Convert more cached return values to immutable types (#16356)

3 files changed, 10 insertions, 8 deletions

diff --git a/synapse/storage/databases/main/filtering.py b/synapse/storage/databases/main/filtering.py
index 047de6283a..7d94685caf 100644
--- a/synapse/storage/databases/main/filtering.py
+++ b/synapse/storage/databases/main/filtering.py
@@ -25,7 +25,7 @@ from synapse.storage.database import (
     LoggingTransaction,
 )
 from synapse.storage.engines import PostgresEngine
-from synapse.types import JsonDict, UserID
+from synapse.types import JsonDict, JsonMapping, UserID
 from synapse.util.caches.descriptors import cached
 
 if TYPE_CHECKING:
@@ -145,7 +145,7 @@ class FilteringWorkerStore(SQLBaseStore):
     @cached(num_args=2)
     async def get_user_filter(
         self, user_id: UserID, filter_id: Union[int, str]
-    ) -> JsonDict:
+    ) -> JsonMapping:
         # filter_id is BIGINT UNSIGNED, so if it isn't a number, fail
         # with a coherent error message rather than 500 M_UNKNOWN.
         try:
diff --git a/synapse/storage/databases/main/relations.py b/synapse/storage/databases/main/relations.py
index 6ba9c9651f..b67f780c10 100644
--- a/synapse/storage/databases/main/relations.py
+++ b/synapse/storage/databases/main/relations.py
@@ -465,7 +465,7 @@ class RelationsWorkerStore(SQLBaseStore):
     @cachedList(cached_method_name="get_references_for_event", list_name="event_ids")
     async def get_references_for_events(
         self, event_ids: Collection[str]
-    ) -> Mapping[str, Optional[List[_RelatedEvent]]]:
+    ) -> Mapping[str, Optional[Sequence[_RelatedEvent]]]:
         """Get a list of references to the given events.
 
         Args:
@@ -931,7 +931,7 @@ class RelationsWorkerStore(SQLBaseStore):
         room_id: str,
         limit: int = 5,
         from_token: Optional[ThreadsNextBatch] = None,
-    ) -> Tuple[List[str], Optional[ThreadsNextBatch]]:
+    ) -> Tuple[Sequence[str], Optional[ThreadsNextBatch]]:
         """Get a list of thread IDs, ordered by topological ordering of their
         latest reply.
 
diff --git a/synapse/storage/databases/main/roommember.py b/synapse/storage/databases/main/roommember.py
index 7b503dd697..3755773faa 100644
--- a/synapse/storage/databases/main/roommember.py
+++ b/synapse/storage/databases/main/roommember.py
@@ -984,7 +984,7 @@ class RoomMemberWorkerStore(EventsWorkerStore, CacheInvalidationWorkerStore):
         )
 
     @cached(iterable=True, max_entries=10000)
-    async def get_current_hosts_in_room_ordered(self, room_id: str) -> List[str]:
+    async def get_current_hosts_in_room_ordered(self, room_id: str) -> Tuple[str, ...]:
         """
         Get current hosts in room based on current state.
 
@@ -1013,12 +1013,14 @@ class RoomMemberWorkerStore(EventsWorkerStore, CacheInvalidationWorkerStore):
             # `get_users_in_room` rather than funky SQL.
 
             domains = await self.get_current_hosts_in_room(room_id)
-            return list(domains)
+            return tuple(domains)
 
         # For PostgreSQL we can use a regex to pull out the domains from the
         # joined users in `current_state_events` via regex.
 
-        def get_current_hosts_in_room_ordered_txn(txn: LoggingTransaction) -> List[str]:
+        def get_current_hosts_in_room_ordered_txn(
+            txn: LoggingTransaction,
+        ) -> Tuple[str, ...]:
             # Returns a list of servers currently joined in the room sorted by
             # longest in the room first (aka. with the lowest depth). The
             # heuristic of sorting by servers who have been in the room the
@@ -1043,7 +1045,7 @@ class RoomMemberWorkerStore(EventsWorkerStore, CacheInvalidationWorkerStore):
             """
             txn.execute(sql, (room_id,))
             # `server_domain` will be `NULL` for malformed MXIDs with no colons.
-            return [d for d, in txn if d is not None]
+            return tuple(d for d, in txn if d is not None)
 
         return await self.db_pool.runInteraction(
             "get_current_hosts_in_room_ordered", get_current_hosts_in_room_ordered_txn