Created a new serializer field NullBooleanField to fix #1422. This field

is used as the default for Django's `NullBooleanField` in `ModelSerializer`s; it
differs from `BooleanField` in that it is nullable and therefore allows `None`
values.

rest_framework/fields.py

@@ -453,6 +453,26 @@ class BooleanField(WritableField):
         return bool(value)
 
 
+class NullBooleanField(WritableField):
+    type_name = 'NullBooleanField'
+    type_label = 'null boolean'
+    form_field_class = forms.NullBooleanField
+    widget = widgets.NullBooleanSelect
+    default_error_messages = {
+        'invalid': _("'%s' value must be either None, True or False."),
+    }
+    empty = None
+
+    def from_native(self, value):
+        if value is None:
+            return None
+        if value in ('true', 't', 'True', '1'):
+            return True
+        if value in ('false', 'f', 'False', '0'):
+            return False
+        return bool(value)
+
+
 class CharField(WritableField):
     type_name = 'CharField'
     type_label = 'string'

rest_framework/serializers.py

@@ -648,7 +648,7 @@ class ModelSerializer(Serializer):
         models.TextField: CharField,
         models.CommaSeparatedIntegerField: CharField,
         models.BooleanField: BooleanField,
-        models.NullBooleanField: BooleanField,
+        models.NullBooleanField: NullBooleanField,
         models.FileField: FileField,
         models.ImageField: ImageField,
     }

rest_framework/tests/test_serializer.py

@@ -1,5 +1,6 @@
 # -*- coding: utf-8 -*-
 from __future__ import unicode_literals
+from django import forms
 from django.db import models
 from django.db.models.fields import BLANK_CHOICE_DASH
 from django.test import TestCase
@@ -1847,19 +1848,12 @@ class BooleanFieldTypeTest(TestCase):
         bfield = self.serializer.get_fields()['done']
         self.assertEqual(type(bfield), fields.BooleanField)
 
-    def test_nullbooleanfield_type(self):
-        '''
-        Test that BooleanField is infered from models.NullBooleanField
-
-        https://groups.google.com/forum/#!topic/django-rest-framework/D9mXEftpuQ8
-        '''
-        bfield = self.serializer.get_fields()['started']
-        self.assertEqual(type(bfield), fields.BooleanField)
-
 
 class NullBooleanFieldModel(models.Model):
     """
-    A model for use in the NullBooleanFieldSerializer test.
+    A model for use in the NullBooleanFieldSerializer test. Showcases
+    all variations of the 'default' parameter (which is allowed to be
+    unset unlike models.BooleanField.
     """
     cat = models.NullBooleanField(default=True)
     dog = models.NullBooleanField(default=False)
@@ -1881,43 +1875,51 @@ class NullBooleanFieldSerializerTest(TestCase):
                 fields = ('cat', 'dog', 'rat')
 
         self.serializer = NullBooleanFieldSerializer
+        # For ease we save a reference to the fields we need.
+        self.fields = self.serializer.Meta.fields
 
     def test_false(self):
-        data = {
-            'cat': False,
-            'dog': False,
-            'rat': False
-        }
-        serializer = self.serializer(data=data)
-        self.assertEqual(serializer.is_valid(), True)
-        self.assertEqual(serializer.data['cat'], False)
-        self.assertEqual(serializer.data['dog'], False)
-        self.assertEqual(serializer.data['rat'], False)
+        """
+        Check that all 'falsy' inputs result in the correct output
+        to the data dictionary across all our variations of NullBooleanField.
+        """
+        falsy_values = ['false', 'f', 'False', '0', False, 0, '']
+        for val in falsy_values:
+            # For each falsy value, we create a data dictionary where all
+            # fields are set to that falsy value and then check for the
+            # desired serializer output: False.
+            data = dict([(field, val) for field in self.fields])
+            serializer = self.serializer(data=data)
+            self.assertEqual(serializer.is_valid(), True)
+            for field in self.fields:
+                self.assertEqual(serializer.data[field], False)
 
     def test_true(self):
-        data = {
-            'cat': True,
-            'dog': True,
-            'rat': True
-        }
-
-        serializer = self.serializer(data=data)
-        self.assertEqual(serializer.is_valid(), True)
-        self.assertEqual(serializer.data['cat'], True)
-        self.assertEqual(serializer.data['dog'], True)
-        self.assertEqual(serializer.data['rat'], True)
+        """
+        Check that all 'truthy' inputs result in the correct output
+        to the data dictionary across all our variations of NullBooleanField.
+        """
+        truthy_values = ['true', 't', 'True', '1', True, 1, 'truthy-string']
+        for val in truthy_values:
+            # For each truthy value, we create a data dictionary where all
+            # fields are set to that falsy value and then check for the
+            # desired serializer output: True.
+            data = dict([(field, val) for field in self.fields])
+            serializer = self.serializer(data=data)
+            self.assertEqual(serializer.is_valid(), True)
+            for field in self.fields:
+                self.assertEqual(serializer.data[field], True)
 
     def test_none(self):
-        data = {
-            'cat': None,
-            'dog': None,
-            'rat': None
-        }
+        """
+        Check that all 'None' input result in the correct output
+        to the data dictionary across all our variations of NullBooleanField.
+        """
+        data = dict([(field, None) for field in self.fields])
         serializer = self.serializer(data=data)
         self.assertEqual(serializer.is_valid(), True)
-        self.assertEqual(serializer.data['cat'], None)
-        self.assertEqual(serializer.data['dog'], None)
-        self.assertEqual(serializer.data['rat'], None)
+        for field in self.fields:
+            self.assertEqual(serializer.data[field], None)
 
     def test_partial(self):
         serializer = self.serializer(data={'rat': None}, partial=True)
@@ -1925,3 +1927,22 @@ class NullBooleanFieldSerializerTest(TestCase):
         self.assertEqual(serializer.data['cat'], True)
         self.assertEqual(serializer.data['dog'], False)
         self.assertEqual(serializer.data['rat'], None)
+
+    def test_nullbooleanfield_type(self):
+        """
+        Test that DRF's NullBooleanField is selected by default for
+        Django's NullBooleanFields.
+        """
+        serializer = self.serializer()
+        for field in self.fields:
+            bfield = serializer.get_fields()[field]
+            self.assertEqual(type(bfield), fields.NullBooleanField)
+
+    def test_nullbooleanfield_widget_type(self):
+        """
+        Test that Django's NullBooleanSelect widget is used as the default
+        widget for DRF's NullBooleanField.
+        """
+        serializer = self.serializer()
+        for field_name, field in serializer.fields.iteritems():
+            self.assertEqual(type(field.widget), forms.NullBooleanSelect)