fix(gateway): resend thread member lists on resume and leave (#3372)

fluxer_gateway/src/guild/guild_state_threads.erl

@@ -293,12 +293,16 @@ after_store_event(channel_delete, Data, Tab, State) ->
     end,
     State;
 after_store_event(guild_member_remove, Data, Tab, State) ->
-    _ =
-        case guild_state_member:extract_user_id(Data) of
-            UserId when is_integer(UserId) -> guild_thread_store:remove_user(Tab, UserId);
-            _ -> []
-        end,
-    State;
+    case guild_state_member:extract_user_id(Data) of
+        UserId when is_integer(UserId) ->
+            lists:foldl(
+                fun guild_thread_subscriptions:member_lists_changed/2,
+                State,
+                guild_thread_store:remove_user(Tab, UserId)
+            );
+        _ ->
+            State
+    end;
 after_store_event(guild_member_update, Data, _Tab, State) ->
     case guild_state_member:extract_user_id(Data) of
         UserId when is_integer(UserId) ->

fluxer_gateway/src/guild/guild_thread_subscriptions.erl

@@ -75,7 +75,6 @@ apply_threads_flag(_Other, Session) ->
 
 -spec apply_member_lists(term(), map(), guild_state()) -> {map(), [integer()]}.
 apply_member_lists(Ids, Session, State) when is_list(Ids) ->
-    Previous = maps:get(thread_member_lists, Session, []),
     Viewable = lists:sublist(
         [Id || Id <- lists:usort(Ids), viewable_thread(Session, Id, State)], ?MAX_MEMBER_LISTS
     ),
@@ -84,7 +83,7 @@ apply_member_lists(Ids, Session, State) when is_list(Ids) ->
             [] -> maps:remove(thread_member_lists, Session);
             _ -> Session#{thread_member_lists => Viewable}
         end,
-    {Updated, Viewable -- Previous};
+    {Updated, Viewable};
 apply_member_lists(_Other, Session, _State) ->
     {Session, []}.