Error Creating a Model with a GeneratedField

[Jason Christa]

class ProjectHealth(models.Model):
    class HEALTH(models.TextChoices):
        GREEN = "green", "Green"
        YELLOW = "yellow", "Yellow"
        RED = "red", "Red"
        NA = "not applicable", "N/A"


    project = models.ForeignKey("Project", on_delete=models.CASCADE)
    health = models.CharField(
        choices=HEALTH.choices, max_length=50, default=HEALTH.GREEN, db_default=HEALTH.GREEN
    )
    health_value = models.GeneratedField(
        expression=Case(
            When(health=HEALTH.GREEN, then=Value(1)),
            When(health=HEALTH.YELLOW, then=Value(2)),
            When(health=HEALTH.RED, then=Value(3)),
            default=Value(0),
        ),
        output_field=models.IntegerField(),
        db_persist=True,
    )

In this simple model when I try to create a new ProjectHealth record, health_value is set as a deferred field in base save(). This causes the rest of the save process to treat this as an update instead of an insert. It ends with the error Cannot force an update in save() with no primary key.

[Simon Charette]

Duplicate of #35019, will be fixed in Django 5.0.1 expected to be released on Jan 2nd.