Connect historical state chain to event chain github/madlittlemods/no-more-floating-msc2716-batches madlittlemods/no-more-floating-msc2716-batches

2 files changed, 18 insertions, 38 deletions

diff --git a/synapse/handlers/room_batch.py b/synapse/handlers/room_batch.py
index 1572ea8209..1b87f09903 100644
--- a/synapse/handlers/room_batch.py
+++ b/synapse/handlers/room_batch.py
@@ -239,7 +239,7 @@ class RoomBatchHandler:
         events_to_create: List[JsonDict],
         room_id: str,
         inherited_depth: int,
-        initial_state_event_ids: List[str],
+        state_chain_event_id_to_connect_to: str,
         app_service_requester: Requester,
     ) -> List[str]:
         """Create and persists all events provided sequentially. Handles the
@@ -255,10 +255,7 @@ class RoomBatchHandler:
             room_id: Room where you want the events persisted in.
             inherited_depth: The depth to create the events at (you will
                 probably by calling inherit_depth_from_prev_ids(...)).
-            initial_state_event_ids:
-                This is used to set explicit state for the insertion event at
-                the start of the historical batch since it's floating with no
-                prev_events to derive state from automatically.
+            state_chain_event_id_to_connect_to: TODO: HERE
             app_service_requester: The requester of an application service.
 
         Returns:
@@ -271,10 +268,8 @@ class RoomBatchHandler:
         # We expect the last event in a historical batch to be an batch event
         assert events_to_create[-1]["type"] == EventTypes.MSC2716_BATCH
 
-        # Make the historical event chain float off on its own by specifying no
-        # prev_events for the first event in the chain which causes the HS to
-        # ask for the state at the start of the batch later.
-        prev_event_ids: List[str] = []
+        # Connect the historical event chain to the state chain
+        prev_event_ids: List[str] = [state_chain_event_id_to_connect_to]
 
         event_ids = []
         events_to_persist = []
@@ -302,16 +297,7 @@ class RoomBatchHandler:
                     ev["sender"], app_service_requester.app_service
                 ),
                 event_dict,
-                # Only the first event (which is the insertion event) in the
-                # chain should be floating. The rest should hang off each other
-                # in a chain.
-                allow_no_prev_events=index == 0,
                 prev_event_ids=event_dict.get("prev_events"),
-                # Since the first event (which is the insertion event) in the
-                # chain is floating with no `prev_events`, it can't derive state
-                # from anywhere automatically. So we need to set some state
-                # explicitly.
-                state_event_ids=initial_state_event_ids if index == 0 else None,
                 historical=True,
                 depth=inherited_depth,
             )
@@ -360,7 +346,7 @@ class RoomBatchHandler:
         room_id: str,
         batch_id_to_connect_to: str,
         inherited_depth: int,
-        initial_state_event_ids: List[str],
+        state_chain_event_id_to_connect_to: str,
         app_service_requester: Requester,
     ) -> Tuple[List[str], str]:
         """
@@ -375,13 +361,7 @@ class RoomBatchHandler:
                 want this batch to connect to.
             inherited_depth: The depth to create the events at (you will
                 probably by calling inherit_depth_from_prev_ids(...)).
-            initial_state_event_ids:
-                This is used to set explicit state for the insertion event at
-                the start of the historical batch since it's floating with no
-                prev_events to derive state from automatically. This should
-                probably be the state from the `prev_event` defined by
-                `/batch_send?prev_event_id=$abc` plus the outcome of
-                `persist_state_events_at_start`
+            state_chain_event_id_to_connect_to: TODO: HERE
             app_service_requester: The requester of an application service.
 
         Returns:
@@ -427,7 +407,7 @@ class RoomBatchHandler:
             events_to_create=events_to_create,
             room_id=room_id,
             inherited_depth=inherited_depth,
-            initial_state_event_ids=initial_state_event_ids,
+            state_chain_event_id_to_connect_to=state_chain_event_id_to_connect_to,
             app_service_requester=app_service_requester,
         )
 
diff --git a/synapse/rest/client/room_batch.py b/synapse/rest/client/room_batch.py
index 3c865431f1..496c8bc567 100644
--- a/synapse/rest/client/room_batch.py
+++ b/synapse/rest/client/room_batch.py
@@ -145,17 +145,16 @@ class RoomBatchSendEventRestServlet(RestServlet):
         )
 
         state_event_ids_at_start = []
-        # Create and persist all of the state events that float off on their own
-        # before the batch. These will most likely be all of the invite/member
-        # state events used to auth the upcoming historical messages.
+        # Create and persist all of the state events in a chain before the
+        # batch. These will most likely be all of the invite/member state events
+        # used to auth the upcoming historical messages.
         if body["state_events_at_start"]:
-            state_event_ids_at_start = (
-                await self.room_batch_handler.persist_state_events_at_start(
-                    state_events_at_start=body["state_events_at_start"],
-                    room_id=room_id,
-                    initial_prev_event_ids=prev_event_ids_from_query,
-                    app_service_requester=requester,
-                )
+            state_event_ids_at_start = await self.room_batch_handler.persist_state_events_at_start(
+                state_events_at_start=body["state_events_at_start"],
+                room_id=room_id,
+                # Connect the state chain to prev_event we're inserting next to
+                initial_prev_event_ids=prev_event_ids_from_query,
+                app_service_requester=requester,
             )
             # Update our ongoing auth event ID list with all of the new state we
             # just created
@@ -222,7 +221,8 @@ class RoomBatchSendEventRestServlet(RestServlet):
             room_id=room_id,
             batch_id_to_connect_to=batch_id_to_connect_to,
             inherited_depth=inherited_depth,
-            initial_state_event_ids=state_event_ids,
+            # Connect the historical batch to the state chain
+            state_chain_event_id_to_connect_to=state_event_ids_at_start[-1],
             app_service_requester=requester,
         )