Wait for lazy join to complete when getting current state (#12872)

synapse/storage/databases/main/state_deltas.py

@@ -27,7 +27,7 @@ class StateDeltasStore(SQLBaseStore):
     # attribute. TODO: can we get static analysis to enforce this?
     _curr_state_delta_stream_cache: StreamChangeCache
 
-    async def get_current_state_deltas(
+    async def get_partial_current_state_deltas(
         self, prev_stream_id: int, max_stream_id: int
     ) -> Tuple[int, List[Dict[str, Any]]]:
         """Fetch a list of room state changes since the given stream id
@@ -42,6 +42,8 @@ class StateDeltasStore(SQLBaseStore):
             - prev_event_id (str|None): previous event_id for this state key. None
                 if it's new state.
 
+        This may be the partial state if we're lazy joining the room.
+
         Args:
             prev_stream_id: point to get changes since (exclusive)
             max_stream_id: the point that we know has been correctly persisted