Return the stable `event` field from `/send_join` per MSC3083. (#11413)

This does not remove the unstable field and still parses both.
Handling of the unstable field will need to be removed in the
future.

2 files changed, 16 insertions, 2 deletions

diff --git a/synapse/federation/federation_server.py b/synapse/federation/federation_server.py

index 9a8758e9a6..8fbc75aa65 100644
--- a/synapse/federation/federation_server.py
+++ b/synapse/federation/federation_server.py
@@ -613,8 +613,11 @@ class FederationServer(FederationBase):
         state = await self.store.get_events(state_ids)
 
         time_now = self._clock.time_msec()
+        event_json = event.get_pdu_json()
         return {
-            "org.matrix.msc3083.v2.event": event.get_pdu_json(),
+            # TODO Remove the unstable prefix when servers have updated.
+            "org.matrix.msc3083.v2.event": event_json,
+            "event": event_json,
             "state": [p.get_pdu_json(time_now) for p in state.values()],
             "auth_chain": [p.get_pdu_json(time_now) for p in auth_chain],
         }
diff --git a/synapse/federation/transport/client.py b/synapse/federation/transport/client.py

index 10b5aa5af8..0fea221165 100644
--- a/synapse/federation/transport/client.py
+++ b/synapse/federation/transport/client.py
@@ -1317,15 +1317,26 @@ class SendJoinParser(ByteParser[SendJoinResponse]):
             prefix + "auth_chain.item",
             use_float=True,
         )
-        self._coro_event = ijson.kvitems_coro(
+        # TODO Remove the unstable prefix when servers have updated.
+        #
+        # By re-using the same event dictionary this will cause the parsing of
+        # org.matrix.msc3083.v2.event and event to stomp over each other.
+        # Generally this should be fine.
+        self._coro_unstable_event = ijson.kvitems_coro(
             _event_parser(self._response.event_dict),
             prefix + "org.matrix.msc3083.v2.event",
             use_float=True,
         )
+        self._coro_event = ijson.kvitems_coro(
+            _event_parser(self._response.event_dict),
+            prefix + "event",
+            use_float=True,
+        )
 
     def write(self, data: bytes) -> int:
         self._coro_state.send(data)
         self._coro_auth.send(data)
+        self._coro_unstable_event.send(data)
         self._coro_event.send(data)
 
         return len(data)