What constitutes a run loop side effect?

[rwjblue]

Yep, that totally makes sense, and thank you for writing down your thought process (it really is helpful)!

As @ef4 mentioned, we are working to remove that auto-run assertion (hopefully by the time 3.3 or 3.4 rolls around we will have landed that). In the meantime, using async / await in application code is pretty annoying (largely because of the auto-run assertion).

For example:

// app/components/gist-edit.js
export default Component.extend({
  actions: {
    async update() {
      // using native `fetch` here (not ember-fetch)
      await fetch('https://api.github.com/gists', {
        method: 'post',
        body: JSON.stringify({ /* snip */ })
      })

      this.set('flash-alert', 'successfully updated!');
    }
  }
});

To walk this through:

1. Ember automatically invokes the update action itself within a run-loop
2. The fetch is kicked off
3. When the fetch is finished the previously started run-loop is long gone
4. The this.set('flash-alert' runs
5. Setting any property that is rendered in the DOM, schedules a re-render
6. auto-run assertion: cannot schedule when not within a run loop