#25349: ModelForm regression when setting None into a ForeignKey
-------------------------------+--------------------
Reporter: jpaulett | Owner: nobody
Type: Uncategorized | Status: new
Component: Forms | Version: 1.8
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------+--------------------
It appears that when using a ModelForm to "unset" a non-required foreign
key field, Django 1.8 no longer will set the foreign key to None when
saving the ModelForm, and the prior value for the ForeignKey remains.
In practice, imagine a form where users can pick a category to assign to
the instance, but can un-assign its category by picking the empty_label
value in the <select>.
The behaviour worked previously in Django, including 1.6 and 1.7.9, but
appears when testing against Django 1.8.5. I have also tested the
stable/1.8.x and master branches on github, which still show the issue. I
have reviewed the Release Notes and ModelForms documentation and can not
see anything that would indicate this behaviour has changed.
models.py:
{{{
from django.db import models
class Child(models.Model):
name = models.TextField()
def __unicode__(self):
return self.name
class Parent(models.Model):
name = models.TextField()
child = models.ForeignKey(Child, null=True)
def __unicode__(self):
return self.name
}}}
forms.py:
{{{
from django import forms
from .models import Parent, Child
class ParentForm(forms.ModelForm):
# field definition only set so `required = False`. Have also tried
# a custom ParentForm.__init__ with `self.fields['child'].required =
False`
child = forms.ModelChoiceField(
queryset=Child.objects.all(),
required=False
)
class Meta:
model = Parent
fields = ('name', 'child')
def __init__(self, *args, **kwargs):
super(ParentForm, self).__init__(*args, **kwargs)
# self.fields['child'].required = False
}}}
tests.py:
{{{
from django.test import TestCase
from .forms import ParentForm
from .models import Parent, Child
class ParentFormTest(TestCase):
def test_unset(self):
p = Parent.objects.create(
name='p',
child=Child.objects.create(name='c')
)
form = ParentForm(
data={'name': 'new name', 'child': None},
instance=p
)
self.assertTrue(form.is_valid())
form.save()
obj = Parent.objects.get()
self.assertEqual(obj.name, 'new name')
self.assertIsNone(obj.child) # ASSERTION FAILS
def test_set_alternative(self):
p = Parent.objects.create(
name='p',
child=Child.objects.create(name='c')
)
form = ParentForm(
data={'name': 'new name',
'child': Child.objects.create(name='alt').id},
instance=p
)
self.assertTrue(form.is_valid())
form.save()
obj = Parent.objects.get()
self.assertEqual(obj.name, 'new name')
self.assertEqual(obj.child.name, 'alt') # ASSERTION WORKS
}}}
Result when running against Django 1.8.5:
{{{
Creating test database for alias 'default'...
.F
======================================================================
FAIL: test_unset (demo.tests.ParentFormTest)
----------------------------------------------------------------------
Traceback (most recent call last):
File "/home/user/modelform-issue/demo/tests.py", line 24, in test_unset
self.assertIsNone(obj.child) # ASSERTION FAILS
AssertionError: <Child: c> is not None
----------------------------------------------------------------------
Ran 2 tests in 0.007s
FAILED (failures=1)
Destroying test database for alias 'default'...
}}}
I have tried tracing through the ModelForm.save code with pdb. The
form.cleaned_data appears correct (`{'name': u'new name', 'child': None}`.
At the point that `save_instance` is called, it appears that the
`instance.child`.
--
Ticket URL: <https://code.djangoproject.com/ticket/25349>
Django <https://code.djangoproject.com/>
The Web framework for perfectionists with deadlines.
--
You received this message because you are subscribed to the Google Groups
"Django updates" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
To post to this group, send email to [email protected].
To view this discussion on the web visit
https://groups.google.com/d/msgid/django-updates/051.c4115984633c6a9d5348efe33710983c%40djangoproject.com.
For more options, visit https://groups.google.com/d/optout.
