Add `is_encrypted` filtering to Sliding Sync `/sync` (#17281)

Based on [MSC3575](https://github.com/matrix-org/matrix-spec-proposals/pull/3575): Sliding Sync

1 files changed, 86 insertions, 1 deletions

diff --git a/synapse/storage/controllers/state.py b/synapse/storage/controllers/state.py
index f9eced23bf..cc9b162ae4 100644
--- a/synapse/storage/controllers/state.py
+++ b/synapse/storage/controllers/state.py
@@ -45,7 +45,7 @@ from synapse.storage.util.partial_state_events_tracker import (
     PartialStateEventsTracker,
 )
 from synapse.synapse_rust.acl import ServerAclEvaluator
-from synapse.types import MutableStateMap, StateMap, get_domain_from_id
+from synapse.types import MutableStateMap, StateMap, StreamToken, get_domain_from_id
 from synapse.types.state import StateFilter
 from synapse.util.async_helpers import Linearizer
 from synapse.util.caches import intern_string
@@ -372,6 +372,91 @@ class StateStorageController:
         )
         return state_map[event_id]
 
+    async def get_state_after_event(
+        self,
+        event_id: str,
+        state_filter: Optional[StateFilter] = None,
+        await_full_state: bool = True,
+    ) -> StateMap[str]:
+        """
+        Get the room state after the given event
+
+        Args:
+            event_id: event of interest
+            state_filter: The state filter used to fetch state from the database.
+            await_full_state: if `True`, will block if we do not yet have complete state
+                at the event and `state_filter` is not satisfied by partial state.
+                Defaults to `True`.
+        """
+        state_ids = await self.get_state_ids_for_event(
+            event_id,
+            state_filter=state_filter or StateFilter.all(),
+            await_full_state=await_full_state,
+        )
+
+        # using get_metadata_for_events here (instead of get_event) sidesteps an issue
+        # with redactions: if `event_id` is a redaction event, and we don't have the
+        # original (possibly because it got purged), get_event will refuse to return
+        # the redaction event, which isn't terribly helpful here.
+        #
+        # (To be fair, in that case we could assume it's *not* a state event, and
+        # therefore we don't need to worry about it. But still, it seems cleaner just
+        # to pull the metadata.)
+        m = (await self.stores.main.get_metadata_for_events([event_id]))[event_id]
+        if m.state_key is not None and m.rejection_reason is None:
+            state_ids = dict(state_ids)
+            state_ids[(m.event_type, m.state_key)] = event_id
+
+        return state_ids
+
+    async def get_state_at(
+        self,
+        room_id: str,
+        stream_position: StreamToken,
+        state_filter: Optional[StateFilter] = None,
+        await_full_state: bool = True,
+    ) -> StateMap[str]:
+        """Get the room state at a particular stream position
+
+        Args:
+            room_id: room for which to get state
+            stream_position: point at which to get state
+            state_filter: The state filter used to fetch state from the database.
+            await_full_state: if `True`, will block if we do not yet have complete state
+                at the last event in the room before `stream_position` and
+                `state_filter` is not satisfied by partial state. Defaults to `True`.
+        """
+        # FIXME: This gets the state at the latest event before the stream ordering,
+        # which might not be the same as the "current state" of the room at the time
+        # of the stream token if there were multiple forward extremities at the time.
+        last_event_id = (
+            await self.stores.main.get_last_event_id_in_room_before_stream_ordering(
+                room_id,
+                end_token=stream_position.room_key,
+            )
+        )
+
+        if last_event_id:
+            state = await self.get_state_after_event(
+                last_event_id,
+                state_filter=state_filter or StateFilter.all(),
+                await_full_state=await_full_state,
+            )
+
+        else:
+            # no events in this room - so presumably no state
+            state = {}
+
+            # (erikj) This should be rarely hit, but we've had some reports that
+            # we get more state down gappy syncs than we should, so let's add
+            # some logging.
+            logger.info(
+                "Failed to find any events in room %s at %s",
+                room_id,
+                stream_position.room_key,
+            )
+        return state
+
     @trace
     @tag_args
     async def get_state_for_groups(