DateTimeField auto_now_add, auto_now & CreateView

[FoxMaSk]

Hi,
I think I spotted a bug with auto_now_add and auto_now in the models.

Here are the details to reproduce it

in a models.py

class Foobar(models.Model):
    created = models.DateTimeField(auto_now_add=True)

in a views.py

class FoobarCreateView(CreateView):
    model = Foobar
    fields = [ 'created' ]

will produce the error :

Unknown field(s) created specified for Foobar

To try to trakc the error, I put a "print fields" line 285 of the file django/forms/models.py in the class ModelFormMetaclass just before

            # make sure opts.fields doesn't specify an invalid field
            none_model_fields = [k for k, v in six.iteritems(fields) if not v]

which gives :

{u'created': None}

if I drop the auto_now_add from the model I get :

u'created': <django.forms.fields.DateTimeField object at 0x23bca10>

and get no error

The exact same behavior occurs with auto_now

Regards

[Tim Graham]

​As documented, "As currently implemented, setting auto_now or auto_now_add to True will cause the field to have editable=False and blank=True set." Since the field isn't editable, you can't add it to a form.

[FoxMaSk]

thank you - i didnt notice this subtility

[Daniel Hahler]

It can be useful to use editable=True to have it included in admin forms by default (where the whole form might be readonly then).

If the current behavior is kept it should probably throw a TypeError if editable=True or `blank=False´ is passed instead of silently overriding/ignoring it, which causes confusion e.g. with django-extensions (​https://github.com/django-extensions/django-extensions/issues/745).