Tweaks to display nested data in empty serializers

rest_framework/relations.py

@@ -134,9 +134,9 @@ class RelatedField(WritableField):
             value = obj
 
             for component in source.split('.'):
-                value = get_component(value, component)
                 if value is None:
                     break
+                value = get_component(value, component)
         except ObjectDoesNotExist:
             return None
 
@@ -567,8 +567,13 @@ class HyperlinkedIdentityField(Field):
         May raise a `NoReverseMatch` if the `view_name` and `lookup_field`
         attributes are not configured to correctly match the URL conf.
         """
-        lookup_field = getattr(obj, self.lookup_field)
+        lookup_field = getattr(obj, self.lookup_field, None)
         kwargs = {self.lookup_field: lookup_field}
+
+        # Handle unsaved object case
+        if lookup_field is None:
+            return None
+
         try:
             return reverse(view_name, kwargs=kwargs, request=request, format=format)
         except NoReverseMatch:

rest_framework/serializers.py

@@ -338,9 +338,9 @@ class BaseSerializer(WritableField):
             value = obj
 
             for component in source.split('.'):
-                value = get_component(value, component)
                 if value is None:
-                    break
+                    return self.to_native(None)
+                value = get_component(value, component)
         except ObjectDoesNotExist:
             return None