id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
13249	Feature request: ModelForm validation error handling after commit=False	Oroku Saki	nobody	"For lack of a good explanation, I'll include an example first:

{{{
#First, the models and forms used in example:

class Account(models.Model):
    subdomain = SubdomainField(max_length=25, unique=True)


class Administrator(models.Model):
    account = models.ForeignKey(Account, related_name='administrators')
    username = LowerAlphanumericField(max_length=50)
    email = models.EmailField()
    
    class Meta:
        unique_together = (('account', 'username'), ('account', 'email'))


class AdministratorForm(ModelForm):
    class Meta:
        model = Administrator
        exclude = ('account',)

}}}

And, here's the example usage that breaks:

{{{
#views.py

def create_administrator(request):
    from django.db.utils import IntegrityError
    from myproject.apps.account.forms import AdministratorForm
    if request.method == 'POST':
        form = AdministratorForm(request.POST)
        if form.is_valid():
            instance = form.save(commit=False)
            instance.account = request.account  # ``account`` is attached to ``request`` in custom middleware.
            instance.save()
            # What happens if there is an error here such as IntegrityError with one of the 2 unique_together fields ('username', and 'email').
            # You cannot tell which field failed the ``unique_together`` test. validate_unique skips over the excluded fields in the form.
            #
            # You could run instance.full_clean() first and catch ValidationErrors and handle them manually, but this would not be very DRY after about 3 views.
            # I don't know what the new version would be like, but I can imagine a way to validate the instance and then add the errors into the form again or something.
}}}

I probably made this very confusing, but basically there is no way to use commit=False and still use ModelForm's built-in validation conveniences."	Bug	closed	Forms	dev	Normal	duplicate			Design decision needed	0	0	0	0	0	0