Merge pull request #1348 from yprez/none-to-empty-string_2.4

Coerce None to empty string

docs/api-guide/fields.md

@@ -157,23 +157,24 @@ Corresponds to `django.db.models.fields.BooleanField`.
 ## CharField
 
 A text representation, optionally validates the text to be shorter than `max_length` and longer than `min_length`.
+If `allow_none` is `False` (default), `None` values will be converted to an empty string.
 
 Corresponds to `django.db.models.fields.CharField`
 or `django.db.models.fields.TextField`.
 
-**Signature:** `CharField(max_length=None, min_length=None)`
+**Signature:** `CharField(max_length=None, min_length=None, allow_none=False)`
 
 ## URLField
 
 Corresponds to `django.db.models.fields.URLField`.  Uses Django's `django.core.validators.URLValidator` for validation.
 
-**Signature:** `CharField(max_length=200, min_length=None)`
+**Signature:** `CharField(max_length=200, min_length=None, allow_none=False)`
 
 ## SlugField
 
 Corresponds to `django.db.models.fields.SlugField`.
 
-**Signature:** `CharField(max_length=50, min_length=None)`
+**Signature:** `CharField(max_length=50, min_length=None, allow_none=False)`
 
 ## ChoiceField
 

rest_framework/fields.py

@@ -443,8 +443,9 @@ class CharField(WritableField):
     type_label = 'string'
     form_field_class = forms.CharField
 
-    def __init__(self, max_length=None, min_length=None, *args, **kwargs):
+    def __init__(self, max_length=None, min_length=None, allow_none=False, *args, **kwargs):
         self.max_length, self.min_length = max_length, min_length
+        self.allow_none = allow_none
         super(CharField, self).__init__(*args, **kwargs)
         if min_length is not None:
             self.validators.append(validators.MinLengthValidator(min_length))
@@ -452,7 +453,9 @@ class CharField(WritableField):
             self.validators.append(validators.MaxLengthValidator(max_length))
 
     def from_native(self, value):
-        if isinstance(value, six.string_types) or value is None:
+        if value is None and not self.allow_none:
+            return ''
+        if isinstance(value, six.string_types):
             return value
         return smart_text(value)
 

rest_framework/serializers.py

@@ -804,6 +804,10 @@ class ModelSerializer(Serializer):
                 issubclass(model_field.__class__, models.PositiveSmallIntegerField):
             kwargs['min_value'] = 0
 
+        if model_field.null and \
+                issubclass(model_field.__class__, (models.CharField, models.TextField)):
+            kwargs['allow_none'] = True
+
         attribute_dict = {
             models.CharField: ['max_length'],
             models.CommaSeparatedIntegerField: ['max_length'],

rest_framework/tests/test_serializer.py

@@ -1124,6 +1124,20 @@ class BlankFieldTests(TestCase):
         serializer = self.model_serializer_class(data={})
         self.assertEqual(serializer.is_valid(), True)
 
+    def test_create_model_null_field_save(self):
+        """
+        Regression test for #1330.
+
+        https://github.com/tomchristie/django-rest-framework/pull/1330
+        """
+        serializer = self.model_serializer_class(data={'title': None})
+        self.assertEqual(serializer.is_valid(), True)
+
+        try:
+            serializer.save()
+        except Exception:
+            self.fail('Exception raised on save() after validation passes')
+
 
 #test for issue #460
 class SerializerPickleTests(TestCase):
@@ -1490,6 +1504,7 @@ class AttributeMappingOnAutogeneratedFieldsTests(TestCase):
             image_field = models.ImageField(max_length=1024, blank=True)
             slug_field = models.SlugField(max_length=1024, blank=True)
             url_field = models.URLField(max_length=1024, blank=True)
+            nullable_char_field = models.CharField(max_length=1024, blank=True, null=True)
 
         class AMOAFSerializer(serializers.ModelSerializer):
             class Meta:
@@ -1522,6 +1537,10 @@ class AttributeMappingOnAutogeneratedFieldsTests(TestCase):
             'url_field': [
                 ('max_length', 1024),
             ],
+            'nullable_char_field': [
+                ('max_length', 1024),
+                ('allow_none', True),
+            ],
         }
 
     def field_test(self, field):
@@ -1558,6 +1577,9 @@ class AttributeMappingOnAutogeneratedFieldsTests(TestCase):
     def test_url_field(self):
         self.field_test('url_field')
 
+    def test_nullable_char_field(self):
+        self.field_test('nullable_char_field')
+
 
 class DefaultValuesOnAutogeneratedFieldsTests(TestCase):