MinValueValidator/MaxValueValidator not forwarded to form field for ModelForm

[Sergei Maertens]

I just ran into a possible enhancement.

Consider the following model:

DEFAULT_RATING = 50
MAX_RATING = 100
MIN_RATING = 0


class KitReviewPropertyRating(models.Model):
    """
    Represents properties for a kit review rated on a scale from MIN_RATING to MAX_RATING
    """
    kit_review = models.ForeignKey('KitReview', related_name='ratings')
    prop = models.ForeignKey('KitReviewProperty')
    rating = models.PositiveSmallIntegerField(
        _('rating'), default=DEFAULT_RATING,
        validators=[MinValueValidator(MIN_RATING), MaxValueValidator(MAX_RATING)]
    )

and the matching ModelForm:

from django.forms.widgets import NumberInput


class RangeInput(NumberInput):
    input_type = 'range'


class KitReviePropertyRatingForm(forms.ModelForm):

    class Meta:
        model = KitReviewPropertyRating
        fields = ('id', 'prop', 'rating')
        widgets = {
            'rating': RangeInput(attrs={'max': MAX_RATING})
        }

As you can see, I have to specify the max widget attribute manually, otherwise the html input looks like this: <input type="range" name="rating" value="50" min="0">, instead of the expected <input type="range" name="rating" value="50" min="0" max="100">. I had expected the Min/MaxValueValidator to be 'forwarded' to the form field (via IntegerField.formfield method), but no such thing happens. #26786 does add the validators on the model level, based on the db connection used and the limits there, and only if no such validators were present yet.

I'd like to make it so that Min/MaxValueValidators are translated into min_value/max_value defaults for the IntegerField.formfield method, this would be more in line with the expected output and reduce the need to repeat yourself.

[Tim Graham]

I'm wary of the additional complexity, but can't say that the request is unreasonable.

[Tim Graham]

Comments for improvement on the PR (and some failing tests to be fixed).

[Mariusz Felisiak]

The proposed solution has some side-effects. We should reach a wider audience and consensus on DevelopersMailingList before moving this forward.

[Claude Paroz]

#25594 might be related.