
+        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()

lms/djangoapps/django_comment_client/utils.py

@@ -183,11 +183,16 @@ def get_discussion_category_map(course):
             if node[level]["start_date"] > category_start_date:
                 node[level]["start_date"] = category_start_date
 
+        dupe_counters = defaultdict(lambda: 0)
         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]:
+                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