Split out ready states of stores to its own store

src/stores/AsyncStoreWithClient.ts

@@ -18,22 +18,33 @@ import { MatrixClient } from "matrix-js-sdk/src/client";
 import { AsyncStore } from "./AsyncStore";
 import { ActionPayload } from "../dispatcher/payloads";
 import { Dispatcher } from "flux";
-import { MatrixClientPeg } from "../MatrixClientPeg";
+import { ReadyWatchingStore } from "./ReadyWatchingStore";
 
 export abstract class AsyncStoreWithClient<T extends Object> extends AsyncStore<T> {
-    protected matrixClient: MatrixClient;
-
-    protected abstract async onAction(payload: ActionPayload);
+    private readyStore: ReadyWatchingStore;
 
     protected constructor(dispatcher: Dispatcher<ActionPayload>, initialState: T = <T>{}) {
         super(dispatcher, initialState);
 
-        if (MatrixClientPeg.get()) {
-            this.matrixClient = MatrixClientPeg.get();
+        // Create an anonymous class to avoid code duplication
+        const asyncStore = this;
+        this.readyStore = new (class extends ReadyWatchingStore {
+            public get mxClient(): MatrixClient {
+                return this.matrixClient;
+            }
 
-            // noinspection JSIgnoredPromiseFromCall
-            this.onReady();
-        }
+            protected async onReady(): Promise<any> {
+                return asyncStore.onReady();
+            }
+
+            protected async onNotReady(): Promise<any> {
+                return asyncStore.onNotReady();
+            }
+        })(dispatcher);
+    }
+
+    protected get matrixClient(): MatrixClient {
+        return this.readyStore.mxClient;
     }
 
     protected async onReady() {
@@ -44,30 +55,9 @@ export abstract class AsyncStoreWithClient<T extends Object> extends AsyncStore<
         // Default implementation is to do nothing.
     }
 
+    protected abstract async onAction(payload: ActionPayload);
+
     protected async onDispatch(payload: ActionPayload) {
         await this.onAction(payload);
-
-        if (payload.action === 'MatrixActions.sync') {
-            // Only set the client on the transition into the PREPARED state.
-            // Everything after this is unnecessary (we only need to know once we have a client)
-            // and we intentionally don't set the client before this point to avoid stores
-            // updating for every event emitted during the cached sync.
-            if (!(payload.prevState === 'PREPARED' && payload.state !== 'PREPARED')) {
-                return;
-            }
-
-            if (this.matrixClient !== payload.matrixClient) {
-                if (this.matrixClient) {
-                    await this.onNotReady();
-                }
-                this.matrixClient = payload.matrixClient;
-                await this.onReady();
-            }
-        } else if (payload.action === 'on_client_not_viable' || payload.action === 'on_logged_out') {
-            if (this.matrixClient) {
-                await this.onNotReady();
-                this.matrixClient = null;
-            }
-        }
     }
 }

src/stores/ReadyWatchingStore.ts

@@ -0,0 +1,81 @@
+/*
+ * 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 { MatrixClient } from "matrix-js-sdk/src/client";
+import { MatrixClientPeg } from "../MatrixClientPeg";
+import { ActionPayload } from "../dispatcher/payloads";
+import { Dispatcher } from "flux";
+import { IDestroyable } from "../utils/IDestroyable";
+import { EventEmitter } from "events";
+
+export abstract class ReadyWatchingStore extends EventEmitter implements IDestroyable {
+    protected matrixClient: MatrixClient;
+    private readonly dispatcherRef: string;
+
+    constructor(protected readonly dispatcher: Dispatcher<ActionPayload>) {
+        super();
+
+        this.dispatcherRef = this.dispatcher.register(this.onAction);
+
+        if (MatrixClientPeg.get()) {
+            this.matrixClient = MatrixClientPeg.get();
+
+            // noinspection JSIgnoredPromiseFromCall
+            this.onReady();
+        }
+    }
+
+    public get mxClient(): MatrixClient {
+        return this.matrixClient; // for external readonly access
+    }
+
+    public destroy() {
+        this.dispatcher.unregister(this.dispatcherRef);
+    }
+
+    protected async onReady() {
+        // Default implementation is to do nothing.
+    }
+
+    protected async onNotReady() {
+        // Default implementation is to do nothing.
+    }
+
+    private onAction = async (payload: ActionPayload) => {
+        if (payload.action === 'MatrixActions.sync') {
+            // Only set the client on the transition into the PREPARED state.
+            // Everything after this is unnecessary (we only need to know once we have a client)
+            // and we intentionally don't set the client before this point to avoid stores
+            // updating for every event emitted during the cached sync.
+            if (!(payload.prevState === 'PREPARED' && payload.state !== 'PREPARED')) {
+                return;
+            }
+
+            if (this.matrixClient !== payload.matrixClient) {
+                if (this.matrixClient) {
+                    await this.onNotReady();
+                }
+                this.matrixClient = payload.matrixClient;
+                await this.onReady();
+            }
+        } else if (payload.action === 'on_client_not_viable' || payload.action === 'on_logged_out') {
+            if (this.matrixClient) {
+                await this.onNotReady();
+                this.matrixClient = null;
+            }
+        }
+    };
+}