didReceiveAttrs array changes

application.controller.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName:'Ember Twiddle',
  items: Ember.A([
    'Item 1',
    'Item 2',
    'Item 3',
    'Item 4'
  ]),
  actions: {
    addItem() {
      let text = this.get('itemText');
      this.get('items').pushObject(text);
    }
  }
});

application.template.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
{{my-component items=items}}
<br>
{{input value=itemText}}
<button onclick={{action "addItem"}}>Add Item</button>
<br>

my-component.component.js

import Ember from 'ember';

export default Ember.Component.extend({
  didUpdateAttrs() {
    //never triggers when an item is added
    console.log(...arguments);
    alert('didUpdateAttrs');
  }
});

my-component.template.hbs

<ul>
{{#each items as |i|}}
  <li>{{i}}</li>
{{/each}}
</ul>

twiddle.json

{
  "version": "0.5.0",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "https://cdnjs.cloudflare.com/ajax/libs/ember.js/2.2.0/ember.debug.js",
    "ember-data": "https://cdnjs.cloudflare.com/ajax/libs/ember-data.js/2.2.0/ember-data.js",
    "ember-template-compiler": "https://cdnjs.cloudflare.com/ajax/libs/ember.js/2.2.0/ember-template-compiler.js"
  }
}