ModelForm: override default field attributes

[Rolando Espinoza La fuente]

The common way to alter fields attributes seems to be overriding ModelForm __init__, like:

class FooForm(forms.ModelForm):
    def __init__(self, *args, **kwargs):
        super(FooForm, self).__init__(*args, **kwargs)
        self['field'].attr = "foo"

In #11925 was added the widget Meta attribute. In the same way could be provided a mechanism to override default field attributes.

The patch attached adds support for Meta.fields_attrs. For example:

class Foo(models.Model):
    user = models.ForeignKey(User)

class FooForm(forms.ModelForm):
    """Renders a select widget with "-----" as first option and display all users"""
    class Meta:
        model = Foo

class StaffFooForm(forms.ModelForm):
    """Renders a select widget without empty option and only display staff users"""
    class Meta:
        model = Foo
        fields_attrs = {
            'user': {
                'empty_label': None,
                'queryset': User.objects.filter(is_staff=True),
            },
        }

[Petr Marhoun <petr.marhoun@…>]

Added another patch for the same feature - I implemented it independently (and found this ticket later). My patch has tests and use different name for proposed feature (fields_kwargs instead fields_attrs - but it is not important for me and I do not know what is better).

There is also some motivation here:
​http://code.djangoproject.com/wiki/ImprovementsForDjangoForms#Modelfieldswithnot-defaultvalues

I think also there is a problem in the original patch - function should not have dictionary as default argument because dictionary is mutable.

[asenchi]

Tested 'fields-kwargs.diff', patch applied cleanly all tests ran. Test should be rewritten into unittests. Also needs documentation.

[asenchi]

Actually this looks to have been implemented in 1.2:
​http://docs.djangoproject.com/en/1.2/topics/forms/modelforms/#overriding-the-default-field-types-or-widgets

[Petr Marhoun <petr.marhoun@…>]

Ticket reopened: New meta attribute "widgets" was really implemented in 1.2, but it is only for overriding of one attribute "widget". This ticket is about overriding of general attributes (for example label, required or something specific for given field) without total replacement of the field.

Added new version of patch which could be applied against trunk. And it is again with doctests - model_forms tests have not been ported to unittest yet.

[Aymeric Augustin]

Change UI/UX from NULL to False.

[Aymeric Augustin]

Change Easy pickings from NULL to False.

[Jacob]

There's a limit of what attributes can do; at some point you're going to have to override __init__. Widgets are common and annoying enough to have a special-case, but for everything else we should encourage people to override __init__ rather than adding hooks like this.