Add support for MSC4115 (#17104)

Co-authored-by: Andrew Morgan <[email protected]>

Author: richvdh

changelog.d/17104.feature

@@ -0,0 +1 @@
+Add support for MSC4115 (membership metadata on events).

docker/complement/conf/workers-shared-extra.yaml.j2

@@ -92,8 +92,6 @@ allow_device_name_lookup_over_federation: true
 ## Experimental Features ##
 
 experimental_features:
-  # client-side support for partial state in /send_join responses
-  faster_joins: true
   # Enable support for polls
   msc3381_polls_enabled: true
   # Enable deleting device-specific notification settings stored in account data
@@ -105,6 +103,8 @@ experimental_features:
   # no UIA for x-signing upload for the first time
   msc3967_enabled: true
 
+  msc4115_membership_on_events: true
+
 server_notices:
   system_mxid_localpart: _server
   system_mxid_display_name: "Server Alert"

rust/src/events/internal_metadata.rs

@@ -20,8 +20,10 @@
 
 //! Implements the internal metadata class attached to events.
 //!
-//! The internal metadata is a bit like a `TypedDict`, in that it is stored as a
-//! JSON dict in the DB. Most events have zero, or only a few, of these keys
+//! The internal metadata is a bit like a `TypedDict`, in that most of
+//! it is stored as a JSON dict in the DB (the exceptions being `outlier`
+//! and `stream_ordering` which have their own columns in the database).
+//! Most events have zero, or only a few, of these keys
 //! set. Therefore, since we care more about memory size than performance here,
 //! we store these fields in a mapping.
 //!
@@ -234,6 +236,9 @@ impl EventInternalMetadata {
         self.clone()
     }
 
+    /// Get a dict holding the data stored in the `internal_metadata` column in the database.
+    ///
+    /// Note that `outlier` and `stream_ordering` are stored in separate columns so are not returned here.
     fn get_dict(&self, py: Python<'_>) -> PyResult<PyObject> {
         let dict = PyDict::new(py);
 

synapse/api/constants.py

@@ -234,6 +234,13 @@ class EventContentFields:
     TO_DEVICE_MSGID: Final = "org.matrix.msgid"
 
 
+class EventUnsignedContentFields:
+    """Fields found inside the 'unsigned' data on events"""
+
+    # Requesting user's membership, per MSC4115
+    MSC4115_MEMBERSHIP: Final = "io.element.msc4115.membership"
+
+
 class RoomTypes:
     """Understood values of the room_type field of m.room.create events."""
 

synapse/config/experimental.py

@@ -432,3 +432,7 @@ def read_config(self, config: JsonDict, **kwargs: Any) -> None:
                 "You cannot have MSC4108 both enabled and delegated at the same time",
                 ("experimental", "msc4108_delegation_endpoint"),
             )
+
+        self.msc4115_membership_on_events = experimental.get(
+            "msc4115_membership_on_events", False
+        )

synapse/events/utils.py

@@ -49,7 +49,7 @@
 from synapse.api.room_versions import RoomVersion
 from synapse.types import JsonDict, Requester
 
-from . import EventBase
+from . import EventBase, make_event_from_dict
 
 if TYPE_CHECKING:
     from synapse.handlers.relations import BundledAggregations
@@ -82,17 +82,14 @@ def prune_event(event: EventBase) -> EventBase:
     """
     pruned_event_dict = prune_event_dict(event.room_version, event.get_dict())
 
-    from . import make_event_from_dict
-
     pruned_event = make_event_from_dict(
         pruned_event_dict, event.room_version, event.internal_metadata.get_dict()
     )
 
-    # copy the internal fields
+    # Copy the bits of `internal_metadata` that aren't returned by `get_dict`
     pruned_event.internal_metadata.stream_ordering = (
         event.internal_metadata.stream_ordering
     )
-
     pruned_event.internal_metadata.outlier = event.internal_metadata.outlier
 
     # Mark the event as redacted
@@ -101,6 +98,29 @@ def prune_event(event: EventBase) -> EventBase:
     return pruned_event
 
 
+def clone_event(event: EventBase) -> EventBase:
+    """Take a copy of the event.
+
+    This is mostly useful because it does a *shallow* copy of the `unsigned` data,
+    which means it can then be updated without corrupting the in-memory cache. Note that
+    other properties of the event, such as `content`, are *not* (currently) copied here.
+    """
+    # XXX: We rely on at least one of `event.get_dict()` and `make_event_from_dict()`
+    #   making a copy of `unsigned`. Currently, both do, though I don't really know why.
+    #   Still, as long as they do, there's not much point doing yet another copy here.
+    new_event = make_event_from_dict(
+        event.get_dict(), event.room_version, event.internal_metadata.get_dict()
+    )
+
+    # Copy the bits of `internal_metadata` that aren't returned by `get_dict`.
+    new_event.internal_metadata.stream_ordering = (
+        event.internal_metadata.stream_ordering
+    )
+    new_event.internal_metadata.outlier = event.internal_metadata.outlier
+
+    return new_event
+
+
 def prune_event_dict(room_version: RoomVersion, event_dict: JsonDict) -> JsonDict:
     """Redacts the event_dict in the same way as `prune_event`, except it
     operates on dicts rather than event objects

synapse/handlers/admin.py

@@ -42,6 +42,7 @@ def __init__(self, hs: "HomeServer"):
         self._device_handler = hs.get_device_handler()
         self._storage_controllers = hs.get_storage_controllers()
         self._state_storage_controller = self._storage_controllers.state
+        self._hs_config = hs.config
         self._msc3866_enabled = hs.config.experimental.msc3866.enabled
 
     async def get_whois(self, user: UserID) -> JsonMapping:
@@ -217,7 +218,10 @@ async def export_user_data(self, user_id: str, writer: "ExfiltrationWriter") ->
                 )
 
                 events = await filter_events_for_client(
-                    self._storage_controllers, user_id, events
+                    self._storage_controllers,
+                    user_id,
+                    events,
+                    msc4115_membership_on_events=self._hs_config.experimental.msc4115_membership_on_events,
                 )
 
                 writer.write_events(room_id, events)

synapse/handlers/events.py

@@ -148,6 +148,7 @@ class EventHandler:
     def __init__(self, hs: "HomeServer"):
         self.store = hs.get_datastores().main
         self._storage_controllers = hs.get_storage_controllers()
+        self._config = hs.config
 
     async def get_event(
         self,
@@ -189,7 +190,11 @@ async def get_event(
         is_peeking = not is_user_in_room
 
         filtered = await filter_events_for_client(
-            self._storage_controllers, user.to_string(), [event], is_peeking=is_peeking
+            self._storage_controllers,
+            user.to_string(),
+            [event],
+            is_peeking=is_peeking,
+            msc4115_membership_on_events=self._config.experimental.msc4115_membership_on_events,
         )
 
         if not filtered:

synapse/handlers/initial_sync.py

@@ -221,7 +221,10 @@ async def handle_room(event: RoomsForUser) -> None:
                 ).addErrback(unwrapFirstError)
 
                 messages = await filter_events_for_client(
-                    self._storage_controllers, user_id, messages
+                    self._storage_controllers,
+                    user_id,
+                    messages,
+                    msc4115_membership_on_events=self.hs.config.experimental.msc4115_membership_on_events,
                 )
 
                 start_token = now_token.copy_and_replace(StreamKeyType.ROOM, token)
@@ -380,6 +383,7 @@ async def _room_initial_sync_parted(
             requester.user.to_string(),
             messages,
             is_peeking=is_peeking,
+            msc4115_membership_on_events=self.hs.config.experimental.msc4115_membership_on_events,
         )
 
         start_token = StreamToken.START.copy_and_replace(StreamKeyType.ROOM, token)
@@ -494,6 +498,7 @@ async def get_receipts() -> List[JsonMapping]:
             requester.user.to_string(),
             messages,
             is_peeking=is_peeking,
+            msc4115_membership_on_events=self.hs.config.experimental.msc4115_membership_on_events,
         )
 
         start_token = now_token.copy_and_replace(StreamKeyType.ROOM, token)

synapse/handlers/pagination.py

@@ -623,6 +623,7 @@ async def get_messages(
                 user_id,
                 events,
                 is_peeking=(member_event_id is None),
+                msc4115_membership_on_events=self.hs.config.experimental.msc4115_membership_on_events,
             )
 
         # if after the filter applied there are no more events