Adding objects to a hasMany destroys other hasMany associations after save()

[mattaddy]

Lets say I have the following application

var App = Ember.Application.create();

App.ApplicationAdapter = DS.FirebaseAdapter.extend({
  firebase: new Firebase('https://<my-app>.firebaseio.com')
});

App.User = DS.Model.extend({
  name: DS.attr('string'),
  posts: DS.hasMany('post', { async: true }),
  comments: DS.hasMany('comment', { async: true })
});

App.Post = DS.Model.extend({
  body: DS.attr('string')
});

App.Comment = DS.Model.extend({
  body: DS.attr('string')
});

And add a few posts to a given user (interacting with the Chrome console)

var store = App.__container__.lookup('store:main');

store.find('user', 1).then(function(u) {
  window.user = u
});

post1 = store.createRecord('post', { body: 'Post 1' });
post2 = store.createRecord('post', { body: 'Post 2' });
post3 = store.createRecord('post', { body: 'Post 3' });

user.get('posts').then(function(posts) {
  posts.addObjects([post1, post2, post3]);
  user.save().then(function() {
    post1.save();
    post2.save();
    post3.save();
  })
});

Creates the posts and associates them correctly in Firebase.

However, adding a comment to the user after the posts are saved results in the posts object being removed in Firebase

comment = store.createRecord('comment', { body: 'Comment 1' });

user.get('comments').then(function(comments) {
  comments.addObject(comment);
  user.save().then(function() { // this line destroys the user.posts object
    comment.save();
  })
});

[mattaddy]

Before creating and associating the comment with the user, calling user.get('posts.length') returns 0.

[aputinski]

@mattaddy I'm working with @jakejuby to get a fix out for this soon.