New Twiddle

components.my-component\.js

/* eslint-disable require-yield */
import Component from '@glimmer/component';
import { task, timeout, waitForProperty } from 'ember-concurrency';

export default class EventsExampleComponent extends Component {
  // BEGIN-SNIPPET waitForProperty
  @task
  *changeStore() {
    this.foo.perform();
    this.bar.perform();
  }

  @task *foo() {
    yield timeout(1000);
    return 'all good';
  }

  @task *bar() {
    let value = yield waitForProperty(this, 'foo.isIdle');
    alert(value);
  }
}

controllers.application\.js

import Controller from '@ember/controller';

export default class ApplicationController extends Controller {
  appName = 'Ember Twiddle';
}

templates.application\.hbs

<MyComponent/>

templates.components.my-component\.hbs

<h3>waitProperty bug demo: waitProperty doesn't seem to work when waiting for task's isIdle property to change</h3>

<p>
  Expected behavior: when foo task completes, its isIdle property should become true, and the
  waitForProperty(this, 'foo.isIdle') in the bar task should complete and bar should continue executing.
  Actual behavior: bar task gets stuck on waitForProperty(this, 'foo.isIdle') even when foo.isIdle becomes true
</p>

<button {{on "click" (perform this.changeStore)}} type="button">
  Start
</button>

<h5>
  {{!-- State: {{this.state}} --}}
</h5>

<h5>
  {{!-- foo.isIdle: {{foo.isIdle}} --}}
</h5>

twiddle\.json

{
  "version": "0.17.1",
  "EmberENV": {
    "FEATURES": {},
    "_TEMPLATE_ONLY_GLIMMER_COMPONENTS": false,
    "_APPLICATION_TEMPLATE_WRAPPER": true,
    "_JQUERY_INTEGRATION": true
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.5.1/jquery.js",
    "ember-source": "3.28.9"
  },
  "addons": {
    "@glimmer/component": "1.1.2",
    "ember-concurrency": "2.2.1"
  }
}