Added value_to_native and value_from_native methods to serializer to fix #1205.

rest_framework/relations.py

@@ -144,13 +144,17 @@ class RelatedField(WritableField):
             return None
 
         if self.many:
-            if is_simple_callable(getattr(value, 'all', None)):
-                return [self.to_native(item) for item in value.all()]
-            else:
-                # Also support non-queryset iterables.
-                # This allows us to also support plain lists of related items.
-                return [self.to_native(item) for item in value]
-        return self.to_native(value)
+            return self.value_to_native(value)
+        else:
+            return self.to_native(value)
+
+    def value_to_native(self, value):
+        if is_simple_callable(getattr(value, 'all', None)):
+            return [self.to_native(item) for item in value.all()]
+        else:
+            # Also support non-queryset iterables.
+            # This allows us to also support plain lists of related items.
+            return [self.to_native(item) for item in value]
 
     def field_from_native(self, data, files, field_name, into):
         if self.read_only:
@@ -249,12 +253,7 @@ class PrimaryKeyRelatedField(RelatedField):
                     queryset = get_component(queryset, component)
 
             # Forward relationship
-            if is_simple_callable(getattr(queryset, 'all', None)):
-                return [self.to_native(item.pk) for item in queryset.all()]
-            else:
-                # Also support non-queryset iterables.
-                # This allows us to also support plain lists of related items.
-                return [self.to_native(item.pk) for item in queryset]
+            return self.value_to_native(queryset)
 
         # To-one relationship
         try:
@@ -270,6 +269,14 @@ class PrimaryKeyRelatedField(RelatedField):
         # Forward relationship
         return self.to_native(pk)
 
+    def value_to_native(self, value):
+        if is_simple_callable(getattr(value, 'all', None)):
+            return [self.to_native(item.pk) for item in value.all()]
+        else:
+            # Also support non-queryset iterables.
+            # This allows us to also support plain lists of related items.
+            return [self.to_native(item.pk) for item in value]
+
 
 ### Slug relationships
 

rest_framework/serializers.py

@@ -351,6 +351,12 @@ class BaseSerializer(WritableField):
             field.label = pretty_name(key)
         return field
 
+    def value_from_native(self, value):
+        return value
+
+    def value_to_native(self, value):
+        return value
+
     def field_to_native(self, obj, field_name):
         """
         Override default so that the serializer can be used as a nested field
@@ -371,8 +377,9 @@ class BaseSerializer(WritableField):
         except ObjectDoesNotExist:
             return None
 
-        if is_simple_callable(getattr(value, 'all', None)):
-            return [self.to_native(item) for item in value.all()]
+        native_value = self.value_to_native(value)
+        if native_value is not None:
+            return native_value
 
         if value is None:
             return None
@@ -407,7 +414,7 @@ class BaseSerializer(WritableField):
 
         # Set the serializer object if it exists
         obj = get_component(self.parent.object, self.source or field_name) if self.parent.object else None
-        obj = obj.all() if is_simple_callable(getattr(obj, 'all', None)) else obj
+        obj = self.value_from_native(obj)
 
         if self.source == '*':
             if value:
@@ -905,6 +912,16 @@ class ModelSerializer(Serializer):
 
         return instance
 
+    def value_from_native(self, value):
+        if is_simple_callable(getattr(value, 'all', None)):
+            return value.all()
+        else:
+            return value
+
+    def value_to_native(self, value):
+        if is_simple_callable(getattr(value, 'all', None)):
+            return [self.to_native(item) for item in value.all()]
+
     def from_native(self, data, files):
         """
         Override the default method to also include model field validation.