Bug 1497457 - Allow to remove one time listeners on event-source;r=ochameau

Differential Revision: https://phabricator.services.mozilla.com/D11992

--HG--
extra : moz-landing-system : lando

devtools/shared/client/event-source.js

@@ -27,8 +27,12 @@ function eventSource(proto) {
    *        Called when the event is fired. If the same listener
    *        is added more than once, it will be called once per
    *        addListener call.
+   * @param key function (optional)
+   *        Key to use for removeListener, defaults to the listener. Used by helper method
+   *        addOneTimeListener, which creates a custom listener. Use the original listener
+   *        as key to allow to remove oneTimeListeners.
    */
-  proto.addListener = function(name, listener) {
+  proto.addListener = function(name, listener, key = listener) {
     if (typeof listener != "function") {
       throw TypeError("Listeners must be functions.");
     }
@@ -37,7 +41,7 @@ function eventSource(proto) {
       this._listeners = {};
     }
 
-    this._getListeners(name).push(listener);
+    this._getListeners(name).push({ key, callback: listener });
   };
 
   /**
@@ -53,14 +57,14 @@ function eventSource(proto) {
    */
   proto.addOneTimeListener = function(name, listener) {
     return new Promise(resolve => {
-      const l = (eventName, ...rest) => {
-        this.removeListener(name, l);
+      const oneTimeListener = (eventName, ...rest) => {
+        this.removeListener(name, listener);
         if (listener) {
           listener(eventName, ...rest);
         }
         resolve(rest[0]);
       };
-      this.addListener(name, l);
+      this.addListener(name, oneTimeListener, listener);
     });
   };
 
@@ -83,7 +87,7 @@ function eventSource(proto) {
       this._listeners[name] = [];
     } else {
       this._listeners[name] =
-        this._listeners[name].filter(l => l != listener);
+        this._listeners[name].filter(l => l.key != listener);
     }
   };
 
@@ -121,7 +125,7 @@ function eventSource(proto) {
 
     for (const listener of listeners) {
       try {
-        listener.apply(null, arguments);
+        listener.callback.apply(null, arguments);
       } catch (e) {
         // Prevent a bad listener from interfering with the others.
         DevToolsUtils.reportException("notify event '" + name + "'", e);

devtools/shared/tests/unit/test_eventsource.js

@@ -0,0 +1,67 @@
+/* -*- js-indent-level: 2; indent-tabs-mode: nil -*- */
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const eventSource = require("devtools/shared/client/event-source");
+
+// Test basic event-source APIs:
+// - addListener
+// - removeListener
+// - addOneTimeListener
+
+add_task(function() {
+  // Create a basic test object that can emit events using event-source.js
+  class TestClass {}
+  eventSource(TestClass.prototype);
+  const testObject = new TestClass();
+
+  testBasicAddRemoveListener(testObject);
+
+  info("Check that one time listeners are only triggered once");
+  testOneTimeListener(testObject);
+
+  info("Check that one time listeners can be removed");
+  testRemoveOneTimeListener(testObject);
+});
+
+function testBasicAddRemoveListener(testObject) {
+  let eventsReceived = 0;
+  const onTestEvent = () => eventsReceived++;
+
+  testObject.addListener("event-testBasicAddRemoveListener", onTestEvent);
+  testObject.emit("event-testBasicAddRemoveListener");
+  ok(eventsReceived === 1, "Event listener was triggered");
+
+  testObject.emit("event-testBasicAddRemoveListener");
+  ok(eventsReceived === 2, "Event listener was triggered again");
+
+  testObject.removeListener("event-testBasicAddRemoveListener", onTestEvent);
+  testObject.emit("event-testBasicAddRemoveListener");
+  ok(eventsReceived === 2, "Event listener was not triggered anymore");
+}
+
+function testOneTimeListener(testObject) {
+  let eventsReceived = 0;
+  const onTestEvent = () => eventsReceived++;
+
+  testObject.addOneTimeListener("event-testOneTimeListener", onTestEvent);
+  testObject.emit("event-testOneTimeListener");
+  ok(eventsReceived === 1, "Event listener was triggered");
+
+  testObject.emit("event-testOneTimeListener");
+  ok(eventsReceived === 1, "Event listener was not triggered again");
+
+  testObject.removeListener("event-testOneTimeListener", onTestEvent);
+}
+
+function testRemoveOneTimeListener(testObject) {
+  let eventsReceived = 0;
+  const onTestEvent = () => eventsReceived++;
+
+  testObject.addOneTimeListener("event-testRemoveOneTimeListener", onTestEvent);
+  testObject.removeListener("event-testRemoveOneTimeListener", onTestEvent);
+  testObject.emit("event-testRemoveOneTimeListener");
+  ok(eventsReceived === 0, "Event listener was already removed");
+}

devtools/shared/tests/unit/xpcshell.ini

@@ -16,6 +16,7 @@ support-files =
 run-if = nightly_build
 [test_eventemitter_basic.js]
 [test_eventemitter_static.js]
+[test_eventsource.js]
 [test_fetch-bom.js]
 [test_fetch-chrome.js]
 [test_fetch-file.js]