New Twiddle

controllers.application\.js

import Controller from '@ember/controller';

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

mixins.foo\.js

import Mixin from '@ember/object/mixin';
let fooMixin =  Mixin.create({
  bar() {
    return "what";
  }
});
let handler = {
  get: function(obj, prop) {;
    console.log('stop including me please');
    return prop in obj ?
      obj[prop] : "whatever";
  }
};
let foo = new Proxy(fooMixin, handler);
export default foo;

routes.application\.js

import Route from '@ember/routing/route';
import FooMixin from "../mixins/foo";

export default Route.extend(FooMixin, {
  bar() {}
});

templates.application\.hbs

<h1>Welcome to {{this.appName}}</h1>
<br>
<br>
{{outlet}}
<br>
<br>

twiddle\.json

{
  "version": "0.17.0",
  "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/3.3.1/jquery.js",
    "ember": "3.17.0",
    "ember-template-compiler": "3.17.0",
    "ember-testing": "3.17.0"
  },
  "addons": {
    "@glimmer/component": "1.0.0"
  }
}