Fix MSC4222 returning full state (#17915)

There was a bug that meant we would return the full state of the room on
incremental syncs when using lazy loaded members and there were no
entries in the timeline.

This was due to trying to use `state_filter or state_filter.all()` as a
short hand for handling `None` case, however `state_filter` implements
`__bool__` so if the state filter was empty it would be set to full.

c.f. MSC4222 and #17888

1 files changed, 36 insertions, 20 deletions

diff --git a/synapse/storage/controllers/state.py b/synapse/storage/controllers/state.py

index b50eb8868e..f28f5d7e03 100644
--- a/synapse/storage/controllers/state.py
+++ b/synapse/storage/controllers/state.py
@@ -234,8 +234,11 @@ class StateStorageController:
             RuntimeError if we don't have a state group for one or more of the events
                (ie they are outliers or unknown)
         """
+        if state_filter is None:
+            state_filter = StateFilter.all()
+
         await_full_state = True
-        if state_filter and not state_filter.must_await_full_state(self._is_mine_id):
+        if not state_filter.must_await_full_state(self._is_mine_id):
             await_full_state = False
 
         event_to_groups = await self.get_state_group_for_events(
@@ -244,7 +247,7 @@ class StateStorageController:
 
         groups = set(event_to_groups.values())
         group_to_state = await self.stores.state._get_state_for_groups(
-            groups, state_filter or StateFilter.all()
+            groups, state_filter
         )
 
         state_event_map = await self.stores.main.get_events(
@@ -292,10 +295,11 @@ class StateStorageController:
             RuntimeError if we don't have a state group for one or more of the events
                 (ie they are outliers or unknown)
         """
-        if (
-            await_full_state
-            and state_filter
-            and not state_filter.must_await_full_state(self._is_mine_id)
+        if state_filter is None:
+            state_filter = StateFilter.all()
+
+        if await_full_state and not state_filter.must_await_full_state(
+            self._is_mine_id
         ):
             # Full state is not required if the state filter is restrictive enough.
             await_full_state = False
@@ -306,7 +310,7 @@ class StateStorageController:
 
         groups = set(event_to_groups.values())
         group_to_state = await self.stores.state._get_state_for_groups(
-            groups, state_filter or StateFilter.all()
+            groups, state_filter
         )
 
         event_to_state = {
@@ -335,9 +339,10 @@ class StateStorageController:
             RuntimeError if we don't have a state group for the event (ie it is an
                 outlier or is unknown)
         """
-        state_map = await self.get_state_for_events(
-            [event_id], state_filter or StateFilter.all()
-        )
+        if state_filter is None:
+            state_filter = StateFilter.all()
+
+        state_map = await self.get_state_for_events([event_id], state_filter)
         return state_map[event_id]
 
     @trace
@@ -365,9 +370,12 @@ class StateStorageController:
             RuntimeError if we don't have a state group for the event (ie it is an
                 outlier or is unknown)
         """
+        if state_filter is None:
+            state_filter = StateFilter.all()
+
         state_map = await self.get_state_ids_for_events(
             [event_id],
-            state_filter or StateFilter.all(),
+            state_filter,
             await_full_state=await_full_state,
         )
         return state_map[event_id]
@@ -388,9 +396,12 @@ class StateStorageController:
                 at the event and `state_filter` is not satisfied by partial state.
                 Defaults to `True`.
         """
+        if state_filter is None:
+            state_filter = StateFilter.all()
+
         state_ids = await self.get_state_ids_for_event(
             event_id,
-            state_filter=state_filter or StateFilter.all(),
+            state_filter=state_filter,
             await_full_state=await_full_state,
         )
 
@@ -426,6 +437,9 @@ class StateStorageController:
                 at the last event in the room before `stream_position` and
                 `state_filter` is not satisfied by partial state. Defaults to `True`.
         """
+        if state_filter is None:
+            state_filter = StateFilter.all()
+
         # 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.
@@ -442,7 +456,7 @@ class StateStorageController:
         if last_event_id:
             state = await self.get_state_after_event(
                 last_event_id,
-                state_filter=state_filter or StateFilter.all(),
+                state_filter=state_filter,
                 await_full_state=await_full_state,
             )
 
@@ -500,9 +514,10 @@ class StateStorageController:
         Returns:
             Dict of state group to state map.
         """
-        return await self.stores.state._get_state_for_groups(
-            groups, state_filter or StateFilter.all()
-        )
+        if state_filter is None:
+            state_filter = StateFilter.all()
+
+        return await self.stores.state._get_state_for_groups(groups, state_filter)
 
     @trace
     @tag_args
@@ -583,12 +598,13 @@ class StateStorageController:
         Returns:
             The current state of the room.
         """
-        if await_full_state and (
-            not state_filter or state_filter.must_await_full_state(self._is_mine_id)
-        ):
+        if state_filter is None:
+            state_filter = StateFilter.all()
+
+        if await_full_state and state_filter.must_await_full_state(self._is_mine_id):
             await self._partial_state_room_tracker.await_full_state(room_id)
 
-        if state_filter and not state_filter.is_full():
+        if state_filter is not None and not state_filter.is_full():
             return await self.stores.main.get_partial_filtered_current_state_ids(
                 room_id, state_filter
             )