Refactor `create_new_client_event` to use a new parameter, `state_event_ids`, which accurately describes the usage with MSC2716 instead of abusing `auth_event_ids` (#12083)

Spawned from https://github.com/matrix-org/synapse/pull/10975#discussion_r813183430

Part of [MSC2716](https://github.com/matrix-org/matrix-spec-proposals/pull/2716)

1 files changed, 31 insertions, 0 deletions

diff --git a/synapse/handlers/room_member.py b/synapse/handlers/room_member.py
index 7cbc484b06..a33fa34aa8 100644
--- a/synapse/handlers/room_member.py
+++ b/synapse/handlers/room_member.py
@@ -272,6 +272,7 @@ class RoomMemberHandler(metaclass=abc.ABCMeta):
         allow_no_prev_events: bool = False,
         prev_event_ids: Optional[List[str]] = None,
         auth_event_ids: Optional[List[str]] = None,
+        state_event_ids: Optional[List[str]] = None,
         txn_id: Optional[str] = None,
         ratelimit: bool = True,
         content: Optional[dict] = None,
@@ -298,6 +299,14 @@ class RoomMemberHandler(metaclass=abc.ABCMeta):
                 The event ids to use as the auth_events for the new event.
                 Should normally be left as None, which will cause them to be calculated
                 based on the room state at the prev_events.
+            state_event_ids:
+                The full state at a given event. This is used particularly by the MSC2716
+                /batch_send endpoint. One use case is the historical `state_events_at_start`;
+                since each is marked as an `outlier`, the `EventContext.for_outlier()` won't
+                have any `state_ids` set and therefore can't derive any state even though the
+                prev_events are set so we need to set them ourself via this argument.
+                This should normally be left as None, which will cause the auth_event_ids
+                to be calculated based on the room state at the prev_events.
 
             txn_id:
             ratelimit:
@@ -353,6 +362,7 @@ class RoomMemberHandler(metaclass=abc.ABCMeta):
             allow_no_prev_events=allow_no_prev_events,
             prev_event_ids=prev_event_ids,
             auth_event_ids=auth_event_ids,
+            state_event_ids=state_event_ids,
             require_consent=require_consent,
             outlier=outlier,
             historical=historical,
@@ -456,6 +466,7 @@ class RoomMemberHandler(metaclass=abc.ABCMeta):
         allow_no_prev_events: bool = False,
         prev_event_ids: Optional[List[str]] = None,
         auth_event_ids: Optional[List[str]] = None,
+        state_event_ids: Optional[List[str]] = None,
     ) -> Tuple[str, int]:
         """Update a user's membership in a room.
 
@@ -487,6 +498,14 @@ class RoomMemberHandler(metaclass=abc.ABCMeta):
                 The event ids to use as the auth_events for the new event.
                 Should normally be left as None, which will cause them to be calculated
                 based on the room state at the prev_events.
+            state_event_ids:
+                The full state at a given event. This is used particularly by the MSC2716
+                /batch_send endpoint. One use case is the historical `state_events_at_start`;
+                since each is marked as an `outlier`, the `EventContext.for_outlier()` won't
+                have any `state_ids` set and therefore can't derive any state even though the
+                prev_events are set so we need to set them ourself via this argument.
+                This should normally be left as None, which will cause the auth_event_ids
+                to be calculated based on the room state at the prev_events.
 
         Returns:
             A tuple of the new event ID and stream ID.
@@ -526,6 +545,7 @@ class RoomMemberHandler(metaclass=abc.ABCMeta):
                     allow_no_prev_events=allow_no_prev_events,
                     prev_event_ids=prev_event_ids,
                     auth_event_ids=auth_event_ids,
+                    state_event_ids=state_event_ids,
                 )
 
         return result
@@ -548,6 +568,7 @@ class RoomMemberHandler(metaclass=abc.ABCMeta):
         allow_no_prev_events: bool = False,
         prev_event_ids: Optional[List[str]] = None,
         auth_event_ids: Optional[List[str]] = None,
+        state_event_ids: Optional[List[str]] = None,
     ) -> Tuple[str, int]:
         """Helper for update_membership.
 
@@ -581,6 +602,14 @@ class RoomMemberHandler(metaclass=abc.ABCMeta):
                 The event ids to use as the auth_events for the new event.
                 Should normally be left as None, which will cause them to be calculated
                 based on the room state at the prev_events.
+            state_event_ids:
+                The full state at a given event. This is used particularly by the MSC2716
+                /batch_send endpoint. One use case is the historical `state_events_at_start`;
+                since each is marked as an `outlier`, the `EventContext.for_outlier()` won't
+                have any `state_ids` set and therefore can't derive any state even though the
+                prev_events are set so we need to set them ourself via this argument.
+                This should normally be left as None, which will cause the auth_event_ids
+                to be calculated based on the room state at the prev_events.
 
         Returns:
             A tuple of the new event ID and stream ID.
@@ -708,6 +737,7 @@ class RoomMemberHandler(metaclass=abc.ABCMeta):
                 allow_no_prev_events=allow_no_prev_events,
                 prev_event_ids=prev_event_ids,
                 auth_event_ids=auth_event_ids,
+                state_event_ids=state_event_ids,
                 content=content,
                 require_consent=require_consent,
                 outlier=outlier,
@@ -932,6 +962,7 @@ class RoomMemberHandler(metaclass=abc.ABCMeta):
             ratelimit=ratelimit,
             prev_event_ids=latest_event_ids,
             auth_event_ids=auth_event_ids,
+            state_event_ids=state_event_ids,
             content=content,
             require_consent=require_consent,
             outlier=outlier,