Forms shouldn't require whole Payment object instance

[artursmet]

Now when I want to render payment form (example with Stripe) I have to do something like this:

payment = Payment(variant='stripe', total=1, currency='USD')
payment_form = payment.get_form()

And it will return blank form. Sometimes we don't exactly know total amount, before payment form initialization, for example for single page checkouts.

Also there is a bug I think, when I want to initialize form with data:

payment_form = payment.get_form(request.POST or None)

It performs validation and save at this step ⚠️
https://github.com/mirumee/django-payments/blob/master/payments/stripe/__init__.py#L33

In my opinion get_form() method shouldn't try to validate the form and for sure it shouldn't save the form.

[patrys]

This is not trivial.

Some payment gateways require the form to be cryptographically signed using a hidden input. You need a payment object to do this.

Some payment gateways require that the form's action points to an external server. You can't put these inside a single page checkout.

get_form() is really a view. It either returns a form to display or tells you to redirect the user somewhere. It was not meant to be composed with other such views as there is no way to redirect a single browser to two separate resources. If you really want to call get_form() from a composite view, do not pass in data unless all other forms are valid and you've already saved them (so that get_form() can save whatever it wants and take over).