nice one there
On Sun, Sep 11, 2022 at 3:36 PM David Sanders <shang.xiao.sand...@gmail.com>
wrote:
> Hi folks (and in particular Simon Charette),
>
> I had a bit of a gotcha moment when a custom unique constraint validation
> message disappeared when I added a condition to it. I won't raise a ticket
> for this because it looks intentional from the constraint validation PR,
> but I wanted to seek clarification and whether either some adjustment to
> the behaviour could be made or clarification in the docs.
>
> Here's a boiled down example:
>
> Validating models with UniqueConstraint usually groups errors by field
> name:
>
> class Test(Model):
> test = CharField(max_length=255)
>
> class Meta:
> constraints = [
> UniqueConstraint(fields=["test"], name="unique"),
> ]
>
> Test.objects.create(test="abc")
> test = Test(test="abc")
> test.validate_constraints()
> django.core.exceptions.ValidationError: {'test': ['Test with this Test
> already exists.']}
>
> However if a condition is added to the UniqueConstraint the validation
> error is categorised as a non-field error:
>
> class Test(Model):
> test = CharField(max_length=255)
>
> class Meta:
> constraints = [
> UniqueConstraint(fields=["test"], name="unique",
> condition=~Q(test="")),
> ]
>
> Test.objects.create(test="abc")
> test = Test(test="abc")
> test.validate_constraints()
> django.core.exceptions.ValidationError: {'__all__': ['Constraint “unique”
> is violated.']}
>
> This affects the way custom error messages are defined (eg forms
> error_messages dict vs constraint violation_error_message)
>
> This behaviour is defined in UniqueConstraint.validate() and looks to be
> intentional from this advice from Simon:
> https://github.com/django/django/pull/14625#issuecomment-897275721
>
> I was wondering what the rationale for that was? Would it be possible to
> make the behaviour consistent? And if not - would a PR to clarify how
> ValidationErrors are raised for constraints in the docs be welcomed?
>
> Cheers,
> David
>
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