Review comments

changelog.d/19424.feature

@@ -1 +1 @@
-Add experimental support for MSC4242: State DAGs. Excludes federation support.
+Add experimental support for [MSC4242](https://github.com/matrix-org/matrix-spec-proposals/pull/4242): State DAGs. Excludes federation support.

rust/src/events/internal_metadata.rs

@@ -60,7 +60,7 @@ enum EventInternalMetadataData {
     DelayId(Box<str>),
     TokenId(i64),
     DeviceId(Box<str>),
-    CalculatedAuthEventIDs(Vec<String>),
+    CalculatedAuthEventIDs(Vec<String>), // MSC4242: State DAGs
 }
 
 impl EventInternalMetadataData {

synapse/handlers/room_member.py

@@ -2141,8 +2141,9 @@ class RoomMemberMasterHandler(RoomMemberHandler):
                 list(previous_membership_event.auth_event_ids()) + prev_event_ids
             )
 
-        # Either one is set or the other
-        assert prev_state_events or auth_event_ids
+        # State DAG rooms should not have auth events specified
+        if prev_state_events:
+            assert auth_event_ids is None
         # Try several times, it could fail with PartialStateConflictError
         # in handle_new_client_event, cf comment in except block.
         max_retries = 5

synapse/storage/schema/main/delta/94/03_state_dag_fwd_extrems.sql

@@ -34,8 +34,5 @@ CREATE TABLE IF NOT EXISTS msc4242_state_dag_edges(
     -- one of the `prev_state_events` for this event ID. We must have it since we must have the entire state DAG.
     -- can be NULL for the create event.
     prev_state_event_id TEXT REFERENCES events(event_id)
-    -- calculated depth for this event ID. There is some denormalisation here as we're storing the depth
-    -- multiple times for each prev_state_event_id.
-    -- depth BIGINT NOT NULL
 );
 CREATE UNIQUE INDEX msc4242_state_dag_edges_key ON msc4242_state_dag_edges(room_id, event_id, prev_state_event_id);