mypy plugin to check `@cached` return types (#14911)

Co-authored-by: David Robertson <davidr@element.io>
Co-authored-by: Patrick Cloke <patrickc@matrix.org>
Co-authored-by: Erik Johnston <erik@matrix.org>

Assert that the return type of callables wrapped in @cached
and @cachedList are cachable (aka immutable). 

1 files changed, 2 insertions, 2 deletions

diff --git a/synapse/handlers/room_list.py b/synapse/handlers/room_list.py

index bb0bdb8e6f..36e2db8975 100644
--- a/synapse/handlers/room_list.py
+++ b/synapse/handlers/room_list.py
@@ -33,7 +33,7 @@ from synapse.api.errors import (
     RequestSendFailed,
     SynapseError,
 )
-from synapse.types import JsonDict, ThirdPartyInstanceID
+from synapse.types import JsonDict, JsonMapping, ThirdPartyInstanceID
 from synapse.util.caches.descriptors import _CacheContext, cached
 from synapse.util.caches.response_cache import ResponseCache
 
@@ -256,7 +256,7 @@ class RoomListHandler:
         cache_context: _CacheContext,
         with_alias: bool = True,
         allow_private: bool = False,
-    ) -> Optional[JsonDict]:
+    ) -> Optional[JsonMapping]:
         """Returns the entry for a room
 
         Args: