Using a computed property for a Component's isVisible property breaks with Glimmer.

[Kerrick]

Example JSBins: Ember 1.13.0-beta.1 (broken) | Ember 1.12.0 (working)

Code:

App.ApplicationController = Ember.Controller.extend({
  isExpanded: false,
  actions: {
    toggle: function() {
      this.toggleProperty('isExpanded');
    }
  }
});

App.FooMenuComponent = Ember.Component.extend({
  isVisible: Ember.computed.bool('attrs.is-expanded')
});

<foo-menu is-expanded={{isExpanded}} />
<button {{action "toggle"}}>Toggle FooMenuComponent</button>

I would expect the foo-menu to be hidden when the page loads, as it is in Ember 1.12.0, but it is visible when the page loads. However, toggling the button back and forth does get it back in sync and causes it to start behaving as expected from then on.

[Kerrick]

A temporary workaround for those who want this functionality but don't want to leave the beta: switch to an observer. Workaround JSBin

App.FooMenuComponent = Ember.Component.extend({
  // isVisible: Ember.computed.bool('attrs.is-expanded')
  isExpandedChanged: Ember.observer('attrs.is-expanded', function() {
    this.set('isVisible', this.get('attrs.is-expanded'));
  })
});