Django Formset.is_valid() failing for extra forms

django, django-forms, formset

Solution

Thanks Carl, you led me to discover the root of my problem.

When creating a form with a choice field, which is required, we must set an initial value, otherwise the form will consider that field changed.

So for a form like this:

class SomeForm(forms.Form):

    A = 0
    B = 1
    C = 2
    D = 3

   choices = ((A, 'Aah'), (B, 'Baa'), (C, 'Caa'), (D, 'Daa'))

    # This is a required choice field
    pickme = forms.ChoiceField(choices=choices)

we do this:

pickme = forms.ChoiceField(choices=choices, initial=A)

Then when a formset checks the extra form it will see that pickme had an initial value of A, and it is A now as well, and will consider it unchanged.

Problem

In my Django application application I have a formset that is created from a simple (not-model) form, with the extra=1 (to allow javasript to add more forms later on). ``` class SomeForm(forms.Form): #some fields with required=False length = forms.IntegerField(required=False) # An example of one of the fields with choices i have A = 0 B = 1 C = 2 D = 3 choices = ((A, 'Aah'), (B, 'Baa'), (C, 'Caa'), (D, 'Daa')) # This is a required choice field pickme = forms.ChoiceField(choices=choices) SomeFormset = formset_factory(SomeForm, can_delete=True, extra=1) ``` Now, when I create and try to validate it in my view on the POST request: ``` my_formset = SomeFormset(request.POST, request.FILES) if(my_formset.is_valid()): # FAIL ``` it always fails the above check, if the extra rendered form is submitted empty. If I check for `form.changed_data` on the last empty extra form, I get the fields that have choices on them (like the pickme above). In other words, the formset is not smart enough to figure out that the empty submitted form should be ignored, when some choice fields are required.

Original source