ModelForms do not recognize DateTimeFields with auto_now=True

[Jerome Leclanche]

When creating a model with a DateTimeField(auto_now=True), the field is not present in a ModelForm (affects the django admin).

>>> from django.db.models import *
>>> from django.forms import ModelForm
>>> class Test(Model):
...  pub_date = DateTimeField(auto_now=True)
...  class Meta:
...   app_label = "editor"
... 
>>> class TestForm(ModelForm):
...  class Meta:                                                                                                                                                                                                                            
...   model = Test                                                                                                                                                                                                                          
... 
>>> TestForm()
<TestForm object at 0x2603890>
>>> TestForm().fields
{}

Removing auto_now lets the field be recognized. This is a regression since django 0.9 if that's worth anything.

[Anssi Kääriäinen]

It seems this is intentional. The user is not supposed to edit the field, and thus it is not present in the form. It seems you can display the field with using readonly_fields. ​http://stackoverflow.com/questions/10033422/cant-display-datefield-on-form-with-auto-now-true

[Jerome Leclanche]

In that case, it's something worth mentioning in the docs (either in the ModelForm or the DateTimeField or both), it was the source of a lot of pain and work trying to figure out what was going on, especially as it's a regression.

[Anssi Kääriäinen]

It kind of is: the auto_now documentation says that setting it to true implies editable=False, and editable is documented as:

If False, the field will not be editable in the admin or via forms automatically generated from the model class. Default is True.

Now, the editable documentation could perhaps be a little cleaner - it doesn't explicitly state the field is totally removed from the form, just that it is not editable.

As for regressions, I don't think there are any guarantees for pre 1.0 versions.

[Ryan C. Schwiebert]

The datetime field I'm using has editable=True and the ModelForm fails for the same reason. For insurance I also put auto_add=False and auto_now_add =False. Same problem.

Maybe the above comments explain the problem, but it doesn't explain how to overcome it.