Ember 2.12.2 Set Mutations

controllers.application.js

import Ember from 'ember';

let num = 4;

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  
  emberVersion: Ember.VERSION,
  
  init() {
    this._super(...arguments);
    this.set('theSet', new Set([1,2,3]));
  },
    
  theSetItems: Ember.computed('theSet', function() {
    return Array.from(this.get('theSet'));
  }),

  theSetItemsBrackets: Ember.computed('theSet.[]', function() {
    return Array.from(this.get('theSet'));
  }),
  
  actions: {
    add1() {
      let theSet = this.get('theSet');
      theSet.add(num++);
    },
    add1AndSet() {
      let theSet = this.get('theSet');
      theSet.add(num++);
      this.set('theSet', theSet);
    },
    add1AndSetNew() {
      let theSet = this.get('theSet');
      theSet.add(num++);
      this.set('theSet', new Set(theSet));
    },
   
    notifySet() {
      this.notifyPropertyChange('theSet');
    },
  }
});

templates.application.hbs

<h1>Ember Set Mutations</h1>
<h2>Ember Version: {{emberVersion}}</h2>
<br>
<h3>theSet items (dependent key "theSet")</h3>
<ul>
  {{#each theSetItems as |item|}}
  	<li>{{item}}</li>
  {{else}}
	  <li><em>none</em></li>
  {{/each}}
 </ul>
 
 <br> <br> <br>
 <h3>theSet.[] items (dependent key "theSet.[]")</h3>
<ul>
  {{#each theSetItemsBrackets as |item|}}
  	<li>{{item}}</li>
  {{else}}
	  <li><em>none</em></li>
  {{/each}}
 </ul>
 <br> <br> <br>
 
<button {{action "add1"}}>Mutate Set (add 1)</button> -- no observable change until "notify"
<br>
<br>
<button {{action "add1AndSet"}}>Mutate Set (add 1) and "this.set('theSet', theSet)"</button> -- no observable change until "notify"
<br>
<br>
<button {{action "add1AndSetNew"}}>Mutate Set (add 1) and "this.set('theSet', new Set(theSet)"</button> -- the change will be visible immediately because the CPs depending on "theSet" will all invalidate
<br>
<br>
<button {{action "notifySet"}}>notifyPropertyChange("theSet")</button>
<br>
<br>

twiddle.json

{
  "version": "0.15.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.js",
    "ember": "2.12.2",
    "ember-template-compiler": "2.12.2",
    "ember-testing": "3.4.3"
  },
  "addons": {
    "ember-data": "2.12.2"
  }
}