Add in "previous_count" and "max_count"

common/lib/xmodule/xmodule/library_content_module.py

@@ -221,35 +221,39 @@ class LibraryContentModule(LibraryContentFields, XModule, StudioEditableModule):
             # Already done:
             return self._selected_set  # pylint: disable=access-member-before-definition
 
+        selected = set(tuple(k) for k in self.selected)  # set of (block_type, block_id) tuples assigned to this student
+        previous_count = len(selected)
+
         lib_tools = self.runtime.service(self, 'library_tools')
         format_block_keys = lambda keys: lib_tools.create_block_analytics_summary(self.location.course_key, keys)
 
+        def publish_event(event_name, **kwargs):
+            """ Publish an event for analytics purposes """
+            event_data = {
+                "location": unicode(self.location),
+                "result": format_block_keys(selected),
+                "previous_count": previous_count,
+                "max_count": self.max_count,
+            }
+            event_data.update(kwargs)
+            self.runtime.publish(self, "edx.librarycontentblock.content.{}".format(event_name), event_data)
+
         # Determine which of our children we will show:
-        selected = set(tuple(k) for k in self.selected)  # set of (block_type, block_id) tuples
         valid_block_keys = set([(c.block_type, c.block_id) for c in self.children])  # pylint: disable=no-member
         # Remove any selected blocks that are no longer valid:
         invalid_block_keys = (selected - valid_block_keys)
         if invalid_block_keys:
             selected -= invalid_block_keys
             # Publish an event for analytics purposes:
-            self.runtime.publish(self, "edx.librarycontentblock.content.removed", {
-                "location": unicode(self.location),
-                "removed": format_block_keys(invalid_block_keys),
-                "reason": "invalid",  # Deleted from library or library being used has changed
-                "result": format_block_keys(selected),
-            })
+            # reason "invalid" means deleted from library or a different library is now being used.
+            publish_event("removed", removed=format_block_keys(invalid_block_keys), reason="invalid")
         # If max_count has been decreased, we may have to drop some previously selected blocks:
         overlimit_block_keys = set()
         while len(selected) > self.max_count:
             overlimit_block_keys.add(selected.pop())
         if overlimit_block_keys:
             # Publish an event for analytics purposes:
-            self.runtime.publish(self, "edx.librarycontentblock.content.removed", {
-                "location": unicode(self.location),
-                "removed": format_block_keys(overlimit_block_keys),
-                "reason": "overlimit",
-                "result": format_block_keys(selected),
-            })
+            publish_event("removed", removed=format_block_keys(overlimit_block_keys), reason="overlimit")
         # Do we have enough blocks now?
         num_to_add = self.max_count - len(selected)
         if num_to_add > 0:
@@ -265,11 +269,7 @@ class LibraryContentModule(LibraryContentFields, XModule, StudioEditableModule):
             selected |= added_block_keys
             if added_block_keys:
                 # Publish an event for analytics purposes:
-                self.runtime.publish(self, "edx.librarycontentblock.content.assigned", {
-                    "location": unicode(self.location),
-                    "added": format_block_keys(added_block_keys),
-                    "result": format_block_keys(selected),
-                })
+                publish_event("assigned", added=format_block_keys(added_block_keys))
         # Save our selections to the user state, to ensure consistency:
         self.selected = list(selected)  # TODO: this doesn't save from the LMS "Progress" page.
         # Cache the results

common/lib/xmodule/xmodule/tests/test_library_content.py

@@ -351,6 +351,8 @@ class TestLibraryContentAnalytics(LibraryContentTest):
             "location": unicode(self.lc_block.location),
             "added": [block_info],
             "result": [block_info],
+            "previous_count": 0,
+            "max_count": 1,
         })
         self.publisher.reset_mock()
 
@@ -364,6 +366,8 @@ class TestLibraryContentAnalytics(LibraryContentTest):
         event_data = self._assert_event_was_published("assigned")
         self.assertEqual(event_data["added"][0]["usage_key"], unicode(new_child.location))
         self.assertEqual(len(event_data["result"]), 2)
+        self.assertEqual(event_data["previous_count"], 1)
+        self.assertEqual(event_data["max_count"], 2)
 
     def test_assigned_descendants(self):
         """