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

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()

The simplest way to call the full_clean method is just to override the save method in your model:

class YourModel(models.Model):
    ...  
    
    def save(self, *args, **kwargs):
        self.full_clean()
        return super(YourModel, self).save(*args, **kwargs)