Django form returns is_valid() = False and no errors

Question

I have simple view in django app, which I want to show only when one of the forms is valid. I have something like:

@login_required
@require_role('admin')
def new_package(request):
    invoicing_data_form = InvoicingDataForm(instance=request.user.account.company.invoicingdata)
    if invoicing_data_form.is_valid():
        # all here
        return HttpResponse('Form valid')
    else:
        logger.info("Form invalid")
        return HttpResponse(json.dumps(invoicing_data_form.errors)

I always get log info message that form is invalid, however, I get nothing in

invoicing_data_form.errors

It is very strange, because I am validating this form in other view using user input data and it works just fine. Any idea?

EDIT: Just for clarification. I am not requesting any data from user in this form. I am using this form to validate some model instance (this form is subclassing from ModelForm).

Leger

first of all, you need to check for form post. – Riehl

Why? I am not sending any data via POST. I just want to validate form (ModelForm) using model instance. – Leger

Answer 1

That's because you're not "feeding" your form.

Do this:

invoicing_data_form = InvoicingDataForm(instance=invoice, data=request.POST or None)

Gegenschein

I've added this, but form is still invalid :( – Leger

yes but you should be able to inspect the errors now – Acree

you need to check request.POST, if it's empty replace it with something else. If there is no data, the form is unbound and there won't be any error showing. – Acree

Using data=request.POST or None will cause that invoicing_data_form.is_bound will always be False. When I change it, for example to data={} then form is bound, but its not validating (because data dict is empty ;)) – Leger

well I couldn't know without your edit. Anyway the answer remains the same, fill up data ;) – Acree

I ended up with something like: invoicing_data_form = InvoicingDataForm(data=request.user.account.company.invoicingdata.__dict__, instance=request.user.account.company.invoicingdata) – Leger

Answer 2

You have an unbound form. https://docs.djangoproject.com/en/1.7/ref/forms/api/#bound-and-unbound-forms

A Form instance is either bound to a set of data, or unbound.

If it’s bound to a set of data, it’s capable of validating that data and rendering the form as HTML with the data displayed in the HTML.

If it’s unbound, it cannot do validation (because there’s no data to validate!), but it can still render the blank form as HTML.

To bind data to a form, pass the data as a dictionary as the first parameter to your Form class constructor:

invoicing_data_form = InvoicingDataForm(request.POST or None, instance=invoice)

Crinite

In this view I want to only validate form, I am not requesting any data from user. Thats why I am providing object instance to the form (which is ModelForm class instance). Are you sure thats I need to provide data? Even if so, when I added this, I am still getting form invalid message, and there is no errors at all – Leger

Thankyou thankyou thankyou – Deceit

Answer 3

If you're already giving request.POST to your form using request.POST or None, but it's still invalid without errors, check that there isn't any redirect going on. A redirect loses your POST data and your form will be invalid with no errors because it's unbound.

Crimple

This answer helped me find my solution. In my case, I was overriding def __init__(self, request): in the form class to add widget/field attributes, but forgetting to pass the request through the super call super(Form, self).__init__(request). Same idea, I was losing the request object prior to calling is_valid(). – Goggin

Answer 4

I got this for AuthenticationForm which needs AuthenticationForm(None, request.POST) see Using AuthenticationForm in Django

Carding

Answer 5

I want to expand on the answer by @yuji-tomita-tomita

I typically use a CBV approach in Django, and how I'm handling forms:

def post(self, request, *args, **kwargs):
    form = self.get_form()
    if form.is_valid():
        # do things

Reading the source code I noticed that self.get_form() using get_form_kwargs(self) to populate the form with request.POST, thus getting bound to data. So if you're overloading it like I did:

def get_form_kwargs(self):
    company = self.get_company()
    return {"company": company}

Make sure to call the super(), and it will finally work:

def get_form_kwargs(self):
    company = self.get_company()
    kwargs = super().get_form_kwargs()
    kwargs.update({"company": company})
    return kwargs

Ritter