Ember data fu

adapters.bar.js

import { run, later } from '@ember/runloop';
import { reject } from 'rsvp';
import DS from 'ember-data';
const { Adapter } = DS;

const OUTCOMES = {
  RESOLVE: 1, // Confirm that ember-data is working as expected
  REJECT: 2,  // ember-data should fail but does not (isRejected === false)
  ERROR: 3    // ember-data does fail as expected (isRejected === true)
};

// Change this variable to see the different situations.
const FAIL_MODE = OUTCOMES.REJECT;

async function notImplemented(methodName) {
  return function() {
    console.log(methodName, ...arguments);
    throw new Error(`${methodName} not implemented`);
  };
}

export default Adapter.extend({
  findRecord(_, __, id) {
    return new Promise(resolve => later(() => run(resolve), 2000)).then(() => {
      switch (FAIL_MODE) {
        case OUTCOMES.RESOLVE:
          return { data: { type: 'bar', id } };
        case OUTCOMES.REJECT:
          return reject();
        case OUTCOMES.ERROR:
          throw new Error('Bork');
      }
    });
  },
  createRecord: notImplemented('createRecord'),
  updateRecord: notImplemented('updaterecord'),
  deleteRecord: notImplemented('deleteRecord'),
  findAll: notImplemented('findAll'),
  query: notImplemented('query'),  
  queryRecord: notImplemented('queryrecord')
});

adapters.foo.js

import DS from 'ember-data';
const { Adapter } = DS;

async function notImplemented(methodName) {
  return function() {
    console.log(methodName, ...arguments);
    throw new Error(`${methodName} not implemented`);
  };
}

export default Adapter.extend({
  async findAll() {
    return {
      data: [
        {
          type: 'foo',
          id: '1',
          relationships: {
            bar: { data: { type: 'bar', id: '1' } }
          }
        },
        {
          type: 'foo',
          id: '2',
          relationships: {
            bar: { data: { type: 'bar', id: '2' } }
          }
        },
        {
          type: 'foo',
          id: '3',
          relationships: {
            bar: { data: { type: 'bar', id: '3' } }
          }
        }
      ]
    };
  },
  createRecord: notImplemented('createRecord'),
  updateRecord: notImplemented('updaterecord'),
  deleteRecord: notImplemented('deleteRecord'),
  findRecord: notImplemented('findRecord'),
  query: notImplemented('query'),  
  queryRecord: notImplemented('queryrecord')
});

models.bar.js

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

export default Model.extend({
});

models.foo.js

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

export default Model.extend({
  bar: belongsTo('bar')
});

routes.application.js

import Ember from 'ember';

export default Ember.Route.extend({
  model() {
    return this.store.findAll('foo');
  }
});

serializers.application.js

import JSONAPISerializer from 'ember-data/serializers/json-api';

export default JSONAPISerializer.extend({
//  normalizeResponse(_, __, payload) {
//    return payload;
//  }
});

templates.application.hbs

{{#each model as |foo|}}
  <li>
    Foo: {{foo.id}} / Bar:
    {{#if foo.bar.isPending}}
      Loading&hellip;
    {{else if foo.bar.isRejected}}
      &lt;{{foo.bar.reason}}&gt;
    {{else}}
      {{foo.bar.id}}
    {{/if}}
  </li>
{{/each}}

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"
  }
}