SystemStackError with has_one

Upgrading a project of mine from Rails 2.0.3 to Rails 2.1 I discovered a number of specs started throwing errors like:

Exception raised:

Class:

Message: <"stack level too deep">

---Backtrace---

./test/cases/../../lib/../../activesupport/lib/active_support/callbacks.rb:272:in `run_callbacks'

./test/cases/../../lib/active_record/validations.rb:929:in `valid_without_callbacks?'

./test/cases/../../lib/active_record/callbacks.rb:267:in `valid?'

./test/cases/../../lib/active_record/associations/association_proxy.rb:177:in `send'

./test/cases/../../lib/active_record/associations/association_proxy.rb:177:in `method_missing'

./test/cases/../../lib/active_record/associations.rb:1165:in `validate_associated_records_for_inverse'

./test/cases/../../lib/../../activesupport/lib/active_support/callbacks.rb:173:in `send'

./test/cases/../../lib/../../activesupport/lib/active_support/callbacks.rb:173:in `evaluate_method'

./test/cases/../../lib/../../activesupport/lib/active_support/callbacks.rb:161:in `call'

./test/cases/../../lib/../../activesupport/lib/active_support/callbacks.rb:90:in `run'

./test/cases/../../lib/../../activesupport/lib/active_support/callbacks.rb:90:in `each'

./test/cases/../../lib/../../activesupport/lib/active_support/callbacks.rb:90:in `send'

./test/cases/../../lib/../../activesupport/lib/active_support/callbacks.rb:90:in `run'

./test/cases/../../lib/../../activesupport/lib/active_support/callbacks.rb:272:in `run_callbacks'

./test/cases/../../lib/active_record/validations.rb:929:in `valid_without_callbacks?'

./test/cases/../../lib/active_record/callbacks.rb:267:in `valid?'

./test/cases/../../lib/active_record/associations/association_proxy.rb:177:in `send'

this relates to an after_create callback on one of the models which has a self-referential association:

class Relationship

has_one :inverse, :class_name => 'Relationship', :foreign_key => 'inverse_id', :dependent => :nullify

def after_create

if !self.inverse

self.inverse = Relationship.find_for( contact_id, user_id )

if self.inverse

self.save!

self.inverse.inverse = self

self.inverse.save!

end

end

end

end

I have reduced the problem to a minimal test case which I have added to the appropriate test case in the ActiveRecord test suite. I enclose a patch that adds the model, fixture, and test.

To recap this behaviour functioned properly in Rails 2.0.3 but is broken in 2.1rc and 2.1final.

end