POC: Promise never resolves

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  logs: [],
  
  returnsAPromise(shouldResolve) {
    return new Ember.RSVP.Promise(resolve => {
      const promise = shouldResolve ? Ember.RSVP.resolve('yay! 🎉') : Ember.RSVP.reject('boo 😬');
      
      return promise
        .then(value => {
           this.log("Then from returned promise", value);
           resolve(value);
         })
        .catch(err => {
           // Because promise is never resolved OR rejected, it never resolves.
           this.log("Catch from returned promise", err);
        });
    });
  },
  
  log(...lines) {
    this.get('logs').pushObject(lines.join(', '));
  },
  
  actions: {
    callPromise(shouldResolve) {
      this.returnsAPromise(shouldResolve)
        .then(value => this.log("Then from caller", value))
        .catch(err => this.log("Catch from caller", err))
        .finally(() => this.log("Finally from caller"));
    }
  }
});

templates.application.hbs

<button onclick={{action (action "callPromise" true)}}>Resolve promise</button>

<button onclick={{action (action "callPromise" false)}}>Reject promise</button>

<ul style="font-family: monospace;">
{{#each logs as |logLine|}}
  <li>{{logLine}}</li>
{{/each}}
</ul>

twiddle.json

{
  "version": "0.13.0",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.16.2",
    "ember-template-compiler": "2.16.2",
    "ember-testing": "2.16.2"
  },
  "addons": {
    "ember-data": "2.16.3"
  }
}