3 files changed, 29 insertions, 1 deletions
diff --git a/synapse/handlers/room_member.py b/synapse/handlers/room_member.py
index 06d09c2947..6cfee4b361 100644
--- a/synapse/handlers/room_member.py
+++ b/synapse/handlers/room_member.py
@@ -515,6 +515,15 @@ class RoomMemberHandler(object):
             yield self.store.set_room_is_public(old_room_id, False)
             yield self.store.set_room_is_public(room_id, True)
 
+        # Check if any groups we own contain the predecessor room
+        local_group_ids = yield self.store.get_local_groups_for_room(old_room_id)
+        for group_id in local_group_ids:
+            # Add new the new room to those groups
+            yield self.store.add_room_to_group(group_id, room_id, old_room["is_public"])
+
+            # Remove the old room from those groups
+            yield self.store.remove_room_from_group(group_id, old_room_id)
+
     @defer.inlineCallbacks
     def copy_user_state_on_room_upgrade(self, old_room_id, new_room_id, user_ids):
         """Copy user-specific information when they join a new room when that new room is the
diff --git a/synapse/storage/data_stores/main/group_server.py b/synapse/storage/data_stores/main/group_server.py
index b3a2771f1b..5ded539af8 100644
--- a/synapse/storage/data_stores/main/group_server.py
+++ b/synapse/storage/data_stores/main/group_server.py
@@ -553,6 +553,21 @@ class GroupServerStore(SQLBaseStore):
             desc="remove_user_from_summary",
         )
 
+    def get_local_groups_for_room(self, room_id):
+        """Get all of the local group that contain a given room
+        Args:
+            room_id (str): The ID of a room
+        Returns:
+            Deferred[list[str]]: A twisted.Deferred containing a list of group ids
+                containing this room
+        """
+        return self._simple_select_onecol(
+            table="group_rooms",
+            keyvalues={"room_id": room_id},
+            retcol="group_id",
+            desc="get_local_groups_for_room",
+        )
+
     def get_users_for_summary_by_role(self, group_id, include_private=False):
         """Get the users and roles that should be included in a summary request
 
diff --git a/synapse/storage/data_stores/main/state.py b/synapse/storage/data_stores/main/state.py
index 9e1541988e..5c293e0fa3 100644
--- a/synapse/storage/data_stores/main/state.py
+++ b/synapse/storage/data_stores/main/state.py
@@ -285,7 +285,11 @@ class StateGroupWorkerStore(
             room_id (str)
 
         Returns:
-            Deferred[unicode|None]: predecessor room id
+            Deferred[dict|None]: A dictionary containing the structure of the predecessor
+                field from the room's create event. The structure is subject to other servers,
+                but it is expected to be:
+                    * room_id (str): The room ID of the predecessor room
+                    * event_id (str): The ID of the tombstone event in the predecessor room
 
         Raises:
             NotFoundError if the room is unknown