Fixed #36786 -- Fixed XML serialization of None values in natural keys.

None values in natural keys were incorrectly serialized as the string
"None", causing deserialization to fail for fields like UUIDField.

2 files changed, 94 insertions, 0 deletions

diff --git a/tests/serializers/models/natural.py b/tests/serializers/models/natural.py
index f32d781a76..3b01385e8f 100644
--- a/tests/serializers/models/natural.py
+++ b/tests/serializers/models/natural.py
@@ -91,3 +91,31 @@ class PostToOptOutSubclassUser(models.Model):
     subscribers = models.ManyToManyField(
         SubclassNaturalKeyOptOutUser, related_name="subscribed_posts", blank=True
     )
+
+
+class NaturalKeyWithNullableFieldManager(models.Manager):
+    def get_by_natural_key(self, name, optional_id):
+        return self.get(name=name, optional_id=optional_id)
+
+
+class NaturalKeyWithNullableField(models.Model):
+    name = models.CharField(max_length=100)
+    optional_id = models.CharField(max_length=100, null=True, blank=True)
+
+    objects = NaturalKeyWithNullableFieldManager()
+
+    class Meta:
+        unique_together = [["name", "optional_id"]]
+
+    def natural_key(self):
+        return (self.name, self.optional_id)
+
+
+class FKToNaturalKeyWithNullable(models.Model):
+    ref = models.ForeignKey(
+        NaturalKeyWithNullableField, on_delete=models.CASCADE, null=True
+    )
+    refs = models.ManyToManyField(
+        NaturalKeyWithNullableField, related_name="m2m_referrers"
+    )
+    data = models.CharField(max_length=100, default="")
diff --git a/tests/serializers/test_natural.py b/tests/serializers/test_natural.py
index 322abeb7fc..e5592f97c8 100644
--- a/tests/serializers/test_natural.py
+++ b/tests/serializers/test_natural.py
@@ -6,8 +6,10 @@ from .models import (
     Child,
     FKAsPKNoNaturalKey,
     FKDataNaturalKey,
+    FKToNaturalKeyWithNullable,
     NaturalKeyAnchor,
     NaturalKeyThing,
+    NaturalKeyWithNullableField,
     NaturalPKWithDefault,
     PostToOptOutSubclassUser,
     SubclassNaturalKeyOptOutUser,
@@ -280,6 +282,60 @@ def natural_key_opt_out_test(self, format):
     )
 
 
+def nullable_natural_key_fk_test(self, format):
+    target_with_none = NaturalKeyWithNullableField.objects.create(
+        name="test_none",
+        optional_id=None,
+    )
+    target_with_value = NaturalKeyWithNullableField.objects.create(
+        name="test_value",
+        optional_id="some_id",
+    )
+    fk_to_none = FKToNaturalKeyWithNullable.objects.create(
+        ref=target_with_none,
+        data="points_to_none",
+    )
+    fk_to_value = FKToNaturalKeyWithNullable.objects.create(
+        ref=target_with_value,
+        data="points_to_value",
+    )
+    objects = [target_with_none, target_with_value, fk_to_none, fk_to_value]
+    serialized = serializers.serialize(
+        format,
+        objects,
+        use_natural_foreign_keys=True,
+        use_natural_primary_keys=True,
+    )
+    objs = list(serializers.deserialize(format, serialized))
+    self.assertEqual(objs[2].object.ref_id, target_with_none.pk)
+    self.assertEqual(objs[3].object.ref_id, target_with_value.pk)
+
+
+def nullable_natural_key_m2m_test(self, format):
+    target_with_none = NaturalKeyWithNullableField.objects.create(
+        name="test_none",
+        optional_id=None,
+    )
+    target_with_value = NaturalKeyWithNullableField.objects.create(
+        name="test_value",
+        optional_id="some_id",
+    )
+    m2m_obj = FKToNaturalKeyWithNullable.objects.create(data="m2m_test")
+    m2m_obj.refs.set([target_with_none, target_with_value])
+    objects = [target_with_none, target_with_value, m2m_obj]
+    serialized = serializers.serialize(
+        format,
+        objects,
+        use_natural_foreign_keys=True,
+        use_natural_primary_keys=True,
+    )
+    objs = list(serializers.deserialize(format, serialized))
+    self.assertCountEqual(
+        objs[2].m2m_data["refs"],
+        [target_with_none.pk, target_with_value.pk],
+    )
+
+
 # Dynamically register tests for each serializer
 register_tests(
     NaturalKeySerializerTests,
@@ -319,3 +375,13 @@ register_tests(
     "test_%s_natural_key_opt_out",
     natural_key_opt_out_test,
 )
+register_tests(
+    NaturalKeySerializerTests,
+    "test_%s_nullable_natural_key_fk",
+    nullable_natural_key_fk_test,
+)
+register_tests(
+    NaturalKeySerializerTests,
+    "test_%s_nullable_natural_key_m2m",
+    nullable_natural_key_m2m_test,
+)