ManagementForm exception in case of bad prefix should be easier to understand

[Karel]

If user adds multiple formsets with prefixes, and specifies the prefix incorrectly when binding the form and validating:

some_formset = SomeFormSet(request.POST, 'articles')

instead of:

some_formset = SomeFormSet(request.POST, prefix='articles') 

Django "suppresses" the original exception and raises only relatively unhelpful "ManagementForm data is missing or has been tampered with".

In file django/forms/formsets.py, line 57:

  54. if self.data or self.files:
  55.     form = ManagementForm(self.data, auto_id=self.auto_id, prefix=self.prefix)
  56.     if not form.is_valid():
  57.         raise ValidationError('ManagementForm data is missing or has been tampered with') 

Suggestion: include form._errors in output, because for such a small bug in code, it can take a really long time find it.

{'INITIAL_FORMS': [u'This field is required.'],
 'MAX_NUM_FORMS': [u'This field is required.'],
 'TOTAL_FORMS': [u'This field is required.']}

[stherrien]

validation error with _errors included

[Russell Keith-Magee]

Not sure I completely agree with the suggested fix, but yes -- the error on failure of the management form could be a little more helpful, at the very least naming the field that is missing or invalid.

[Julien Phalip]

Patch would need improvement as per Russell's comment. Also needs tests.

[Aymeric Augustin]

Change UI/UX from NULL to False.

[Aymeric Augustin]

Change Easy pickings from NULL to False.

[Manav Agarwal]

We may change the code from :

raise ValidationError(
                    _('ManagementForm data is missing or has been tampered with'),
                    code='missing_management_form',
                )

to something like:

raise ValidationError(
                    _('ManagementForm data is missing or has been tampered with %s' % form._errors),
                    code='missing_management_form',
                )

Approvals please.

[Jacob Walls]

​PR

[Jacob Walls]

On second thought I suppose it’s a bit early for the needs tests flag since no one has supplied a review.

[Mariusz Felisiak <felisiak.mariusz@…>]

In 096b14f0:

Fixed #13060 -- Improved error message when ManagementForm data is missing.