Add a module API method to retrieve state from a room

synapse/module_api/__init__.py

@@ -867,15 +867,47 @@ async def get_user_ip_and_agents(
         else:
             return []
 
-    async def get_room_state(self, room_id: str) -> StateMap[EventBase]:
+    async def get_room_state(
+        self,
+        room_id: str,
+        event_filter: Optional[Iterable[Tuple[str, Optional[str]]]] = None,
+    ) -> StateMap[EventBase]:
         """Returns the current state of the given room.
 
         The events are returned as a mapping, in which the key for each event is a tuple
         which first element is the event's type and the second one is its state key.
 
         Added in Synapse v1.47.0
-        """
-        state_ids = await self._store.get_current_state_ids(room_id)
+
+        Args:
+            room_id: The ID of the room to get state from.
+            event_filter: A filter to apply when retrieving events. None if no filter
+                should be applied. If provided, must be an iterable of tuples. A tuple's
+                first element is the event type and the second is the state key, or is
+                None if the state key should not be filtered on.
+                An example of a filter is:
+                    [
+                        ("m.room.member", "@alice:example.com"),  # Member event for @alice:example.com
+                        ("org.matrix.some_event", ""),  # State event of type "org.matrix.some_event"
+                                                        # with an empty string as its state key
+                        ("org.matrix.some_other_event", None),  # State events of type "org.matrix.some_other_event"
+                                                                # regardless of their state key
+                    ]
+        """
+        if event_filter:
+            # If a filter was provided, turn it into a StateFilter and retrieve a filtered
+            # view of the state.
+            state_filter = StateFilter.from_types(event_filter)
+            state_ids = await self._store.get_filtered_current_state_ids(
+                room_id, state_filter,
+            )
+        else:
+            # If no filter was provided, get the whole state. We could also reuse the call
+            # to get_filtered_current_state_ids above, with `state_filter = StateFilter.all()`,
+            # but get_filtered_current_state_ids isn't cached and `get_current_state_ids`
+            # is, so using the latter when we can is better for perf.
+            state_ids = await self._store.get_current_state_ids(room_id)
+
         state_events = await self._store.get_events(state_ids.values())
 
         return {key: state_events[event_id] for key, event_id in state_ids.items()}