Fix a bug where redactions were not being sent over federation if we did not have the original event. (#13813)

synapse/storage/databases/main/events_worker.py

@@ -474,7 +474,7 @@ class EventsWorkerStore(SQLBaseStore):
             return []
 
         # there may be duplicates so we cast the list to a set
-        event_entry_map = await self._get_events_from_cache_or_db(
+        event_entry_map = await self.get_unredacted_events_from_cache_or_db(
             set(event_ids), allow_rejected=allow_rejected
         )
 
@@ -509,7 +509,9 @@ class EventsWorkerStore(SQLBaseStore):
                     continue
 
                 redacted_event_id = entry.event.redacts
-                event_map = await self._get_events_from_cache_or_db([redacted_event_id])
+                event_map = await self.get_unredacted_events_from_cache_or_db(
+                    [redacted_event_id]
+                )
                 original_event_entry = event_map.get(redacted_event_id)
                 if not original_event_entry:
                     # we don't have the redacted event (or it was rejected).
@@ -588,11 +590,16 @@ class EventsWorkerStore(SQLBaseStore):
         return events
 
     @cancellable
-    async def _get_events_from_cache_or_db(
-        self, event_ids: Iterable[str], allow_rejected: bool = False
+    async def get_unredacted_events_from_cache_or_db(
+        self,
+        event_ids: Iterable[str],
+        allow_rejected: bool = False,
     ) -> Dict[str, EventCacheEntry]:
         """Fetch a bunch of events from the cache or the database.
 
+        Note that the events pulled by this function will not have any redactions
+        applied, and no guarantee is made about the ordering of the events returned.
+
         If events are pulled from the database, they will be cached for future lookups.
 
         Unknown events are omitted from the response.