Cleanup <EventEmitter> (#3338)

src/common/__tests__/event-emitter.test.ts

@@ -0,0 +1,102 @@
+/**
+ * Copyright (c) 2021 OpenLens Authors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to
+ * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+ * the Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+ * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+import { EventEmitter } from "../event-emitter";
+
+describe("EventEmitter", () => {
+  it("should stop early if a listener returns false", () => {
+    let called = false;
+    const e = new EventEmitter<[]>();
+
+    e.addListener(() => false, {});
+    e.addListener(() => { called = true; }, {});
+    e.emit();
+
+    expect(called).toBe(false);
+  });
+
+  it("shouldn't stop early if a listener returns 0", () => {
+    let called = false;
+    const e = new EventEmitter<[]>();
+
+    e.addListener(() => 0 as any, {});
+    e.addListener(() => { called = true; }, {});
+    e.emit();
+
+    expect(called).toBe(true);
+  });
+
+  it("prepended listeners should be called before others", () => {
+    const callOrder: number[] = [];
+    const e = new EventEmitter<[]>();
+
+    e.addListener(() => { callOrder.push(1); }, {});
+    e.addListener(() => { callOrder.push(2); }, {});
+    e.addListener(() => { callOrder.push(3); }, { prepend: true });
+    e.emit();
+
+    expect(callOrder).toStrictEqual([3, 1, 2]);
+  });
+
+  it("once listeners should be called only once", () => {
+    const callOrder: number[] = [];
+    const e = new EventEmitter<[]>();
+
+    e.addListener(() => { callOrder.push(1); }, {});
+    e.addListener(() => { callOrder.push(2); }, {});
+    e.addListener(() => { callOrder.push(3); }, { once: true });
+    e.emit();
+    e.emit();
+
+    expect(callOrder).toStrictEqual([1, 2, 3, 1, 2]);
+  });
+
+  it("removeListener should stop the listener from being called", () => {
+    const callOrder: number[] = [];
+    const e = new EventEmitter<[]>();
+    const r = () => { callOrder.push(3); };
+
+    e.addListener(() => { callOrder.push(1); }, {});
+    e.addListener(() => { callOrder.push(2); }, {});
+    e.addListener(r);
+
+    e.emit();
+    e.removeListener(r);
+    e.emit();
+
+    expect(callOrder).toStrictEqual([1, 2, 3, 1, 2]);
+  });
+
+  it("removeAllListeners should stop the all listeners from being called", () => {
+    const callOrder: number[] = [];
+    const e = new EventEmitter<[]>();
+
+    e.addListener(() => { callOrder.push(1); });
+    e.addListener(() => { callOrder.push(2); });
+    e.addListener(() => { callOrder.push(3); });
+
+    e.emit();
+    e.removeAllListeners();
+    e.emit();
+
+    expect(callOrder).toStrictEqual([1, 2, 3]);
+  });
+});

src/common/event-emitter.ts

@@ -29,35 +29,31 @@ interface Options {
 type Callback<D extends [...any[]]> = (...data: D) => void | boolean;
 
 export class EventEmitter<D extends [...any[]]> {
-  protected listeners = new Map<Callback<D>, Options>();
+  protected listeners: [Callback<D>, Options][] = [];
 
   addListener(callback: Callback<D>, options: Options = {}) {
-    if (options.prepend) {
-      const listeners = [...this.listeners];
+    const fn = options.prepend ? "unshift" : "push";
 
-      listeners.unshift([callback, options]);
-      this.listeners = new Map(listeners);
-    }
-    else {
-      this.listeners.set(callback, options);
-    }
+    this.listeners[fn]([callback, options]);
   }
 
   removeListener(callback: Callback<D>) {
-    this.listeners.delete(callback);
+    this.listeners = this.listeners.filter(([cb]) => cb !== callback);
   }
 
   removeAllListeners() {
-    this.listeners.clear();
+    this.listeners.length = 0;
   }
 
   emit(...data: D) {
-    [...this.listeners].every(([callback, options]) => {
-      if (options.once) {
+    for (const [callback, { once }] of this.listeners) {
+      if (once) {
         this.removeListener(callback);
       }
 
-      return callback(...data) !== false;
-    });
+      if (callback(...data) === false) {
+        break;
+      }
+    }
   }
 }