2.1.0 has_many associations broken

There's a patch, i've made.

I attached a simple example illustrating the problem. There are two models Post and Comment, and a test case, prooving a bug.

Actually the problem occurs, because << does not call reload on associated object and does not get changed owner. So, in my perception, if << reload object, everything would be fine.

I've got an addition. The problem occurs only in test environment.

Hi there.

After installing 2.1.0 rails gem i experience problem with has_many associations.

It's impossible to change object owner, if it has one already.

For example:

user1 = User.create

>> #<User id: 1>

user2 = User.create

>> #<User id: 2>

char = Character.create( :user => user1 )

>> #<Character id:1, :user_id => 1>

user2.characters << char

char.user_id

>> 1

As far as i'm concirned, breaking code is situated in active_record/associations.rb, line 898, where belongs_to_before_save_for_#{reflection.name} is defined.

association is taken from char.instance_variable_get("@user") and in case it is defined, it executes char[:user_id] = @user.id.

Commenting this line make everyone happy, but i'm not sure, if it's a good idea:

1. self["#{reflection.primary_key_name}"] = association.id