Merge pull request #1442 from Anton-Shutik/master

RelatedField default value handling fixed

rest_framework/fields.py

@@ -301,6 +301,11 @@ class WritableField(Field):
         result.validators = self.validators[:]
         return result
 
+    def get_default_value(self):
+        if is_simple_callable(self.default):
+            return self.default()
+        return self.default
+
     def validate(self, value):
         if value in validators.EMPTY_VALUES and self.required:
             raise ValidationError(self.error_messages['required'])
@@ -349,10 +354,7 @@ class WritableField(Field):
         except KeyError:
             if self.default is not None and not self.partial:
                 # Note: partial updates shouldn't set defaults
-                if is_simple_callable(self.default):
-                    native = self.default()
-                else:
-                    native = self.default
+                native = self.get_default_value()
             else:
                 if self.required:
                     raise ValidationError(self.error_messages['required'])

rest_framework/relations.py

@@ -119,6 +119,14 @@ class RelatedField(WritableField):
 
     choices = property(_get_choices, _set_choices)
 
+    ### Default value handling
+
+    def get_default_value(self):
+        default = super(RelatedField, self).get_default_value()
+        if self.many and default is None:
+            return []
+        return default
+
     ### Regular serializer stuff...
 
     def field_to_native(self, obj, field_name):
@@ -167,7 +175,7 @@ class RelatedField(WritableField):
         except KeyError:
             if self.partial:
                 return
-            value = [] if self.many else None
+            value = self.get_default_value()
 
         if value in self.null_values:
             if self.required:

rest_framework/tests/test_serializer.py

@@ -900,6 +900,58 @@ class DefaultValueTests(TestCase):
         self.assertEqual(instance.text, 'overridden')
 
 
+class WritableFieldDefaultValueTests(TestCase):
+
+    def setUp(self):
+        self.expected = {'default': 'value'}
+        self.create_field = fields.WritableField
+
+    def test_get_default_value_with_noncallable(self):
+        field = self.create_field(default=self.expected)
+        got = field.get_default_value()
+        self.assertEqual(got, self.expected)
+
+    def test_get_default_value_with_callable(self):
+        field = self.create_field(default=lambda : self.expected)
+        got = field.get_default_value()
+        self.assertEqual(got, self.expected)
+
+    def test_get_default_value_when_not_required(self):
+        field = self.create_field(default=self.expected, required=False)
+        got = field.get_default_value()
+        self.assertEqual(got, self.expected)
+
+    def test_get_default_value_returns_None(self):
+        field = self.create_field()
+        got = field.get_default_value()
+        self.assertIsNone(got)
+
+    def test_get_default_value_returns_non_True_values(self):
+        values = [None, '', False, 0, [], (), {}] # values that assumed as 'False' in the 'if' clause
+        for expected in values:
+            field = self.create_field(default=expected)
+            got = field.get_default_value()
+            self.assertEqual(got, expected)
+
+
+class RelatedFieldDefaultValueTests(WritableFieldDefaultValueTests):
+
+    def setUp(self):
+        self.expected = {'foo': 'bar'}
+        self.create_field = relations.RelatedField
+
+    def test_get_default_value_returns_empty_list(self):
+        field = self.create_field(many=True)
+        got = field.get_default_value()
+        self.assertListEqual(got, [])
+
+    def test_get_default_value_returns_expected(self):
+        expected = [1, 2, 3]
+        field = self.create_field(many=True, default=expected)
+        got = field.get_default_value()
+        self.assertListEqual(got, expected)
+
+
 class CallableDefaultValueTests(TestCase):
     def setUp(self):
         class CallableDefaultValueSerializer(serializers.ModelSerializer):