Don't notify belongsTo changes if nothing changed

[wecc]

Fixes #4579

[BryanCrotaz]

Looks good

[stefanpenner]

Can we define these models at the module level, that way our tests don't have to constantly recreate these classes. This scenario likely doesn't affect the overall test run speed so much, but in aggregate they really do add up

[igorT]

As a next improvement, maybe we should also check for equality with current state.

[Exelord]

@wecc
Hey.
What about this tests? I added tests also for HasMany and they all just fail. But the didn't on v2.10.0

import setupStore from 'dummy/tests/helpers/store';
import Ember from 'ember';
import DS from 'ember-data';
import { module, test } from 'qunit';

const { run } = Ember;
const { attr, belongsTo, Model, hasMany } = DS;

const Author = Model.extend({
  name: attr('string'),
  posts: hasMany()
});

const Post = Model.extend({
  author: belongsTo()
});

let env;

module('integration/records/relationship-changes - Relationship changes', {
  beforeEach() {
    env = setupStore({
      author: Author,
      post: Post
    });
  },

  afterEach() {
    run(function() {
      env.container.destroy();
    });
  }
});

test('Calling push with updated belongsTo relationship trigger observer', function(assert) {
  assert.expect(1);

  let observerCount = 0;

  run(function() {
    let post = env.store.push({
      data: {
        type: 'post',
        id: '1',
        relationships: {
          author: {
            data: { type: 'author', id: '2' }
          }
        }
      }
    });

    post.addObserver('author', function() {
      observerCount++;
    });

    env.store.push({
      data: {
        type: 'post',
        id: '1',
        relationships: {
          author: {
            data: { type: 'author', id: '3' }
          }
        }
      }
    });
  });

  assert.equal(observerCount, 1, 'author observer should be triggered once');
});

test('Calling push with same belongsTo relationship does not trigger observer', function(assert) {
  assert.expect(1);

  let observerCount = 0;

  run(function() {
    let post = env.store.push({
      data: {
        type: 'post',
        id: '1',
        relationships: {
          author: {
            data: { type: 'author', id: '2' }
          }
        }
      }
    });

    post.addObserver('author', function() {
      observerCount++;
    });

    env.store.push({
      data: {
        type: 'post',
        id: '1',
        relationships: {
          author: {
            data: { type: 'author', id: '2' }
          }
        }
      }
    });
  });

  assert.equal(observerCount, 0, 'author observer should not be triggered');
});

test('Calling push with non empty hasMany relationship does trigger observer', function(assert) {
  assert.expect(1);

  let observerCount = 0;

  run(function() {
    let author = env.store.push({
      data: {
        id: '2',
        type: 'author',
        relationships: {
          posts: {
            data: [{ type: 'post', id: '2' }]
          }
        }
      }
    });

    author.addObserver('posts', function() {
      observerCount++;
    });

    env.store.push({
      data: {
        type: 'post',
        id: '1',
        relationships: {
          author: {
            data: { type: 'author', id: '2' }
          }
        }
      }
    });
  });

  assert.equal(observerCount, 1, 'posts observer should be triggered');
});

test('Calling push with same hasMany relationship does not trigger observer', function(assert) {
  assert.expect(1);

  let observerCount = 0;

  run(function() {
    let author = env.store.push({
      data: {
        id: '2',
        type: 'author',
        relationships: {
          posts: {
            data: [{ type: 'post', id: '2' }]
          }
        }
      }
    });

    author.addObserver('posts', function() {
      observerCount++;
    });

    env.store.push({
      data: {
        type: 'post',
        id: '2',
        relationships: {
          author: {
            data: { type: 'author', id: '2' }
          }
        }
      }
    });
  });

  assert.equal(observerCount, 1, 'posts observer should not be triggered');
});

test('Calling push with empty hasMany relationship does trigger observer', function(assert) {
  assert.expect(1);

  let observerCount = 0;

  run(function() {
    let author = env.store.push({
      data: {
        id: '2',
        type: 'author'
      }
    });

    author.addObserver('posts', function() {
      observerCount++;
    });

    env.store.push({
      data: {
        type: 'post',
        id: '1',
        relationships: {
          author: {
            data: { type: 'author', id: '2' }
          }
        }
      }
    });
  });

  assert.equal(observerCount, 1, 'posts observer should be triggered');
});

after your changes, this case just stopped working :/
@stefanpenner can you also look at it? I will be thankful. It is hardly blocking our project from an upgrade to 2.11 and UP.

[Exelord]

Sorry guys, this bug is associated with: #4850