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
16110	GeometryField does not allow setting blank=True and null=False	Paul Winkler	nobody	"Sometimes you want to populate a required field's missing value with a value generated eg. from other form fields.
One common idiom for doing this is to have SomeField(blank=True, null=False) and provide the missing value in eg. the Form's clean() method.

For example, I've done variations on this a lot:
{{{
class Foo(Model):
    geom = PointField(blank=True, null=False)
    address = CharField(max_length=100)
    class Meta:
        app_label = 'myblock' # or whatever,

class FooForm(ModelForm):
    class Meta:
        model = Foo

    def clean(self):
        geom = self.cleaned_data.get('geom')
        if not geom:
            self.cleaned_data['geom'] = geocode(self.cleaned_data['address'])
        return super(FooForm, self).clean()
}}}

But with a GeometryField, that doesn't work, because of these lines in
GeometryField.clean() in django/contrib/gis/forms/fields.py :

{{{
        if not value:
            if self.null and not self.required:
                # The geometry column allows NULL and is not required.
                return None
            else:
                raise forms.ValidationError(self.error_messages['no_geom'])

}}}

Effectively, this makes blank=True meaningless.

As far as I know, GeometryField is the only FormField shipped with django that behaves this way.
This is surprising and inconsistent, and leads to odd workarounds to convince forms.GeometryField to leave you alone. Eg. hacking a ModelAdmin's  formfield_for_dbfield() like so:
{{{
    def formfield_for_dbfield(self, db_field, **kwargs):
        if db_field.name == 'geom':
            kwargs['required'] = False
            kwargs['null'] = True
        return super(MyModelAdmin, self).formfield_for_dbfield(db_field, **kwargs)

}}}

Fixing this is trivial. Patch attached."	Bug	closed	GIS	dev	Normal	fixed			Accepted	1	0	0	0	0	0