Natural keys for nullable foreign keys

[Martin Beroiz]

I found that if a fixture has a model with a nullable foreign key (FK) to a model with natural keys, loaddata fails to load the first object.
For example, slightly modifying the docs example:

class PersonManager(models.Manager):
    def get_by_natural_key(self, name):
        return self.get(name=name)

class Person(models.Model):
    name = models.CharField(max_length=100, unique=True)
    objects = PersonManager()

    def natural_key(self):
            return (self.name,)

class Book(models.Model):
    name = models.CharField(max_length=100)
    author = models.ForeignKey(Person, on_delete=models.CASCADE, null=True)

(notice the null=True addition to Book)

Then this fixture will fail when attempting to load with loaddata

[
  {
    "model": "myapp.book",
    "fields": {
      "name": "I Ching",
      "author": null,
    }
  },
]

Notice that "author": [null] in the fixture does not fix it either, since it will pass None to the manager's get_by_natural_key. Returning None from get_by_natural_key doesn't help either.

If this is a feature, and models with natural keys can't ever be referenced by other models with a _nullable_ FK to them, I think it should probably be explicit in the documentation.

[Mariusz Felisiak]

Thanks for the ticket, however "author": null works for me (checked on Django 4.2.2). You can try to use one of support channels when folks should help you debug.