Self-Referencing Relationships

adapters.application.js

import DS from 'ember-data';

export default DS.Adapter.extend({
});

controllers.application.js

import Ember from 'ember';

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

models.foo.js

import Model from 'ember-data/model';
import { belongsTo } from 'ember-data/relationships';

export default Model.extend({
  bar: belongsTo('foo'),
//  bar: belongsTo('foo', { inverse: null }),
});

routes.application.js

import Ember from 'ember';
import { inject as service } from '@ember/service';
import { resolve } from 'rsvp';

export default Ember.Route.extend({
  store: service(),
  
  model() {
    this.store.push({
      data: {
        type: 'foo',
        id: 'bar',
        relationships: {
          bar: {
            data: null,
          },
        },
      },
      included: [
        {
          type: 'foo',
          id: 'foobar',
          relationships: {
            bar: {
              data: { id: 'bar', type: 'foo' },
            },
          },
        }
      ],
    });
    return resolve(this.store.peekRecord('foo', 'foobar'));
  },
});

templates.application.hbs

Model relationship: "{{model.bar.id}}"<br>
Should be: bar

twiddle.json

{
  "version": "0.15.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.js",
    "ember": "3.4.3",
    "ember-template-compiler": "3.4.3",
    "ember-testing": "3.4.3"
  },
  "addons": {
    "ember-data": "3.4.2"
  }
}