Generalise _locally_reject_invite

changelog.d/8751.misc

@@ -0,0 +1 @@
+Generalise `RoomMemberHandler._locally_reject_invite` to apply to more flows than just invite.

synapse/handlers/room_member.py

@@ -1104,32 +1104,34 @@ async def remote_reject_invite(
             #
             logger.warning("Failed to reject invite: %s", e)
 
-            return await self._locally_reject_invite(
+            return await self._generate_local_out_of_band_leave(
                 invite_event, txn_id, requester, content
             )
 
-    async def _locally_reject_invite(
+    async def _generate_local_out_of_band_leave(
         self,
-        invite_event: EventBase,
+        previous_membership_event: EventBase,
         txn_id: Optional[str],
         requester: Requester,
         content: JsonDict,
     ) -> Tuple[str, int]:
-        """Generate a local invite rejection
+        """Generate a local leave event for a room
 
-        This is called after we fail to reject an invite via a remote server. It
-        generates an out-of-band membership event locally.
+        This can be called after we e.g fail to reject an invite via a remote server.
+        It generates an out-of-band membership event locally.
 
         Args:
-            invite_event: the invite to be rejected
+            previous_membership_event: the previous membership event for this user
             txn_id: optional transaction ID supplied by the client
-            requester:  user making the rejection request, according to the access token
-            content: additional content to include in the rejection event.
+            requester: user making the request, according to the access token
+            content: additional content to include in the leave event.
                Normally an empty dict.
-        """
 
-        room_id = invite_event.room_id
-        target_user = invite_event.state_key
+        Returns:
+            A tuple containing (event_id, stream_id of the leave event)
+        """
+        room_id = previous_membership_event.room_id
+        target_user = previous_membership_event.state_key
 
         content["membership"] = Membership.LEAVE
 
@@ -1141,12 +1143,12 @@ async def _locally_reject_invite(
             "state_key": target_user,
         }
 
-        # the auth events for the new event are the same as that of the invite, plus
-        # the invite itself.
+        # the auth events for the new event are the same as that of the previous event, plus
+        # the event itself.
         #
-        # the prev_events are just the invite.
-        prev_event_ids = [invite_event.event_id]
-        auth_event_ids = invite_event.auth_event_ids() + prev_event_ids
+        # the prev_events consist solely of the previous membership event.
+        prev_event_ids = [previous_membership_event.event_id]
+        auth_event_ids = previous_membership_event.auth_event_ids() + prev_event_ids
 
         event, context = await self.event_creation_handler.create_event(
             requester,