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.

5 files changed, 19 insertions, 4 deletions

diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml

index 8d7e8cafd9..3bee4ee9f3 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -374,7 +374,7 @@ jobs:
         working-directory: complement/dockerfiles
 
       # Run Complement
-      - run: go test -v -tags synapse_blacklist,msc2403,msc2946,msc3083 ./tests/...
+      - run: go test -v -tags synapse_blacklist,msc2403,msc2946 ./tests/...
         env:
           COMPLEMENT_BASE_IMAGE: complement-synapse:latest
         working-directory: complement
diff --git a/changelog.d/11413.bugfix b/changelog.d/11413.bugfix
new file mode 100644

index 0000000000..44111d8152
--- /dev/null
+++ b/changelog.d/11413.bugfix
@@ -0,0 +1 @@
+The `/send_join` response now includes the stable `event` field instead of the unstable field from [MSC3083](https://github.com/matrix-org/matrix-doc/pull/3083).
diff --git a/scripts-dev/complement.sh b/scripts-dev/complement.sh

index 29568eded8..972244f4c9 100755
--- a/scripts-dev/complement.sh
+++ b/scripts-dev/complement.sh
@@ -65,4 +65,4 @@ if [[ -n "$1" ]]; then
 fi
 
 # Run the tests!
-go test -v -tags synapse_blacklist,msc2946,msc3083,msc2403 -count=1 $EXTRA_COMPLEMENT_ARGS ./tests/...
+go test -v -tags synapse_blacklist,msc2946,msc2403 -count=1 $EXTRA_COMPLEMENT_ARGS ./tests/...
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)