modelForm/unique_together error 'Foo bar with this None and None already exists.'

[johnsmith]

"Foo bar with this None and None already exists."

Try to save a combination of foo and bar that already exists using the form below and the
error message says "this None and None", comment out the field
overrides and there's no problem.
Not sure whether the problem is with unique_together or ModelForm.

Models

class Foo(models.Model):
    f = models.IntegerField(unique=True)
    def __unicode__(self):
        return 'Foo with f = %d' % self.f

class Bar(models.Model):
    b = models.IntegerField(unique=True)
    def __unicode__(self):
        return 'Bar with b = %d' % self.b

class FooBar(models.Model):
   foo = models.ForeignKey('Foo')
   bar = models.ForeignKey('Bar')

   class Meta:
       unique_together = (('foo','bar'),)

Form

class FooBarForm(forms.ModelForm):
    foo = forms.ModelChoiceField(Foo.objects.all()) # comment this line out an the error message is correct
    bar = forms.ModelChoiceField(Bar.objects.all()) # comment this line out an the error message is correct

    class Meta:
        model = FooBar

[Karen Tracey]

#12341 reported this problem also for the unique (not unique_together) error message, plus has some description about what is causing it. The two should be fixed at the same time, so that was closed as a dupe of this.

[Ramiro Morales]

The previous patch reduced to only contain the regression tests that demonstrate this was solved with the model-validation branch merge

[Ramiro Morales]

Current status is:

1. 12304-ensure-readable-label-in-unique-validation_error-messages.diff-- patch applicable to the 1.1.x branch to fix this issue.
2. 12304-only-tests-trunk-r12159.diff -- Patch for trunk that only adds the regression tests because there the issue was fixed with the model-validation branch merge.

[Honza Král]

(In [14198]) Fixed #12304 -- regression tests to make sure the validation messages for unique violations are sane, Thanks ramiro!