From 8533c8b03d8916e3805c7d0e0020226017680147 Mon Sep 17 00:00:00 2001
From: Richard van der Hoff <1389908+richvdh@users.noreply.github.com>
Date: Thu, 3 Mar 2022 19:58:08 +0000
Subject: [PATCH] Avoid generating state groups for local out-of-band leaves
 (#12154)

If we locally generate a rejection for an invite received over federation, it
is stored as an outlier (because we probably don't have the state for the
room). However, currently we still generate a state group for it (even though
the state in that state group will be nonsense).

By setting the `outlier` param on `create_event`, we avoid the nonsensical
state.
---
 changelog.d/12154.misc          | 1 +
 synapse/handlers/room_member.py | 2 +-
 2 files changed, 2 insertions(+), 1 deletion(-)
 create mode 100644 changelog.d/12154.misc

diff --git a/changelog.d/12154.misc b/changelog.d/12154.misc
new file mode 100644
index 000000000..18d2a4728
--- /dev/null
+++ b/changelog.d/12154.misc
@@ -0,0 +1 @@
+Avoid generating state groups for local out-of-band leaves.
diff --git a/synapse/handlers/room_member.py b/synapse/handlers/room_member.py
index a582837cf..7cbc484b0 100644
--- a/synapse/handlers/room_member.py
+++ b/synapse/handlers/room_member.py
@@ -1736,8 +1736,8 @@ class RoomMemberMasterHandler(RoomMemberHandler):
             txn_id=txn_id,
             prev_event_ids=prev_event_ids,
             auth_event_ids=auth_event_ids,
+            outlier=True,
         )
-        event.internal_metadata.outlier = True
         event.internal_metadata.out_of_band_membership = True
 
         result_event = await self.event_creation_handler.handle_new_client_event(