id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
35374	UniqueConstraint (and potentially other constraints) validation is not run when using a form generated from `inlineformset_factory`	David Hang	nobody	"Due to how refactors in Django 4+ on how the unique validations are run for models and forms, an edge case has occured where in an inline form, `UniqueConstraint` checks which were previously run are now being skipped over and not returning validation errors, which then causing database integrity errors when the form is attempted to be saved.

Reproducible example:


{{{
from django.forms import inlineformset_factory
from django import forms
from django.db import models


class Farm(models.Model):
    name = models.CharField(max_length=255)


class Apple(models.Model):
    name = models.CharField(max_length=255)
    farm = models.ForeignKey(Farm, on_delete=models.CASCADE)

    class Meta:
        constraints = [
            models.UniqueConstraint(fields=[""name"", ""farm""], name=""unique_apple"")
        ]


class AppleForm(forms.ModelForm):
    class Meta:
        model = Apple

        fields = [""name"", ""farm""]


big_farm = Farm.objects.create(name=""Big Farm"")
best_apple = Apple.objects.create(name=""Best Apple"", farm=big_farm)

AppleFormSet = inlineformset_factory(Farm, Apple, AppleForm)

data = {
    ""apple_set-TOTAL_FORMS"": ""2"",
    ""apple_set-INITIAL_FORMS"": ""0"",
    ""apple_set-0-name"": ""Best Apple"",
    ""apple_set-0-farm"": big_farm.pk,
}

formset = AppleFormSet(data, instance=big_farm)

print(formset.is_valid())
print(formset.errors)

formset.save()

}}}


{{{
IntegrityError: duplicate key value violates unique constraint ""unique_apple""
DETAIL:  Key (name, farm_id)=(Best Apple, 3) already exists.
}}}

In normal forms, and formsets, the validation does run correctly. This issue caused by https://github.com/django/django/blob/42bc81b1b6471c4fe364bc32b9dec180908e577e/django/forms/models.py#L486


{{{

        # Foreign Keys being used to represent inline relationships
        # are excluded from basic field value validation. This is for two
        # reasons: firstly, the value may not be supplied (#12507; the
        # case of providing new values to the admin); secondly the
        # object being referred to may not yet fully exist (#12749).
        # However, these fields *must* be included in uniqueness checks,
        # so this can't be part of _get_validation_exclusions().
        for name, field in self.fields.items():
            if isinstance(field, InlineForeignKeyField):
                exclude.add(name)
}}}

"	Bug	closed	Forms		Normal	invalid		David Hang	Unreviewed	0	0	0	0	0	0