New Twiddle

controllers.application\.js

import Controller from '@ember/controller';
import { tracked, cached } from '@glimmer/tracking';

function cachedWithKey(invalidationKey) {
  return function(target, key, descriptor) {
    let _v;
    let hasComputed = false;
    let cacheddesc = cached(target, key, {
      get() {
        this[target][key];
      }
    });
    
    return {
      configurable: true,
      writable: true,
      get() {
        cacheddesc.get.call(this);
        _v = descriptor.get.call(this); 
      }
    }
  };
}

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

	get expensiveThing() {
    let callCount = 0;
    this.callCount++;
  }

}

templates.application\.hbs

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

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": "3.18.1",
    "ember-template-compiler": "3.18.1",
    "ember-testing": "3.18.1"
  },
  "addons": {
    "@glimmer/component": "1.0.0"
  }
}