Rails 3: Why `errors` Hash is empty for nested model (all errors are in the parent model)

I'm using Devise and have models set up like this:

User
    has_one :profile
Profile
    belongs_to :user
    has_one :address
Address 
    belongs_to :pro开发者_JAVA技巧file

For testing, I caused errors on the form (it's a nested form, using all 3 models). This is the resulting errors hash (@user.errors hash):

{
:email=>["can't be blank"], 
:password_confirmation=>[], 
:password=>["can't be blank"],
:"profile.first_name"=>["can't be blank","is too short (minimum is 1 characters)"]
:"profile.address.street"=>["can't be blank"], 
}

All the errors are expected, but the hash's key format is unexpected (:"profile.address.street") - I would have thought each nested model's errors hash would contain the errors for that model ?

I checked inside the @user.profile.errors hash, and that is empty!

How do I get the nested-model specific errors into the relevant errors hash in the nested model?

UPDATE

I hacked out a solution here. Had a question on that too, so the solution isn't posted as an answer to this question :)

Ran into this not too long ago and had to cook up some code to pluck these out myself. It isn't supported by default in Rails - Ryan Daigle touches on it here a bit.

Try this:

@user.profile.valid?
@user.profile.errors