Bugbear: Add Mutable Parameter fixes (#9682)

Part of #9366

Adds in fixes for B006 and B008, both relating to mutable parameter lint errors.

Signed-off-by: Jonathan de Jong <jonathan@automatia.nl>

1 files changed, 8 insertions, 3 deletions

diff --git a/synapse/handlers/message.py b/synapse/handlers/message.py
index 6069968f7f..125dae6d25 100644
--- a/synapse/handlers/message.py
+++ b/synapse/handlers/message.py
@@ -137,7 +137,7 @@ class MessageHandler:
         self,
         user_id: str,
         room_id: str,
-        state_filter: StateFilter = StateFilter.all(),
+        state_filter: Optional[StateFilter] = None,
         at_token: Optional[StreamToken] = None,
         is_guest: bool = False,
     ) -> List[dict]:
@@ -164,6 +164,8 @@ class MessageHandler:
             AuthError (403) if the user doesn't have permission to view
             members of this room.
         """
+        state_filter = state_filter or StateFilter.all()
+
         if at_token:
             # FIXME this claims to get the state at a stream position, but
             # get_recent_events_for_room operates by topo ordering. This therefore
@@ -874,7 +876,7 @@ class EventCreationHandler:
         event: EventBase,
         context: EventContext,
         ratelimit: bool = True,
-        extra_users: List[UserID] = [],
+        extra_users: Optional[List[UserID]] = None,
         ignore_shadow_ban: bool = False,
     ) -> EventBase:
         """Processes a new event.
@@ -902,6 +904,7 @@ class EventCreationHandler:
         Raises:
             ShadowBanError if the requester has been shadow-banned.
         """
+        extra_users = extra_users or []
 
         # we don't apply shadow-banning to membership events here. Invites are blocked
         # higher up the stack, and we allow shadow-banned users to send join and leave
@@ -1071,7 +1074,7 @@ class EventCreationHandler:
         event: EventBase,
         context: EventContext,
         ratelimit: bool = True,
-        extra_users: List[UserID] = [],
+        extra_users: Optional[List[UserID]] = None,
     ) -> EventBase:
         """Called when we have fully built the event, have already
         calculated the push actions for the event, and checked auth.
@@ -1083,6 +1086,8 @@ class EventCreationHandler:
             it was de-duplicated (e.g. because we had already persisted an
             event with the same transaction ID.)
         """
+        extra_users = extra_users or []
+
         assert self.storage.persistence is not None
         assert self._events_shard_config.should_handle(
             self._instance_name, event.room_id