Faster joins: don't stall when a user joins during a fast join (#14606)

Fixes #12801.
Complement tests are at
https://github.com/matrix-org/complement/pull/567.

Avoid blocking on full state when handling a subsequent join into a
partial state room.

Also always perform a remote join into partial state rooms, since we do
not know whether the joining user has been banned and want to avoid
leaking history to banned users.

Signed-off-by: Mathieu Velten <mathieuv@matrix.org>
Co-authored-by: Sean Quah <seanq@matrix.org>
Co-authored-by: David Robertson <davidr@element.io>

1 files changed, 1 insertions, 1 deletions

diff --git a/synapse/handlers/federation.py b/synapse/handlers/federation.py

index 43ed4a3dd1..08727e4857 100644
--- a/synapse/handlers/federation.py
+++ b/synapse/handlers/federation.py
@@ -49,6 +49,7 @@ from synapse.api.errors import (
     FederationPullAttemptBackoffError,
     HttpResponseException,
     NotFoundError,
+    PartialStateConflictError,
     RequestSendFailed,
     SynapseError,
 )
@@ -68,7 +69,6 @@ from synapse.replication.http.federation import (
     ReplicationCleanRoomRestServlet,
     ReplicationStoreRoomOnOutlierMembershipRestServlet,
 )
-from synapse.storage.databases.main.events import PartialStateConflictError
 from synapse.storage.databases.main.events_worker import EventRedactBehaviour
 from synapse.types import JsonDict, StrCollection, get_domain_from_id
 from synapse.types.state import StateFilter