Implement MSC2175: remove the creator field from create events. (#15394)

3 files changed, 22 insertions, 12 deletions

diff --git a/synapse/handlers/federation_event.py b/synapse/handlers/federation_event.py
index 982c8d3b2f..8d5be81a92 100644
--- a/synapse/handlers/federation_event.py
+++ b/synapse/handlers/federation_event.py
@@ -1515,7 +1515,10 @@ class FederationEventHandler:
         # support it or the event is not from the room creator.
         room_version = await self._store.get_room_version(marker_event.room_id)
         create_event = await self._store.get_create_event_for_room(marker_event.room_id)
-        room_creator = create_event.content.get(EventContentFields.ROOM_CREATOR)
+        if not room_version.msc2175_implicit_room_creator:
+            room_creator = create_event.content.get(EventContentFields.ROOM_CREATOR)
+        else:
+            room_creator = create_event.sender
         if not room_version.msc2716_historical and (
             not self._config.experimental.msc2716_enabled
             or marker_event.sender != room_creator
diff --git a/synapse/handlers/message.py b/synapse/handlers/message.py
index 4c75433a63..a17fe3bf53 100644
--- a/synapse/handlers/message.py
+++ b/synapse/handlers/message.py
@@ -1909,7 +1909,12 @@ class EventCreationHandler:
                 room_version_obj = KNOWN_ROOM_VERSIONS[room_version]
 
                 create_event = await self.store.get_create_event_for_room(event.room_id)
-                room_creator = create_event.content.get(EventContentFields.ROOM_CREATOR)
+                if not room_version_obj.msc2175_implicit_room_creator:
+                    room_creator = create_event.content.get(
+                        EventContentFields.ROOM_CREATOR
+                    )
+                else:
+                    room_creator = create_event.sender
 
                 # Only check an insertion event if the room version
                 # supports it or the event is from the room creator.
diff --git a/synapse/handlers/room.py b/synapse/handlers/room.py
index be120cb12f..2d69cabf43 100644
--- a/synapse/handlers/room.py
+++ b/synapse/handlers/room.py
@@ -567,6 +567,7 @@ class RoomCreationHandler:
         await self._send_events_for_new_room(
             requester,
             new_room_id,
+            new_room_version,
             # we expect to override all the presets with initial_state, so this is
             # somewhat arbitrary.
             room_config={"preset": RoomCreationPreset.PRIVATE_CHAT},
@@ -922,6 +923,7 @@ class RoomCreationHandler:
         ) = await self._send_events_for_new_room(
             requester,
             room_id,
+            room_version,
             room_config=config,
             invite_list=invite_list,
             initial_state=initial_state,
@@ -998,6 +1000,7 @@ class RoomCreationHandler:
         self,
         creator: Requester,
         room_id: str,
+        room_version: RoomVersion,
         room_config: JsonDict,
         invite_list: List[str],
         initial_state: MutableStateMap,
@@ -1020,6 +1023,8 @@ class RoomCreationHandler:
                 the user requesting the room creation
             room_id:
                 room id for the room being created
+            room_version:
+                The room version of the new room.
             room_config:
                 A dict of configuration options. This will be the body of
                 a /createRoom request; see
@@ -1053,14 +1058,6 @@ class RoomCreationHandler:
         # (as this info can't be pulled from the db)
         state_map: MutableStateMap[str] = {}
 
-        def create_event_dict(etype: str, content: JsonDict, **kwargs: Any) -> JsonDict:
-            e = {"type": etype, "content": content}
-
-            e.update(event_keys)
-            e.update(kwargs)
-
-            return e
-
         async def create_event(
             etype: str,
             content: JsonDict,
@@ -1083,7 +1080,10 @@ class RoomCreationHandler:
             nonlocal depth
             nonlocal prev_event
 
-            event_dict = create_event_dict(etype, content, **kwargs)
+            # Create the event dictionary.
+            event_dict = {"type": etype, "content": content}
+            event_dict.update(event_keys)
+            event_dict.update(kwargs)
 
             (
                 new_event,
@@ -1120,7 +1120,9 @@ class RoomCreationHandler:
                 400, f"'{preset_config}' is not a valid preset", errcode=Codes.BAD_JSON
             )
 
-        creation_content.update({"creator": creator_id})
+        # MSC2175 removes the creator field from the create event.
+        if not room_version.msc2175_implicit_room_creator:
+            creation_content["creator"] = creator_id
         creation_event, unpersisted_creation_context = await create_event(
             EventTypes.Create, creation_content, False
         )