Inconsistent REST behavior

Has anyone seen Rails save nested associations despite their being
invalid?

If I hit the site from a different Rails app (using ActiveResource)
and try to update the record so that the username is too short it
fails (as I expect) and adds an errors attribute to the object that I
can inspect. The original account (and associated user and email
objects) is unaffected, as I’d expect.

Hitting the same exact URL with a raw HTTP/REST client and sending in
XML:

<?xml version="1.0" encoding="UTF-8"?> 1 2010-01-05 soto [email protected] true false

It gives me the expected 422 Unprocessible Entity error, which I
expect. However it also saves user down as a null! That I do not
expect.

My question is why does it correctly handle errors with ActiveResource
(eg. doesn’t save anything down since their are validation problems)
but with a raw PUT request it saves with a null user object
(effectively killing the user).

models

class User < ActiveRecord::Base
belongs_to :account

validates_length_of :username, :minimum => 6

end

class Account < ActiveRecord::Base

has_one :user
has_one :email

has_many :account_entitlements
has_many :entitlements, :through => :account_entitlements

accepts_nested_attributes_for :user, :email

def user=(params)
update_attributes(:user_attributes => params)
end

def email=(params)
update_attributes(:email_attributes => params)
end

end

controller

def update
@account = Account.find(params[:id])

respond_to do |format|
  if @account.update_attributes(params[:account])
    flash[:notice] = 'Account was successfully updated.'
    format.html { redirect_to(@account) }
    format.xml  { head :ok }
  else
    format.html { render :action => "edit" }
    format.xml  { render :xml => @account.errors, :status

=> :unprocessable_entity }
end
end
end