binding-bug?

components.ace-editor.js

import Ember from 'ember';

const { get, set, computed } = Ember;

export default Ember.Component.extend({
  value: computed({
    get() {
      return this.getValue();
    },
    set(_, value) {
      this.setValue(value);
      return this.getValue();
    }
  }),

  getValue() {
    if (this._value) {
      return this._value;
    }
    return this.$('textarea').val();
  },

  setValue(value) {
    if (value == null) { return; }
    let $textarea = this.$() && this.$('textarea');

    if ($textarea) {
      if (value !== $textarea.val()) {
        $textarea.val(value);
        this.notifyPropertyChange('value');
        this._value = null;
      }
    } else {
      this._value = value;
    }
  },

  actions: {
    change() {
      get(this, 'onchange')(this.$('textarea').val());
    }
  }
});

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',

  actions: {
    set(key, value) {
      this.set(key, value);
    }
  }
});

templates.application.hbs

<button onclick={{action "set" "code" "A"}}>A</button>
<button onclick={{action "set" "code" "B"}}>B</button>
<button onclick={{action "set" "code" "C"}}>C</button>
{{ace-editor value=code onchange=(action 'set' 'code')}}

templates.components.ace-editor.hbs

<textarea onchange={{action "change"}}>{{value}}</textarea>

twiddle.json

{
  "version": "0.7.2",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "1.13.13",
    "ember-data": "https://cdnjs.cloudflare.com/ajax/libs/ember-data.js/2.4.3/ember-data.js",
    "ember-template-compiler": "1.13.13"
  }
}