how to build a validator in django for formsets when text is empty?

Question

What is the best way to build a validator that checks for an empty value (i.e. empty string) in a formset using django.forms.formsets.formset_factory ?

What I'm using now is, first the forms.py:

from django import forms
from django.core.exceptions import ValidationError
from django.core.validators import URLValidator

class UrlsForm(forms.Form):
    def validate_contains_something(value):
        if value == " ":
            raise ValidationError(u'(link)value: "%s" is empty' % value)

    my_url = forms.URLField(required=True,
                            max_length=200,
                            label = '',
                            widget=forms.TextInput(
                                attrs=
                                {
                                    'placeholder':'< enter url here >',
                                    'size':75,
                                    'class':'data',
                                }),
                            validators=[validate_contains_something,
                                        URLValidator,]
                           )

Then shell commands:

from django.forms.formsets import formset_factory
from doc_select_new.forms import UrlsForm
from django.forms.formsets import BaseFormSet
UrlsFormSet = formset_factory(UrlsForm, formset=BaseFormSet, validate_max=True)

data = { 'form-INITIAL_FORMS': '0',
         'form-MAX_NUM_FORMS': '1000',
         'form-TOTAL_FORMS': '3',
         'form-0-my_url': '',
         'form-1-my_url': 'http://www.google.com/',
         'form-2-my_url': 'https://www.djangoproject.com/',
}
formset = UrlsFormSet(data)
valid_or_not = formset.is_valid()

Which gives no error for form-0-my_url. What am I doing wrong? Or how can you let the validator for checking '' go wrong and deliver an error?

Answer 1

Extra forms (dynamically added ones) can be empty in django. In shell this is simulated by 'form-INITIAL_FORMS' data parameter - as it's 0, django thinks all the 3 forms are extra forms. Setting it to 1 will tell django to validate the first form.

This behavior is due to empty_permitted form argument. So another way is to set it to False. It will force the validation for all the forms:

class UrlsForm(forms.Form):

    def __init__(self, *args, **kwargs):
        super(UrlsForm, self).__init__(*args, **kwargs)
        self.empty_permitted = False