Injection of read-only default values is done too late

rest_framework/serializers.py

@@ -431,10 +431,11 @@ def run_validation(self, data=empty):
         if is_empty_value:
             return data
 
-        value = self.to_internal_value(data)
+        value = self._to_primitive_value(data)
         try:
             self.run_validators(value)
             value = self.validate(value)
+            value = self.to_internal_value(value)
             assert value is not None, '.validate() should return the validated data'
         except (ValidationError, DjangoValidationError) as exc:
             raise ValidationError(detail=as_serializer_error(exc))
@@ -465,7 +466,7 @@ def run_validators(self, value):
         to_validate.update(value)
         super(Serializer, self).run_validators(to_validate)
 
-    def to_internal_value(self, data):
+    def _to_primitive_value(self, data):
         """
         Dict of native values <- Dict of primitive datatypes.
         """
@@ -502,6 +503,12 @@ def to_internal_value(self, data):
 
         return ret
 
+    def to_internal_value(self, data):
+        """
+        Converts a dict of primitive datatypes into the internal format
+        """
+        return data
+
     def to_representation(self, instance):
         """
         Object instance -> Dict of primitive datatypes.

tests/test_serializer.py

@@ -613,3 +613,32 @@ class Grandchild(Child):
         assert len(Parent().get_fields()) == 2
         assert len(Child().get_fields()) == 2
         assert len(Grandchild().get_fields()) == 2
+
+
+class Test5922Regression:
+    class Point(object):
+        def __init__(self, srid, x, y):
+            self.srid = srid
+            self.coords = (x, y)
+
+    def setup(self):
+
+        # Declares a serializer that converts data into an object
+        class NestedPointSerializer(serializers.Serializer):
+            longitude = serializers.FloatField(source='x')
+            latitude = serializers.FloatField(source='y')
+
+            def to_internal_value(self, data):
+                kwargs = super(NestedPointSerializer, self).to_internal_value(data)
+                return Test5922Regression.Point(srid=4326, **kwargs)
+
+        self.Serializer = NestedPointSerializer
+
+    def test_5922_regression(self):
+        serializer = self.Serializer(data={'longitude': 6.958307, 'latitude': 50.941357})
+        assert serializer.is_valid()
+        assert isinstance(serializer.validated_data, Test5922Regression.Point)
+        assert serializer.validated_data.srid == 4326
+        assert serializer.validated_data.coords[0] == 6.958307
+        assert serializer.validated_data.coords[1] == 50.941357
+        assert serializer.errors == {}