#24787: ModelForm validation crashes for ForeignKey field with blank=True and
null=False
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Reporter: mssnlayam | Owner: nobody
Type: Uncategorized | Status: new
Component: Uncategorized | Version: 1.8
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 0
Easy pickings: 0 | UI/UX: 0
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Here's my model code
{{{
from django.db import models
from django.contrib.auth.models import User
class MyModel(models.Model):
user = models.ForeignKey(User, blank=True, null=False)
def clean(self):
defaultuser = User.objects.first()
if not defaultuser:
raise ValueError('Need at least one user')
self.user = defaultuser
return super(MyModel, self).clean()
}}}
Here's my code where I create and initialize a `ModelForm`
{{{
from __future__ import print_function
import django
django.setup()
from myapp.models import MyModel
from django.forms.models import modelform_factory
MyForm = modelform_factory(MyModel, fields=('user', ))
myform = MyForm({})
print(myform.is_valid())
}}}
Here's the crash on running the above program:
{{{
Traceback (most recent call last):
File "a.py", line 10, in <module>
print myform.is_valid()
File "/home/vagrant/bookshelf.git/my-env/local/lib/python2.7/site-
packages/django/forms/forms.py", line 184, in is_valid
return self.is_bound and not self.errors
File "/home/vagrant/bookshelf.git/my-env/local/lib/python2.7/site-
packages/django/forms/forms.py", line 176, in errors
self.full_clean()
File "/home/vagrant/bookshelf.git/my-env/local/lib/python2.7/site-
packages/django/forms/forms.py", line 394, in full_clean
self._post_clean()
File "/home/vagrant/bookshelf.git/my-env/local/lib/python2.7/site-
packages/django/forms/models.py", line 427, in _post_clean
self.instance = construct_instance(self, self.instance, opts.fields,
construct_instance_exclude)
File "/home/vagrant/bookshelf.git/my-env/local/lib/python2.7/site-
packages/django/forms/models.py", line 62, in construct_instance
f.save_form_data(instance, cleaned_data[f.name])
File "/home/vagrant/bookshelf.git/my-env/local/lib/python2.7/site-
packages/django/db/models/fields/__init__.py", line 874, in save_form_data
setattr(instance, self.name, data)
File "/home/vagrant/bookshelf.git/my-env/local/lib/python2.7/site-
packages/django/db/models/fields/related.py", line 619, in __set__
(instance._meta.object_name, self.field.name)
ValueError: Cannot assign None: "MyModel.user" does not allow null values.
}}}
What's the right way to support a `ForeignKey` with `blank=True` and
`null=False`? Form validation does not even raise `ValidationError`. It
simply crashes.
Had a conversation with @apollo13 on IRC who said that this is a bug to be
reported.
--
Ticket URL: <https://code.djangoproject.com/ticket/24787>
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