Default value will now be used when serializing if key or attribute is missing.

rest_framework/fields.py

@@ -442,7 +442,9 @@ class Field(object):
         try:
             return get_attribute(instance, self.source_attrs)
         except (KeyError, AttributeError) as exc:
-            if not self.required and self.default is empty:
+            if self.default is not empty:
+                return self.default
+            if not self.required:
                 raise SkipField()
             msg = (
                 'Got {exc_type} when attempting to get a value for field '

tests/test_serializer.py

@@ -313,6 +313,7 @@ class TestNotRequiredOutput:
         serializer.save()
         assert serializer.data == {'included': 'abc'}
 
+    @pytest.mark.skipif(True, reason='Disabling pending removal')
     def test_default_required_output_for_dict(self):
         """
         'default="something"' should require dictionary key.
@@ -328,6 +329,7 @@ class TestNotRequiredOutput:
         with pytest.raises(KeyError):
             serializer.data
 
+    @pytest.mark.skipif(True, reason='Disabling pending removal')
     def test_default_required_output_for_object(self):
         """
         'default="something"' should require object attribute.
@@ -345,6 +347,44 @@ class TestNotRequiredOutput:
             serializer.data
 
 
+class TestDefaultOutput:
+    def setup(self):
+        class ExampleSerializer(serializers.Serializer):
+            has_default = serializers.CharField(default='abc')
+            no_default = serializers.CharField()
+        self.Serializer = ExampleSerializer
+
+    def test_default_used_for_dict(self):
+        """
+        'default="something"' should be used if dictionary key is missing from input.
+        """
+        serializer = self.Serializer({'no_default': 'def'})
+        assert serializer.data == {'has_default': 'abc', 'no_default': 'def'}
+
+    def test_default_used_for_object(self):
+        """
+        'default="something"' should be used if object attribute is missing from input.
+        """
+        instance = MockObject(no_default='def')
+        serializer = self.Serializer(instance)
+        assert serializer.data == {'has_default': 'abc', 'no_default': 'def'}
+
+    def test_default_not_used_when_in_dict(self):
+        """
+        'default="something"' should not be used if dictionary key is present in input.
+        """
+        serializer = self.Serializer({'has_default': 'ghi', 'no_default': 'def'})
+        assert serializer.data == {'has_default': 'ghi', 'no_default': 'def'}
+
+    def test_default_not_used_when_in_object(self):
+        """
+        'default="something"' should not be used if object attribute is present in input.
+        """
+        instance = MockObject(has_default='ghi', no_default='def')
+        serializer = self.Serializer(instance)
+        assert serializer.data == {'has_default': 'ghi', 'no_default': 'def'}
+
+
 class TestCacheSerializerData:
     def test_cache_serializer_data(self):
         """