Remove experimental configuration flags & unstable values for faster joins (#15625)

Synapse will no longer send (or respond to) the unstable flags
for faster joins. These were only available behind a configuration
flag and handled in parallel with the stable flags.

6 files changed, 8 insertions, 83 deletions

diff --git a/changelog.d/15625.misc b/changelog.d/15625.misc
new file mode 100644
index 0000000000..7ea8cc9433
--- /dev/null
+++ b/changelog.d/15625.misc
@@ -0,0 +1 @@
+Remove the unstable identifiers from faster joins ([MSC3706](https://github.com/matrix-org/matrix-spec-proposals/pull/3706).
diff --git a/synapse/config/experimental.py b/synapse/config/experimental.py
index 6e453bd963..d769b7f668 100644
--- a/synapse/config/experimental.py
+++ b/synapse/config/experimental.py
@@ -84,18 +84,6 @@ class ExperimentalConfig(Config):
             "msc3984_appservice_key_query", False
         )
 
-        # MSC3706 (server-side support for partial state in /send_join responses)
-        # Synapse will always serve partial state responses to requests using the stable
-        # query parameter `omit_members`. If this flag is set, Synapse will also serve
-        # partial state responses to requests using the unstable query parameter
-        # `org.matrix.msc3706.partial_state`.
-        self.msc3706_enabled: bool = experimental.get("msc3706_enabled", False)
-
-        # experimental support for faster joins over federation
-        # (MSC2775, MSC3706, MSC3895)
-        # requires a target server that can provide a partial join response (MSC3706)
-        self.faster_joins_enabled: bool = experimental.get("faster_joins", True)
-
         # MSC3720 (Account status endpoint)
         self.msc3720_enabled: bool = experimental.get("msc3720_enabled", False)
 
diff --git a/synapse/federation/federation_server.py b/synapse/federation/federation_server.py
index c590d8f96f..f4ca70a698 100644
--- a/synapse/federation/federation_server.py
+++ b/synapse/federation/federation_server.py
@@ -739,12 +739,10 @@ class FederationServer(FederationBase):
             "event": event_json,
             "state": [p.get_pdu_json(time_now) for p in state_events],
             "auth_chain": [p.get_pdu_json(time_now) for p in auth_chain_events],
-            "org.matrix.msc3706.partial_state": caller_supports_partial_state,
             "members_omitted": caller_supports_partial_state,
         }
 
         if servers_in_room is not None:
-            resp["org.matrix.msc3706.servers_in_room"] = list(servers_in_room)
             resp["servers_in_room"] = list(servers_in_room)
 
         return resp
diff --git a/synapse/federation/transport/client.py b/synapse/federation/transport/client.py
index d2fa9976da..1cfc4446c4 100644
--- a/synapse/federation/transport/client.py
+++ b/synapse/federation/transport/client.py
@@ -59,7 +59,6 @@ class TransportLayerClient:
 
     def __init__(self, hs: "HomeServer"):
         self.client = hs.get_federation_http_client()
-        self._faster_joins_enabled = hs.config.experimental.faster_joins_enabled
         self._is_mine_server_name = hs.is_mine_server_name
 
     async def get_room_state_ids(
@@ -363,12 +362,8 @@ class TransportLayerClient:
     ) -> "SendJoinResponse":
         path = _create_v2_path("/send_join/%s/%s", room_id, event_id)
         query_params: Dict[str, str] = {}
-        if self._faster_joins_enabled:
-            # lazy-load state on join
-            query_params["org.matrix.msc3706.partial_state"] = (
-                "true" if omit_members else "false"
-            )
-            query_params["omit_members"] = "true" if omit_members else "false"
+        # lazy-load state on join
+        query_params["omit_members"] = "true" if omit_members else "false"
 
         return await self.client.put_json(
             destination=destination,
@@ -902,9 +897,7 @@ def _members_omitted_parser(response: SendJoinResponse) -> Generator[None, Any,
     while True:
         val = yield
         if not isinstance(val, bool):
-            raise TypeError(
-                "members_omitted (formerly org.matrix.msc370c.partial_state) must be a boolean"
-            )
+            raise TypeError("members_omitted must be a boolean")
         response.members_omitted = val
 
 
@@ -967,27 +960,11 @@ class SendJoinParser(ByteParser[SendJoinResponse]):
             self._coros.append(
                 ijson.items_coro(
                     _members_omitted_parser(self._response),
-                    "org.matrix.msc3706.partial_state",
-                    use_float="True",
-                )
-            )
-            # The stable field name comes last, so it "wins" if the fields disagree
-            self._coros.append(
-                ijson.items_coro(
-                    _members_omitted_parser(self._response),
                     "members_omitted",
                     use_float="True",
                 )
             )
 
-            self._coros.append(
-                ijson.items_coro(
-                    _servers_in_room_parser(self._response),
-                    "org.matrix.msc3706.servers_in_room",
-                    use_float="True",
-                )
-            )
-
             # Again, stable field name comes last
             self._coros.append(
                 ijson.items_coro(
diff --git a/synapse/federation/transport/server/federation.py b/synapse/federation/transport/server/federation.py
index 36b0362504..3a744e25be 100644
--- a/synapse/federation/transport/server/federation.py
+++ b/synapse/federation/transport/server/federation.py
@@ -440,7 +440,6 @@ class FederationV2SendJoinServlet(BaseFederationServerServlet):
         server_name: str,
     ):
         super().__init__(hs, authenticator, ratelimiter, server_name)
-        self._read_msc3706_query_param = hs.config.experimental.msc3706_enabled
 
     async def on_PUT(
         self,
@@ -453,16 +452,7 @@ class FederationV2SendJoinServlet(BaseFederationServerServlet):
         # TODO(paul): assert that event_id parsed from path actually
         #   match those given in content
 
-        partial_state = False
-        # The stable query parameter wins, if it disagrees with the unstable
-        # parameter for some reason.
-        stable_param = parse_boolean_from_args(query, "omit_members", default=None)
-        if stable_param is not None:
-            partial_state = stable_param
-        elif self._read_msc3706_query_param:
-            partial_state = parse_boolean_from_args(
-                query, "org.matrix.msc3706.partial_state", default=False
-            )
+        partial_state = parse_boolean_from_args(query, "omit_members", default=False)
 
         result = await self.handler.on_send_join_request(
             origin, content, room_id, caller_supports_partial_state=partial_state
diff --git a/tests/federation/transport/test_client.py b/tests/federation/transport/test_client.py
index 3d61b1e8a9..93e5c85a27 100644
--- a/tests/federation/transport/test_client.py
+++ b/tests/federation/transport/test_client.py
@@ -86,18 +86,7 @@ class SendJoinParserTestCase(TestCase):
             return parsed_response.members_omitted
 
         self.assertTrue(parse({"members_omitted": True}))
-        self.assertTrue(parse({"org.matrix.msc3706.partial_state": True}))
-
         self.assertFalse(parse({"members_omitted": False}))
-        self.assertFalse(parse({"org.matrix.msc3706.partial_state": False}))
-
-        # If there's a conflict, the stable field wins.
-        self.assertTrue(
-            parse({"members_omitted": True, "org.matrix.msc3706.partial_state": False})
-        )
-        self.assertFalse(
-            parse({"members_omitted": False, "org.matrix.msc3706.partial_state": True})
-        )
 
     def test_servers_in_room(self) -> None:
         """Check that the servers_in_room field is correctly parsed"""
@@ -113,28 +102,10 @@ class SendJoinParserTestCase(TestCase):
             parsed_response = parser.finish()
             return parsed_response.servers_in_room
 
-        self.assertEqual(
-            parse({"org.matrix.msc3706.servers_in_room": ["hs1", "hs2"]}),
-            ["hs1", "hs2"],
-        )
         self.assertEqual(parse({"servers_in_room": ["example.com"]}), ["example.com"])
 
-        # If both are provided, the stable identifier should win
-        self.assertEqual(
-            parse(
-                {
-                    "org.matrix.msc3706.servers_in_room": ["old"],
-                    "servers_in_room": ["new"],
-                }
-            ),
-            ["new"],
-        )
-
-        # And lastly, we should be able to tell if neither field was present.
-        self.assertEqual(
-            parse({}),
-            None,
-        )
+        # We should be able to tell the field is not present.
+        self.assertEqual(parse({}), None)
 
     def test_errors_closing_coroutines(self) -> None:
         """Check we close all coroutines, even if closing the first raises an Exception.
@@ -143,7 +114,7 @@ class SendJoinParserTestCase(TestCase):
         assertions about its attributes or type.
         """
         parser = SendJoinParser(RoomVersions.V1, False)
-        response = {"org.matrix.msc3706.servers_in_room": ["hs1", "hs2"]}
+        response = {"servers_in_room": ["hs1", "hs2"]}
         serialisation = json.dumps(response).encode()
 
         # Mock the coroutines managed by this parser.