Why doesn't django's model.save() call full_clean()?

I'm just curious if anyone knows if there's good reason why django's orm doesn't call 'full_clean' on a model unless it is being saved as part of a model form.

Note that full_clean() will not be called automatically when you call your model’s save() method. You’ll need to call it manually when you want to run one-step model validation for your own manually created models. django's full clean doc

(NOTE: quote updated for Django 1.6... previous django docs had a caveat about ModelForms as well.)

Are there good reasons why people wouldn't want this behavior? I'd think if you took the time to add validation to a model, you'd want that validation run every time the model is saved.

I know how to get everything to work properly, I'm just looking for an explanation.

AFAIK, this is because of backwards compatibility. There are also problems with ModelForms with excluded fields, models with default values, pre_save() signals, etc.

Sources you might be intrested in:

• http://code.djangoproject.com/ticket/13100
• http://groups.google.com/group/django-developers/browse_frm/thread/b888734b05878f87

Because of the compatibility considering, the auto clean on save is not enabled in django kernel.

If we are starting a new project and want the default save method on Model could clean automatically, we can use the following signal to do clean before every model was saved.

from django.dispatch import receiver
from django.db.models.signals import pre_save, post_save

@receiver(pre_save)
def pre_save_handler(sender, instance, *args, **kwargs):
    instance.full_clean()