Fixed #27039 -- Fixed empty data fallback to model field default in m…

…odel forms.

django/forms/models.py

@@ -52,6 +52,11 @@ def construct_instance(form, instance, fields=None, exclude=None):
            continue
        if exclude and f.name in exclude:
            continue
        # Leave defaults for fields that aren't in POST data, except for
        # checkbox inputs because they don't appear in POST data if not checked.
        if (f.has_default() and f.name not in form.data and
                not getattr(form[f.name].field.widget, 'dont_use_model_field_default_for_empty_data', False)):
            continue
        # Defer saving file-type fields until after the other fields, so a
        # callable upload_to can use the values from other fields.
        if isinstance(f, models.FileField):

django/forms/widgets.py

@@ -481,6 +481,10 @@ def boolean_check(v):


class CheckboxInput(Widget):
    # Don't use model field defaults for fields that aren't in POST data,
    # because checkboxes don't appear in POST data if not checked.
    dont_use_model_field_default_for_empty_data = True

    def __init__(self, attrs=None, check_test=None):
        super(CheckboxInput, self).__init__(attrs)
        # check_test is a callable that takes a value and returns True

docs/releases/1.10.1.txt

@@ -79,3 +79,6 @@ Bugfixes

* Reallowed subclassing ``UserCreationForm`` without ``USERNAME_FIELD`` in
  ``Meta.fields`` (:ticket:`27111`).

* Fixed a regression in model forms where model fields with a ``default`` that
  didn't appear in POST data no longer used the ``default`` (:ticket:`27039`).

docs/topics/forms/modelforms.txt

@@ -332,6 +332,21 @@ Note that if the form :ref:`hasn't been validated
``form.errors``. A ``ValueError`` will be raised if the data in the form
doesn't validate -- i.e., if ``form.errors`` evaluates to ``True``.

If an optional field doesn't appear in the form's data, the resulting model
instance uses the model field :attr:`~django.db.models.Field.default`, if
there is one, for that field. This behavior doesn't apply to fields that use
:class:`~django.forms.CheckboxInput` (or any custom widget with
``dont_use_model_field_default_for_empty_data=True``) since an unchecked
checkbox doesn't appear in the data of an HTML form submission. Use a custom
form field or widget if you're designing an API and want the default fallback
for a ``BooleanField``.

.. versionchanged:: 1.10.1

    Older versions don't have the exception for
    :class:`~django.forms.CheckboxInput` which means that unchecked checkboxes
    receive a value of ``True`` if that's the model field default.

This ``save()`` method accepts an optional ``commit`` keyword argument, which
accepts either ``True`` or ``False``. If you call ``save()`` with
``commit=False``, then it will return an object that hasn't yet been saved to

tests/model_forms/models.py

@@ -122,6 +122,7 @@ class PublicationDefaults(models.Model):
    date_published = models.DateField(default=datetime.date.today)
    mode = models.CharField(max_length=2, choices=MODE_CHOICES, default=default_mode)
    category = models.IntegerField(choices=CATEGORY_CHOICES, default=default_category)
    active = models.BooleanField(default=True)


class Author(models.Model):

tests/model_forms/tests.py

@@ -565,6 +565,42 @@ class Meta:
        self.assertEqual(list(OrderFields2.base_fields),
                         ['slug', 'name'])

    def test_default_populated_on_optional_field(self):
        class PubForm(forms.ModelForm):
            mode = forms.CharField(max_length=255, required=False)

            class Meta:
                model = PublicationDefaults
                fields = ('mode',)

        # Empty data uses the model field default.
        mf1 = PubForm({})
        self.assertEqual(mf1.errors, {})
        m1 = mf1.save(commit=False)
        self.assertEqual(m1.mode, 'di')
        self.assertEqual(m1._meta.get_field('mode').get_default(), 'di')

        # Blank data doesn't use the model field default.
        mf2 = PubForm({'mode': ''})
        self.assertEqual(mf2.errors, {})
        m2 = mf2.save(commit=False)
        self.assertEqual(m2.mode, '')

    def test_default_not_populated_on_optional_checkbox_input(self):
        class PubForm(forms.ModelForm):
            class Meta:
                model = PublicationDefaults
                fields = ('active',)

        # Empty data doesn't use the model default because CheckboxInput
        # doesn't have a value in HTML form submission.
        mf1 = PubForm({})
        self.assertEqual(mf1.errors, {})
        m1 = mf1.save(commit=False)
        self.assertIs(m1.active, False)
        self.assertIsInstance(mf1.fields['active'].widget, forms.CheckboxInput)
        self.assertIs(m1._meta.get_field('active').get_default(), True)


class FieldOverridesByFormMetaForm(forms.ModelForm):
    class Meta:
@@ -774,7 +810,10 @@ def test_abstract_inherited_unique(self):
        title = 'Boss'
        isbn = '12345'
        DerivedBook.objects.create(title=title, author=self.writer, isbn=isbn)
        form = DerivedBookForm({'title': 'Other', 'author': self.writer.pk, 'isbn': isbn})
        form = DerivedBookForm({
            'title': 'Other', 'author': self.writer.pk, 'isbn': isbn,
            'suffix1': '1', 'suffix2': '2',
        })
        self.assertFalse(form.is_valid())
        self.assertEqual(len(form.errors), 1)
        self.assertEqual(form.errors['isbn'], ['Derived book with this Isbn already exists.'])
@@ -2491,7 +2530,7 @@ def test_callable_field_default(self):
        class PublicationDefaultsForm(forms.ModelForm):
            class Meta:
                model = PublicationDefaults
                fields = '__all__'
                fields = ('title', 'date_published', 'mode', 'category')

        self.maxDiff = 2000
        form = PublicationDefaultsForm()