Fix default values always being False for browsable API

This fixes a bug that was introduced in 28ff6fb [1] for the
browsable API, specifically with how it handled default values
for boolean fields.  Previously, it had a global default for
boolean fields set to `False`, which was different than the
standard None that was used elsewhere.  Because this only needed
to be done for the browsable API, a fix was put into place that
only set the default to `False` when form data was passed into
the serializer.  This had the unintended side effect of overriding
any default set on the boolean field.

This fixes #1101 [2] by only overriding the default if the default is
`None`, which is the default for all fields.

[1]: 28ff6fb1ec
[2]: https://github.com/tomchristie/django-rest-framework/issues/1101

rest_framework/fields.py

@@ -428,7 +428,7 @@ class BooleanField(WritableField):
     def field_from_native(self, data, files, field_name, into):
         # HTML checkboxes do not explicitly represent unchecked as `False`
         # we deal with that here...
-        if isinstance(data, QueryDict):
+        if isinstance(data, QueryDict) and self.default is None:
             self.default = False
 
         return super(BooleanField, self).field_from_native(

rest_framework/tests/test_serializer.py

@@ -1743,3 +1743,42 @@ class TestSerializerTransformMethods(TestCase):
                 'b_renamed': None,
             }
         )
+
+
+class DefaultTrueBooleanModel(models.Model):
+    cat = models.BooleanField(default=True)
+    dog = models.BooleanField(default=False)
+
+
+class SerializerDefaultTrueBoolean(TestCase):
+
+    def setUp(self):
+        super(SerializerDefaultTrueBoolean, self).setUp()
+
+        class DefaultTrueBooleanSerializer(serializers.ModelSerializer):
+            class Meta:
+                model = DefaultTrueBooleanModel
+                fields = ('cat', 'dog')
+
+        self.default_true_boolean_serializer = DefaultTrueBooleanSerializer
+
+    def test_enabled_as_false(self):
+        serializer = self.default_true_boolean_serializer(data={'cat': False,
+                                                                'dog': False})
+        self.assertEqual(serializer.is_valid(), True)
+        self.assertEqual(serializer.data['cat'], False)
+        self.assertEqual(serializer.data['dog'], False)
+
+    def test_enabled_as_true(self):
+        serializer = self.default_true_boolean_serializer(data={'cat': True,
+                                                                'dog': True})
+        self.assertEqual(serializer.is_valid(), True)
+        self.assertEqual(serializer.data['cat'], True)
+        self.assertEqual(serializer.data['dog'], True)
+
+    def test_enabled_partial(self):
+        serializer = self.default_true_boolean_serializer(data={'cat': False},
+                                                          partial=True)
+        self.assertEqual(serializer.is_valid(), True)
+        self.assertEqual(serializer.data['cat'], False)
+        self.assertEqual(serializer.data['dog'], False)