remote join processing: get create event from state, not auth_chain

changelog.d/12039.misc

@@ -0,0 +1 @@
+Preparation for faster-room-join work: when parsing the `send_join` response, get the `m.room.create` event from `state`, not `auth_chain`.

synapse/federation/federation_client.py

@@ -870,13 +870,15 @@ async def _execute(pdu: EventBase) -> None:
  for s in signed_state:
  s.internal_metadata = copy.deepcopy(s.internal_metadata)
 
- # double-check that the same create event has ended up in the auth chain
+ # double-check that the auth chain doesn't include a different create event
  auth_chain_create_events = [
  e.event_id
  for e in signed_auth
  if (e.type, e.state_key) == (EventTypes.Create, "")
  ]
- if auth_chain_create_events != [create_event.event_id]:
+ if auth_chain_create_events and auth_chain_create_events != [
+ create_event.event_id
+ ]:
  raise InvalidResponseError(
  "Unexpected create event(s) in auth chain: %s"
  % (auth_chain_create_events,)

synapse/handlers/federation.py

@@ -516,7 +516,7 @@ async def do_invite_join(
  await self.store.upsert_room_on_join(
  room_id=room_id,
  room_version=room_version_obj,
- auth_events=auth_chain,
+ state_events=state,
  )
 
  max_stream_id = await self._federation_event_handler.process_remote_join(

synapse/storage/databases/main/room.py

@@ -1498,7 +1498,7 @@ def __init__(
  self._event_reports_id_gen = IdGenerator(db_conn, "event_reports", "id")
 
  async def upsert_room_on_join(
- self, room_id: str, room_version: RoomVersion, auth_events: List[EventBase]
+ self, room_id: str, room_version: RoomVersion, state_events: List[EventBase]
  ) -> None:
  """Ensure that the room is stored in the table
 
@@ -1511,7 +1511,7 @@ async def upsert_room_on_join(
  has_auth_chain_index = await self.has_auth_chain_index(room_id)
 
  create_event = None
- for e in auth_events:
+ for e in state_events:
  if (e.type, e.state_key) == (EventTypes.Create, ""):
  create_event = e
  break