RecordArrayManager.prototype._syncLiveRecordArray bug

controllers.application.js

import Ember from 'ember';

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

models.group.js

import DS from 'ember-data';

export default DS.Model.extend({

    name: DS.attr('string')
});

models.post.js

import DS from 'ember-data';
import Ember from 'ember';

export default DS.Model.extend({

    name: DS.attr('string'),

    // async relation to trigger `RecordArrayManager._pending` while compute `authors`
    group: DS.belongsTo('group', {async: true}),

    users: Ember.computed(function () {

        return this.store.peekAll('user');
    }),

    authors: Ember.computed('users.@each.name', function () {

        return this.get('users').mapBy('name').join(',');
    })
});

models.user.js

import Model from "ember-data/model";
import attr from "ember-data/attr";

export default Model.extend({
  name: attr('string')
});

routes.application.js

import Ember from 'ember';

export default Ember.Route.extend({

    model: function () {

        let store = this.store;

      	// mock data
        store.push({
            data: [{
                type: 'user',
                id: '1',
                attributes: {
                    name: 'user 1'
                }
            },{
                type: 'user',
                id: '2',
                attributes: {
                    name: 'user 2'
                }
            }],
            included: [{
                type: 'post',
                id: '1',
                attributes: {
                    name: 'post 1'
                },
                relationships: {
                    group: {
                        data: {
                            type: 'group',
                            id: '1'
                        }
                    }
                }
            },{
                type: 'post',
                id: '2',
                attributes: {
                    name: 'post 2'
                },
                relationships: {
                    group: {
                        data: {
                            type: 'group',
                            id: '1'
                        }
                    }
                }
            }],
        });

        return {
            posts: store.peekAll('post')
        };
    }
});

templates.application.hbs

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

{{#each model.posts as |post|}}
    <div>{{post.group.name}}</div>
    <div>{{post.authors}}</div>{{!will trigger modified twice error in single render}}
{{/each}}

twiddle.json

{
  "version": "0.12.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "https://cdn.bootcss.com/ember.js/2.16.1/ember.debug.js",
    "ember-template-compiler": "release",
    "ember-data": "https://cdn.bootcss.com/ember-data.js/2.16.1/ember-data.prod.js"
  }
}