custom formset validation documentation is incomplete

[splatEric <mike@…>]

The example for performing custom formset validation is incomplete. It does not take into account deleted forms, or empty forms for checking the unique titles constraint. It should read something along the lines of (changes highlighted by *>):

>>> class BaseArticleFormSet(BaseFormSet):
...     def clean(self):
...         """Checks that no two articles have the same title."""
...         if any(self.errors):
...             # Don't bother validating the formset unless each form is valid on its own
...             return
...         titles = []
...         for i in range(0, self.total_form_count()):
*>             if self.can_delete and self._should_delete_form(form):
*>                continue
...             form = self.forms[i]
*>             if 'title' in form.cleaned_data:
...                 title = form.cleaned_data['title']
...                 if title in titles:
...                     raise forms.ValidationError, "Articles in a set must have distinct titles."
...                 titles.append(title)

[Gabriel Hurley]

Accepted. For future reference, the file in question is docs/topics/forms/formsets/.

[leonelfreire]

Hi,

I think there's an "error" with the above suggestion too. self.errors will contain the errors of all forms (even if the form is marked for deletion). Supposing all NOT DELETED forms are valid, if some deleted form is in an invalid state, the code:

if any(self.errors):
	return

will make the "clean" method return too soon, avoiding the execution of the validation of the NOT DELETED forms.

AFAIK, formset.is_valid() can be True, even if formset.errors contains forms errors (from deleted forms).

In my case, I did something like:

(...)
def clean(self)
	if self.is_valid():
		try:
			# Get only the forms not marked for deletion
			cleaned_forms = list(set(self.forms) - set(self.deleted_forms))
		except AttributError: # There're no forms marked for deletion (no self.deleted_forms)
			cleaned_forms = self.forms
	
		# validate logic with cleaned_forms
		(...)

If there's a better way to do this, let me know.

[Aymeric Augustin]

Change UI/UX from NULL to False.

[Aymeric Augustin]

Change Easy pickings from NULL to False.

[Mariusz Felisiak]

​PR

[Mariusz Felisiak <felisiak.mariusz@…>]

In d610521b:

Fixed #14009 -- Fixed custom formset validation example in docs.

[Mariusz Felisiak <felisiak.mariusz@…>]

In c0dc49a7:

[2.2.x] Fixed #14009 -- Fixed custom formset validation example in docs.

Backport of d610521bffe9d44a070ebe3a719b474aff6d3d1e from master