Remove ability to pass array of event names to EventEmitter.prototype…

….once

This functionality is implemented by wrapping the listener argument in
another listener.  This means that the event emitter does not hold a
reference to the listener argument (other than that held indirectly
through the wrapper) and so it is not possible to remove this listener
using `off(..., listener)`.

The client library specification does not specify a version of `once`
which accepts an array of event names, and we do not advertise it as
part of the public API. So, I think the simplest thing is to remove this
functionality.

Resolves #1452.

src/common/lib/client/realtimechannel.ts

@@ -165,9 +165,11 @@ class RealtimeChannel extends Channel {
       // Ignore 'attaching' -- could be just due to to a resume & reattach, should not
       // call back setOptions until we're definitely attached with the new options (or
       // else in a terminal state)
-      this._allChannelChanges.once(
+      const self = this;
+      this._allChannelChanges.on(
         ['attached', 'update', 'detached', 'failed'],
-        function (this: { event: string }, stateChange: ConnectionStateChange) {
+        function listener(this: { event: string }, stateChange: ConnectionStateChange) {
+          self._allChannelChanges.off(listener);
           switch (this.event) {
             case 'update':
             case 'attached':

src/common/lib/util/eventemitter.ts

@@ -237,14 +237,14 @@ class EventEmitter {
    * @param event the name of the event to listen to
    * @param listener the listener to be called
    */
-  once(event?: string | string[] | null, listener?: Function): void;
+  once(event?: string | null, listener?: Function): void;
 
   once(...args: unknown[]): void | Promise<void> {
     const argCount = args.length;
     if ((argCount === 0 || (argCount === 1 && typeof args[0] !== 'function')) && Platform.Config.Promise) {
       const event = args[0];
       return new Platform.Config.Promise((resolve) => {
-        this.once(event as string | string[] | null, resolve);
+        this.once(event as string | null, resolve);
       });
     }
 
@@ -256,21 +256,6 @@ class EventEmitter {
         throw new Error('EventEmitter.once(): Invalid arguments:' + Platform.Config.inspect(args));
       }
       this.anyOnce.push(secondArg);
-    } else if (Utils.isArray(firstArg)) {
-      const self = this;
-      const listenerWrapper = function (this: any) {
-        const innerArgs = Array.prototype.slice.call(arguments);
-        Utils.arrForEach(firstArg, function (eventName) {
-          self.off(eventName, listenerWrapper);
-        });
-        if (typeof secondArg !== 'function') {
-          throw new Error('EventEmitter.once(): Invalid arguments:' + Platform.Config.inspect(args));
-        }
-        secondArg.apply(this, innerArgs);
-      };
-      Utils.arrForEach(firstArg, function (eventName) {
-        self.on(eventName, listenerWrapper);
-      });
     } else {
       if (typeof firstArg !== 'string') {
         throw new Error('EventEmitter.once(): Invalid arguments:' + Platform.Config.inspect(args));

test/realtime/event_emitter.test.js

@@ -342,31 +342,6 @@ define(['shared_helper', 'chai'], function (helper, chai) {
       closeAndFinish(done, realtime);
     });
 
-    it('arrayOfEventsWithOnce', function (done) {
-      var realtime = helper.AblyRealtime({ autoConnect: false }),
-        callbackCalled = 0,
-        eventEmitter = realtime.connection;
-
-      var callback = function (arg) {
-        callbackCalled += 1;
-        expect(arg).to.equal('expected');
-      };
-
-      try {
-        callbackCalled = 0;
-        eventEmitter.once(['a', 'b', 'c'], callback);
-        eventEmitter.emit('a', 'expected');
-        eventEmitter.emit('b', 'wrong');
-        eventEmitter.emit('c', 'wrong');
-        expect(callbackCalled).to.equal(1, 'listener called back only once, for the first event emitted');
-      } catch (err) {
-        closeAndFinish(done, realtime, err);
-        return;
-      }
-
-      closeAndFinish(done, realtime);
-    });
-
     /* check that listeners added in a listener cb are not called during that
      * emit instance */
     it('listenerAddedInListenerCb', function (done) {
@@ -481,19 +456,6 @@ define(['shared_helper', 'chai'], function (helper, chai) {
             closeAndFinish(done, realtime, err);
           });
         });
-
-        it('arrayOfEventsWithOnce', function (done) {
-          var realtime = helper.AblyRealtime({ autoConnect: false }),
-            eventEmitter = realtime.connection;
-
-          const p = eventEmitter.once(['a', 'b', 'c']);
-          eventEmitter.emit('b');
-          p.then(function () {
-            closeAndFinish(done, realtime);
-          }).catch(function (err) {
-            closeAndFinish(done, realtime, err);
-          });
-        });
       });
     }
   });