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>

5 files changed, 18 insertions, 11 deletions

diff --git a/synapse/handlers/appservice.py b/synapse/handlers/appservice.py
index 996f9e5deb..9fb7ee335d 100644
--- a/synapse/handlers/appservice.py
+++ b/synapse/handlers/appservice.py
@@ -182,7 +182,7 @@ class ApplicationServicesHandler:
         self,
         stream_key: str,
         new_token: Optional[int],
-        users: Collection[Union[str, UserID]] = [],
+        users: Optional[Collection[Union[str, UserID]]] = None,
     ):
         """This is called by the notifier in the background
         when a ephemeral event handled by the homeserver.
@@ -215,7 +215,7 @@ class ApplicationServicesHandler:
         # We only start a new background process if necessary rather than
         # optimistically (to cut down on overhead).
         self._notify_interested_services_ephemeral(
-            services, stream_key, new_token, users
+            services, stream_key, new_token, users or []
         )
 
     @wrap_as_background_process("notify_interested_services_ephemeral")
diff --git a/synapse/handlers/federation.py b/synapse/handlers/federation.py
index 5ea8a7b603..67888898ff 100644
--- a/synapse/handlers/federation.py
+++ b/synapse/handlers/federation.py
@@ -1790,7 +1790,7 @@ class FederationHandler(BaseHandler):
         room_id: str,
         user_id: str,
         membership: str,
-        content: JsonDict = {},
+        content: JsonDict,
         params: Optional[Dict[str, Union[str, Iterable[str]]]] = None,
     ) -> Tuple[str, EventBase, RoomVersion]:
         (
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
diff --git a/synapse/handlers/register.py b/synapse/handlers/register.py
index 9701b76d0f..3b6660c873 100644
--- a/synapse/handlers/register.py
+++ b/synapse/handlers/register.py
@@ -169,7 +169,7 @@ class RegistrationHandler(BaseHandler):
         user_type: Optional[str] = None,
         default_display_name: Optional[str] = None,
         address: Optional[str] = None,
-        bind_emails: Iterable[str] = [],
+        bind_emails: Optional[Iterable[str]] = None,
         by_admin: bool = False,
         user_agent_ips: Optional[List[Tuple[str, str]]] = None,
         auth_provider_id: Optional[str] = None,
@@ -204,6 +204,8 @@ class RegistrationHandler(BaseHandler):
         Raises:
             SynapseError if there was a problem registering.
         """
+        bind_emails = bind_emails or []
+
         await self.check_registration_ratelimit(address)
 
         result = await self.spam_checker.check_registration_for_spam(
diff --git a/synapse/handlers/sync.py b/synapse/handlers/sync.py
index ff11266c67..f8d88ef77b 100644
--- a/synapse/handlers/sync.py
+++ b/synapse/handlers/sync.py
@@ -548,7 +548,7 @@ class SyncHandler:
         )
 
     async def get_state_after_event(
-        self, event: EventBase, state_filter: StateFilter = StateFilter.all()
+        self, event: EventBase, state_filter: Optional[StateFilter] = None
     ) -> StateMap[str]:
         """
         Get the room state after the given event
@@ -558,7 +558,7 @@ class SyncHandler:
             state_filter: The state filter used to fetch state from the database.
         """
         state_ids = await self.state_store.get_state_ids_for_event(
-            event.event_id, state_filter=state_filter
+            event.event_id, state_filter=state_filter or StateFilter.all()
         )
         if event.is_state():
             state_ids = dict(state_ids)
@@ -569,7 +569,7 @@ class SyncHandler:
         self,
         room_id: str,
         stream_position: StreamToken,
-        state_filter: StateFilter = StateFilter.all(),
+        state_filter: Optional[StateFilter] = None,
     ) -> StateMap[str]:
         """Get the room state at a particular stream position
 
@@ -589,7 +589,7 @@ class SyncHandler:
         if last_events:
             last_event = last_events[-1]
             state = await self.get_state_after_event(
-                last_event, state_filter=state_filter
+                last_event, state_filter=state_filter or StateFilter.all()
             )
 
         else: