Asynchronously Fetched Default Param Value Ember 2.12

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle'
});

router.js

import EmberRouter from '@ember/routing/router';
import config from './config/environment';

const Router = EmberRouter.extend({
  location: 'none',
  rootURL: config.rootURL
});

Router.map(function() {
  this.route('parent', function() {
    this.route('child');
  });
  this.route('sibling');
});

export default Router;

routes.index.js

import Ember from 'ember';

export default Ember.Route.extend({
  beforeModel() {
    console.log('index');
    this.replaceWith('parent');
  }
});

routes.parent.child.js

import Ember from 'ember';

export default Ember.Route.extend({
  beforeModel() {
    console.log('parent.child');
  }
});

routes.parent.index.js

import Ember from 'ember';

export default Ember.Route.extend({
  beforeModel() {
    console.log('parent.index');
  },
  redirect() {
    console.log('redirecting parent.index to parent.child');
    return this.replaceWith('parent.child');
  }
});

routes.parent.js

import Ember from 'ember';

const FETCHED_VALUE = 'fetchedValue';

export default Ember.Route.extend({
  queryParams: {
    requiredParam: {
      refreshModel: true
    },
    optionalParam: {
      refreshModel: true
    },
  },
  requiredParam: 'defaultParentValue',
  optionalParam: 'defaultParentValue',
  beforeModel(transition) {
    console.log('parent');
    
    const targetName = this.router.router.activeTransition.targetName;
    console.log('On way to', targetName);

    const currentQueryParams = transition.queryParams;
    const { requiredParam } = currentQueryParams;
    
    if (!requiredParam) {
      console.log('didn\'t have requiredParam, aborting and doing async to fetch');
      this.router.router.activeTransition.abort();

      return new Ember.RSVP.Promise(function(resolve, reject) {
        Ember.run.later(() => resolve(FETCHED_VALUE), 30);
      })
        .then((asynchronouslyFetchedValue) => {
        	console.log('resolved fetch promise');
          const requiredParam = asynchronouslyFetchedValue;

        	const queryParams = Object.assign({}, currentQueryParams, {
            requiredParam,
          });
        	console.log('Transitioning to', queryParams);
          this.replaceWith(targetName, { queryParams });
        });
    } else {
      console.log('had requiredParam', requiredParam);
    }
  }
});

routes.parent.sibling.js

import Ember from 'ember';

export default Ember.Route.extend({
  beforeModel() {
    console.log('parent.sibling');
  }
});

routes.uncle.js

import Ember from 'ember';

export default Ember.Route.extend({
  queryParams: {
    requiredParam: {
      refreshModel: true
    },
    optionalParam: {
      refreshModel: true
    },
  },
  requiredParam: 'defaultUncleValue',
  optionalParam: 'defaultUncleValue',
  beforeModel() {
    console.log('uncle');
  }
});

templates.application.hbs

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

twiddle.json

{
  "version": "0.15.0",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.js",
    "ember": "2.12.0",
    "ember-template-compiler": "2.12.0",
    "ember-testing": "2.12.0"
  },
  "addons": {
    "ember-data": "3.2.0"
  }
}