Allow add/remove listeners in callbacks (videojs#119) (videojs#121)

Using a callback to mutate the listeners (e.g. removing yourself), previously
changed the iterated array, causing bugs.  Remove the problem by always copying
the array, so on()/off() become safe to call at any time.

lib/utils/stream.js

@@ -22,7 +22,7 @@ var Stream = function() {
       if (!listeners[type]) {
         listeners[type] = [];
       }
-      listeners[type].push(listener);
+      listeners[type] = listeners[type].concat(listener);
     };
     /**
      * Remove a listener for a specified event type.
@@ -36,6 +36,7 @@ var Stream = function() {
         return false;
       }
       index = listeners[type].indexOf(listener);
+      listeners[type] = listeners[type].slice();
       listeners[type].splice(index, 1);
       return index > -1;
     };

test/stream.test.js

@@ -0,0 +1,48 @@
+'use strict';
+
+var
+  stream,
+  Stream = require('../lib/utils/stream'),
+  QUnit = require('qunit');
+
+QUnit.module('Stream', {
+  beforeEach: function() {
+    stream = new Stream();
+    stream.init();
+  }
+});
+
+QUnit.test('trigger calls listeners', function() {
+  var args = [];
+
+  stream.on('test', function(data) {
+      args.push(data);
+  });
+
+  stream.trigger('test', 1);
+  stream.trigger('test', 2);
+
+  QUnit.deepEqual(args, [1, 2]);
+});
+
+QUnit.test('callbacks can remove themselves', function() {
+  var args1 = [], args2 = [], args3 = [];
+
+  stream.on('test', function(event) {
+      args1.push(event);
+  });
+  stream.on('test', function t(event) {
+      args2.push(event);
+      stream.off('test', t);
+  });
+  stream.on('test', function(event) {
+      args3.push(event);
+  });
+
+  stream.trigger('test', 1);
+  stream.trigger('test', 2);
+
+  QUnit.deepEqual(args1, [1, 2], 'first callback ran all times');
+  QUnit.deepEqual(args2, [1], 'second callback removed after first run');
+  QUnit.deepEqual(args3, [1, 2], 'third callback ran all times');
+});