id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
14234	Validation bug when using ModelForms	David Reynolds	Jeremy Dunck	"I am running into a validation problem with !ModelForms - here is a quick summary of what is happening

Take a simple model - here we call `Model`.`full_clean` as part of the custom save method to enforce the validation:

{{{
from django.db import models

class Stuff(models.Model):
   """"""(Stuff description)""""""
   name = models.CharField(max_length=100)
   age = models.IntegerField()
   description = models.TextField(blank=True)

   def __unicode__(self):
       return self.name

   def save(self, *args, **kwargs):
       self.full_clean()
       return super(Stuff, self).save(*args, **kwargs)
}}}
Simple !ModelForm for the above - nothing unusual here:

{{{
from django import forms


class StuffModelForm(forms.ModelForm):

   class Meta:
       model = Stuff

# Instantiate the form with some data
form = StuffModelForm({
   'name': 'Fred',
   'age': '56',
   'description': 'Old Fred is 57',
})

# Check the form is valid
if form.is_valid():
   obj = form.save(commit=False) # save but don't commit
   obj.age = 27 # Change the age
   obj.save() # Do a full save of the object

   obj.name = 'Ted' # Change the name
   obj.save() # Attempt to update the db record

# you get this error:
ValidationError: {'id': [u'Stuff with this ID already exists.']}
}}}

This happens because the `ModelForm` sets `ModelForm`.`instance`.`_adding` to `True` and never cleans it up. This is then tested for in `Model`.`_perform_unique_checks`  and the uniqueness checks are executed if it is set to `True` which it always is after calling `ModelForm`.`save`()

"		closed	Forms	1.2		fixed			Accepted	1	0	0	0	0	0