Fixed #12901. Exclude overridden form fields from model field validation. Thanks, Honza Král.

            # adding these values to the model after form validation.

            if field not in self.fields:

                exclude.append(f.name)

            # Don't perform model validation on fields that were defined

            # manually on the form and excluded via the ModelForm's Meta

            # class. See #12901.

            elif self._meta.fields and field not in self._meta.fields:

                exclude.append(f.name)

            # Exclude fields that failed form validation. There's no need for

            # the model fields to validate them as well.

            elif field in self._errors.keys():

                exclude.append(f.name)

            # Exclude empty fields that are not required by the form. The

            # underlying model field may be required, so this keeps the model

            # field from raising that error.

    def add_fields(self, form, index):

        super(BaseInlineFormSet, self).add_fields(form, index)

        if self._pk_field == self.fk:

            form.fields[self._pk_field.name] = InlineForeignKeyField(self.instance, pk_field=True)

            name = self._pk_field.name

            kwargs = {'pk_field': True}

        else:

            # The foreign key field might not be on the form, so we poke at the

            # Model field to get the label, since we need that for error messages.

            name = self.fk.name

            kwargs = {

                'label': getattr(form.fields.get(self.fk.name), 'label', capfirst(self.fk.verbose_name))

                'label': getattr(form.fields.get(name), 'label', capfirst(self.fk.verbose_name))

            }

            if self.fk.rel.field_name != self.fk.rel.to._meta.pk.name:

                kwargs['to_field'] = self.fk.rel.field_name

            form.fields[self.fk.name] = InlineForeignKeyField(self.instance, **kwargs)

        form.fields[name] = InlineForeignKeyField(self.instance, **kwargs)

        # Add the generated field to form._meta.fields if it's defined to make

        # sure validation isn't skipped on that field.

        if form._meta.fields:

            if isinstance(form._meta.fields, tuple):

                form._meta.fields = list(form._meta.fields)

            form._meta.fields.append(self.fk.name)

    def get_unique_error_message(self, unique_check):

        unique_check = [field for field in unique_check if field != self.fk.name]

from django.test import TestCase

from django import forms

from models import Category

class IncompleteCategoryForm(forms.ModelForm):

    """

    A form that replaces the model's url field with a custom one. This should

    prevent the model field's validation from being called.

    """

    url = forms.CharField(required=False)

    class Meta:

        fields = ('name', 'slug')

        model = Category

class ValidationTest(TestCase):

    def test_validates_with_replaced_field(self):

        form = IncompleteCategoryForm(data={'name': 'some name', 'slug': 'some-slug'})

        assert form.is_valid()