feat: add pre_delete signal to handle deletion of objects related to children blocks

Author: navinkarkera

xmodule/modulestore/__init__.py

@@ -1425,3 +1425,10 @@ def _emit_item_deleted_signal(self, usage_key, user_id):
         """
         if self.signal_handler:
             self.signal_handler.send("item_deleted", usage_key=usage_key, user_id=user_id)
+
+    def _emit_pre_item_deleted_signal(self, usage_key, user_id):
+        """
+        Helper method used to emit the item_deleted signal.
+        """
+        if self.signal_handler:
+            self.signal_handler.send("pre_item_deleted", usage_key=usage_key, user_id=user_id)

xmodule/modulestore/django.py

@@ -189,11 +189,19 @@ def do_my_expensive_update(course_key):
     course_deleted = SwitchedSignal("course_deleted")
     library_updated = SwitchedSignal("library_updated")
     item_deleted = SwitchedSignal("item_deleted")
+    pre_item_deleted = SwitchedSignal("pre_item_deleted")
 
     _mapping = {
         signal.name: signal
         for signal
-        in [pre_publish, course_published, course_deleted, library_updated, item_deleted]
+        in [
+            pre_publish,
+            course_published,
+            course_deleted,
+            library_updated,
+            item_deleted,
+            pre_item_deleted,
+        ]
     }
 
     def __init__(self, modulestore_class):

xmodule/modulestore/split_mongo/split.py

@@ -2523,6 +2523,8 @@ def delete_item(self, usage_locator, user_id, force=False):  # lint-amnesty, pyl
             # The supplied UsageKey is of the wrong type, so it can't possibly be stored in this modulestore.
             raise ItemNotFoundError(usage_locator)
 
+        self._emit_pre_item_deleted_signal(usage_locator, user_id)
+
         with self.bulk_operations(usage_locator.course_key):
             original_structure = self._lookup_course(usage_locator.course_key).structure
             block_key = BlockKey.from_usage_key(usage_locator)