ActiveRecord attempting to autosave empty associated records after failed transactions

[moserrya]

The issue happens when creating an associated record in a transaction and that transaction fails. Models for this example:

class Person < ActiveRecord::Base
  validates_presence_of :name
  has_many :feelings
end

class Feeling < ActiveRecord::Base
  # :person_id, :description
end

Let's create a transaction wherein a person gets a new feeling:

person = Person.find(1)
person.transaction do
  person.feelings.create!(description: 'kaboom', size: 'large')
  person.update!(name: nil)
end
rescue ActiveRecord::AutosaveAssociation
person.name = 'Biglet'
person.save

The feeling is rightly rolled back when person.update! fails. However, if we rescue from the exception in our transaction block and call another save on the same person object later, it attempts (or succeeds) to autosave a new Feeling, but with all columns nulled out. Cannot imagine this is the correct behavior. Wanted to verify this is in fact a bug and discuss the correct behavior before I go about creating a PR.

Reproduced with AR 4.0.5, 4.1.7, 4.2.0.beta4

[rafaelfranca]

Yeah, agree it doesn't seem correct behaviour. I believe the problem here is that the rollback of the transaction doesn't put the object in the previous state before starting the transaction so the feeling object is inside your person instance, when you save, it tries to save it again.

Do you have any suggestion of what you would expect here?

[moserrya]

Let's say our person has two persisted feelings then we have the failed transaction listed above. I would expect to see two feelings when I call person.feelings, not three, and person.save would not attempt to autosave the failed feeling from the transaction. In an ideal world this would happen without additional db calls. Resetting the parent object seems pretty reasonable, but I assume this would constitute a breaking change.

[rails-bot]

This issue has been automatically marked as stale because it has not been commented on for at least
three months.

The resources of the Rails team are limited, and so we are asking for your help.

If you can still reproduce this error on the 4-2-stable, 4-1-stable branches or on master,
please reply with all of the information you have about it in order to keep the issue open.

Thank you for all your contributions.

[yoongkang]

I can confirm that this still occurs on master, but I don't think it's necessarily a bug. A transaction is supposed to rollback the state of the database upon an exception, but not the state of an object's instance data.

From the docs for Transactions:

Exceptions will force a ROLLBACK that returns the database to the state before the transaction began. Be aware, though, that the objects will not have their instance data returned to their pre-transactional state.

It appears that this behaviour has been around for a very long time, possibly since Rails was released.

[rails-bot]

This issue has been automatically closed because of inactivity.

If you can still reproduce this error on the 4-2-stable, 4-1-stable branches or on master,
please reply with all of the information you have about it in order to keep the issue open.

Thank you for all your contributions.