Fix #498 -- Reset GFK fields when content object is None (#499)

CHANGELOG.md

@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 ### Added
 
 ### Changed
+- Reset `content_type` and `object_id` fields when the content object is `None`
 
 ### Removed
 

model_bakery/baker.py

@@ -695,21 +695,27 @@ def _handle_m2m(self, instance: Model):
     def _handle_generic_foreign_keys(self, instance: Model, attrs: Dict[str, Any]):
         """Set content type and object id for GenericForeignKey fields."""
         for field_name, data in attrs.items():
-            content_type_field = data["content_type_field"]
-            object_id_field = data["object_id_field"]
+            ct_field_name = data["content_type_field"]
+            oid_field_name = data["object_id_field"]
             value = data["value"]
             if is_iterator(value):
                 value = next(value)
             if value is None:
-                continue
-
-            setattr(instance, field_name, value)
-            setattr(
-                instance,
-                content_type_field,
-                contenttypes_models.ContentType.objects.get_for_model(value),
-            )
-            setattr(instance, object_id_field, value.pk)
+                # when GFK is None, we should try to set the content type and object id to None
+                content_type_field = instance._meta.get_field(ct_field_name)
+                object_id_field = instance._meta.get_field(oid_field_name)
+                if content_type_field.null:
+                    setattr(instance, ct_field_name, None)
+                if object_id_field.null:
+                    setattr(instance, oid_field_name, None)
+            else:
+                setattr(instance, field_name, value)
+                setattr(
+                    instance,
+                    ct_field_name,
+                    contenttypes_models.ContentType.objects.get_for_model(value),
+                )
+                setattr(instance, oid_field_name, value.pk)
 
     def _remote_field(
         self, field: Union[ForeignKey, OneToOneField]

tests/generic/models.py

@@ -295,6 +295,16 @@ class DummyGenericForeignKeyModel(models.Model):
     class DummyGenericRelationModel(models.Model):
         relation = GenericRelation(DummyGenericForeignKeyModel)
 
+    class GenericForeignKeyModelWithOptionalData(models.Model):
+        content_type = models.ForeignKey(
+            contenttypes.ContentType, on_delete=models.CASCADE, blank=True, null=True
+        )
+        object_id = models.PositiveIntegerField(blank=True, null=True)
+        content_object = GenericForeignKey("content_type", "object_id")
+
+    class GenericRelationModelWithOptionalData(models.Model):
+        relation = GenericRelation(GenericForeignKeyModelWithOptionalData)
+
 
 class DummyNullFieldsModel(models.Model):
     null_foreign_key = models.ForeignKey(

tests/test_filling_fields.py

@@ -374,6 +374,16 @@ def test_with_fill_optional(self):
         assert isinstance(dummy.content_type, ContentType)
         assert dummy.content_type.model_class() is not None
 
+    def test_with_fill_optional_but_content_object_none(self):
+        dummy = baker.make(
+            models.GenericForeignKeyModelWithOptionalData,
+            content_object=None,
+            _fill_optional=True,
+        )
+        assert dummy.content_object is None
+        assert dummy.content_type is None
+        assert dummy.object_id is None
+
 
 @pytest.mark.django_db
 class TestFillingForeignKeyFieldWithDefaultFunctionReturningId: