Fixed #35729 -- Enabled natural key serialization opt-out for subclasses.

Refactored serialization logic to allow models inheriting a natural_key()
method (e.g. AbstractBaseUser) to explicitly opt out of natural key
serialization by returning an empty tuple from the method.

Thanks Jonas Dittrich for the report.

Co-authored-by: Jacob Walls <jacobtylerwalls@gmail.com>

1 files changed, 10 insertions, 11 deletions

diff --git a/django/core/serializers/python.py b/django/core/serializers/python.py
index 2929874b01..53a73e19e5 100644
--- a/django/core/serializers/python.py
+++ b/django/core/serializers/python.py
@@ -34,7 +34,7 @@ class Serializer(base.Serializer):
 
     def get_dump_object(self, obj):
         data = {"model": str(obj._meta)}
-        if not self.use_natural_primary_keys or not hasattr(obj, "natural_key"):
+        if not self.use_natural_primary_keys or not self._resolve_natural_key(obj):
             data["pk"] = self._value_from_field(obj, obj._meta.pk)
         data["fields"] = self._current
         return data
@@ -52,26 +52,25 @@ class Serializer(base.Serializer):
         self._current[field.name] = self._value_from_field(obj, field)
 
     def handle_fk_field(self, obj, field):
-        if self.use_natural_foreign_keys and hasattr(
-            field.remote_field.model, "natural_key"
+        if self.use_natural_foreign_keys and (
+            natural_key_value := self._resolve_fk_natural_key(obj, field)
         ):
-            related = getattr(obj, field.name)
-            if related:
-                value = related.natural_key()
-            else:
-                value = None
+            value = natural_key_value
         else:
             value = self._value_from_field(obj, field)
         self._current[field.name] = value
 
     def handle_m2m_field(self, obj, field):
         if field.remote_field.through._meta.auto_created:
-            if self.use_natural_foreign_keys and hasattr(
-                field.remote_field.model, "natural_key"
+            if self.use_natural_foreign_keys and self._model_supports_natural_key(
+                field.remote_field.model
             ):
 
                 def m2m_value(value):
-                    return value.natural_key()
+                    if natural := value.natural_key():
+                        return natural
+                    else:
+                        return self._value_from_field(value, value._meta.pk)
 
                 def queryset_iterator(obj, field):
                     attr = getattr(obj, field.name)