Try putting room list handling behind a lock

Some of the logs relating to room list corruption appear to be badly timed race conditions so we'll try to linearize them here.

src/stores/room-list/algorithms/Algorithm.ts

@@ -34,6 +34,7 @@ import { OrderingAlgorithm } from "./list-ordering/OrderingAlgorithm";
 import { getListAlgorithmInstance } from "./list-ordering";
 import SettingsStore from "../../../settings/SettingsStore";
 import { VisibilityProvider } from "../filters/VisibilityProvider";
+import {MultiLock} from "../../../utils/MultiLock";
 
 /**
  * Fired when the Algorithm has determined a list has been updated.
@@ -77,6 +78,7 @@ export class Algorithm extends EventEmitter {
     } = {};
     private allowedByFilter: Map<IFilterCondition, Room[]> = new Map<IFilterCondition, Room[]>();
     private allowedRoomsByFilters: Set<Room> = new Set<Room>();
+    private handlerLock = new MultiLock();
 
     /**
      * Set to true to suspend emissions of algorithm updates.
@@ -677,6 +679,12 @@ export class Algorithm extends EventEmitter {
      * processing.
      */
     public async handleRoomUpdate(room: Room, cause: RoomUpdateCause): Promise<boolean> {
+        if (SettingsStore.getValue("advancedRoomListLogging")) {
+            // TODO: Remove debug: https://github.com/vector-im/element-web/issues/14602
+            console.log(`Acquiring lock for ${room.roomId} with cause ${cause}`);
+        }
+        const release = await this.handlerLock.acquire(room.roomId);
+        try {
             if (SettingsStore.getValue("advancedRoomListLogging")) {
                 // TODO: Remove debug: https://github.com/vector-im/element-web/issues/14602
                 console.log(`Handle room update for ${room.roomId} called with cause ${cause}`);
@@ -865,5 +873,8 @@ export class Algorithm extends EventEmitter {
                 console.log(`[RoomListDebug] Finished handling ${room.roomId} with cause ${cause} (changed=${changed})`);
             }
             return changed;
+        } finally {
+            release();
+        }
     }
 }

src/utils/MultiLock.ts

@@ -0,0 +1,30 @@
+/*
+Copyright 2021 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+import {EnhancedMap} from "./maps";
+import AwaitLock from "await-lock";
+
+export type DoneFn = () => void;
+
+export class MultiLock {
+    private locks = new EnhancedMap<string, AwaitLock>();
+
+    public async acquire(key: string): Promise<DoneFn> {
+        const lock = this.locks.getOrCreate(key, new AwaitLock());
+        await lock.acquireAsync();
+        return () => lock.release();
+    }
+}