Model with GeneratedField and ForeignKey raises an error on save().

[Deb Kumar Das]

When using GeneratedField column along with a ForeignKey column, getting error while saving.
The below model throws error while saving data from admin panel.

class Square(models.Model):
    side = models.IntegerField()
    area = models.GeneratedField(
        expression=F("side") * F("side"),
        output_field=models.BigIntegerField(),
        db_persist=True,
    )
    user = models.ForeignKey(get_user_model(), on_delete=models.CASCADE)

Throws the below error

Cannot force an update in save() with no primary key.

attached error screenshot

[Mariusz Felisiak]

Good catch!

Regression in f333e3513e8bdf5ffeb6eeb63021c230082e6f95.

[Simon Charette]

The patch will need some improvements as we must consider that generated fields can also be deferred. We'll likely want to add tests for generated field deferral as well.

[Mariusz Felisiak <felisiak.mariusz@…>]

In b287af5d:

Fixed #35019 -- Fixed save() on models with both GeneratedFields and ForeignKeys.

Thanks Deb Kumar Das for the report.

Regression in f333e3513e8bdf5ffeb6eeb63021c230082e6f95.

[Mariusz Felisiak <felisiak.mariusz@…>]

In 03af8fb:

[5.0.x] Fixed #35019 -- Fixed save() on models with both GeneratedFields and ForeignKeys.

Thanks Deb Kumar Das for the report.

Regression in f333e3513e8bdf5ffeb6eeb63021c230082e6f95.

Backport of b287af5dc954628d4b336aefc5027b2edceee64b from main

[Deb Kumar Das]

Thanks @Mariusz Felisiak and all the Django team, for a quick response and fix.