Merge remote-tracking branch 'upstream/release-v1.50'

synapse/handlers/message.py

@@ -21,7 +21,6 @@ from typing import TYPE_CHECKING, Any, Dict, List, Mapping, Optional, Tuple
 
 from canonicaljson import encode_canonical_json
 
-from twisted.internet import defer
 from twisted.internet.interfaces import IDelayedCall
 
 from synapse import event_auth
@@ -57,7 +56,7 @@ from synapse.storage.databases.main.events_worker import EventRedactBehaviour
 from synapse.storage.state import StateFilter
 from synapse.types import Requester, RoomAlias, StreamToken, UserID, create_requester
 from synapse.util import json_decoder, json_encoder, log_failure
-from synapse.util.async_helpers import Linearizer, unwrapFirstError
+from synapse.util.async_helpers import Linearizer, gather_results, unwrapFirstError
 from synapse.util.caches.expiringcache import ExpiringCache
 from synapse.util.metrics import measure_func
 from synapse.visibility import filter_events_for_client
@@ -498,6 +497,7 @@ class EventCreationHandler:
         require_consent: bool = True,
         outlier: bool = False,
         historical: bool = False,
+        allow_no_prev_events: bool = False,
         depth: Optional[int] = None,
     ) -> Tuple[EventBase, EventContext]:
         """
@@ -609,6 +609,7 @@ class EventCreationHandler:
             prev_event_ids=prev_event_ids,
             auth_event_ids=auth_event_ids,
             depth=depth,
+            allow_no_prev_events=allow_no_prev_events,
         )
 
         # In an ideal world we wouldn't need the second part of this condition. However,
@@ -884,6 +885,7 @@ class EventCreationHandler:
         prev_event_ids: Optional[List[str]] = None,
         auth_event_ids: Optional[List[str]] = None,
         depth: Optional[int] = None,
+        allow_no_prev_events: bool = False,
     ) -> Tuple[EventBase, EventContext]:
         """Create a new event for a local client
 
@@ -914,6 +916,7 @@ class EventCreationHandler:
         full_state_ids_at_event = None
         if auth_event_ids is not None:
             # If auth events are provided, prev events must be also.
+            # prev_event_ids could be an empty array though.
             assert prev_event_ids is not None
 
             # Copy the full auth state before it stripped down
@@ -945,14 +948,22 @@ class EventCreationHandler:
         else:
             prev_event_ids = await self.store.get_prev_events_for_room(builder.room_id)
 
-        # we now ought to have some prev_events (unless it's a create event).
-        #
-        # do a quick sanity check here, rather than waiting until we've created the
+        # Do a quick sanity check here, rather than waiting until we've created the
         # event and then try to auth it (which fails with a somewhat confusing "No
         # create event in auth events")
-        assert (
-            builder.type == EventTypes.Create or len(prev_event_ids) > 0
-        ), "Attempting to create an event with no prev_events"
+        if allow_no_prev_events:
+            # We allow events with no `prev_events` but it better have some `auth_events`
+            assert (
+                builder.type == EventTypes.Create
+                # Allow an event to have empty list of prev_event_ids
+                # only if it has auth_event_ids.
+                or auth_event_ids
+            ), "Attempting to create a non-m.room.create event with no prev_events or auth_event_ids"
+        else:
+            # we now ought to have some prev_events (unless it's a create event).
+            assert (
+                builder.type == EventTypes.Create or prev_event_ids
+            ), "Attempting to create a non-m.room.create event with no prev_events"
 
         event = await builder.build(
             prev_event_ids=prev_event_ids,
@@ -1158,9 +1169,9 @@ class EventCreationHandler:
 
         # We now persist the event (and update the cache in parallel, since we
         # don't want to block on it).
-        result = await make_deferred_yieldable(
-            defer.gatherResults(
-                [
+        result, _ = await make_deferred_yieldable(
+            gather_results(
+                (
                     run_in_background(
                         self._persist_event,
                         requester=requester,
@@ -1172,12 +1183,12 @@ class EventCreationHandler:
                     run_in_background(
                         self.cache_joined_hosts_for_event, event, context
                     ).addErrback(log_failure, "cache_joined_hosts_for_event failed"),
-                ],
+                ),
                 consumeErrors=True,
             )
         ).addErrback(unwrapFirstError)
 
-        return result[0]
+        return result
 
     async def _persist_event(
         self,