Broken reverse FK behaviour in Django 4.1

[amureki]

• https://docs.djangoproject.com/en/4.1/releases/4.1/#reverse-foreign-key-changes-for-unsaved-model-instances
• Fixed #19580 -- Unified behavior of reverse foreign key and many-to-many relations for unsaved instances. django/django#15318

[amureki]

I'd close this for now, as I did not receive any feedback from users regarding this change in Django 4.1.
It might still appear, and then we'll think on the way we tackle this.

[jefftriplett]

Sorry to delay. I am seeing this too in a few projects now that I have time to dig back in.

This is the pattern I'm seeing it with:

job = JobSerializer(
    baker.prepare(
        "jobs.Job",
        company=baker.make("companies.Company"),
        employee=baker.make("companies.Employee"),
    )
).data

Generates:

> ValueError: 'Job' instance needs to have a primary key value before this relationship can be used.

[amureki]

@jefftriplett sorry Jeff, I missed your reply. Thanks for the report!

May I assume your model structure looks like the following? Just to make sure I am not missing any specifics:

class Job(models.Model):
    company = models.ForeignKey("companies.Company")
    employee = models.ForeignKey("companies.Employee")

Did you find a way around it? I am honestly can't think of a good way yet of solving it that can comply with changes in Django.

[syphar]

@amureki I was working on upgrading to django 4.1, and we are potentially hitting the same issue (I think), but a little different:

class Parameters(models.Model): 
     something = models.IntegerField() 

class Opportunity(models.Model):
     parameters = models.OneToOneField(Parameters, blank=True, null=True)

and then this fails:

baker.make_recipe("opportunity.Opportunity", parameters=p)

Which is strange, this this is make_recipe, not prepare_recipe, right?

[syphar]

If needed I can try to build a minimal example how to reproduce this

[amureki]

If needed I can try to build a minimal example how to reproduce this

That would be wonderful! It is not clear for me, how p object is created and how does the recipe looks like.
I tried something to your example, but was unable to reproduce the issue:

class Person(models.Model):
    age = models.IntegerField()

class LonelyPerson(models.Model):
    only_friend = models.OneToOneField(Person, on_delete=models.CASCADE, blank=True, null=True)

def test_default_behaviour_for_one_to_one():
    only_friend = baker.make(models.Person)
    lonely_person = baker.make(models.LonelyPerson, only_friend=only_friend)

    assert lonely_person.pk
    assert lonely_person.only_friend.pk

def test_default_behaviour_for_one_to_one__prepare():
    only_friend = baker.prepare(models.Person)
    lonely_person = baker.prepare(models.LonelyPerson, only_friend=only_friend)

    assert not lonely_person.pk
    assert not lonely_person.only_friend.pk

[syphar]

@amureki forget my comment above, thank you for investing the time.

I was stupid and the actual problem wasn't related to model-bakery

[amureki]

@amureki forget my comment above, thank you for investing the time.

I was stupid and the actual problem wasn't related to model-bakery

No, there is nothing wrong with that, it was good to check O2O relations anyway. Please tell me if you'd stumble upon that issue later, and good luck with your Django 4.1 upgrade! 🤞