Fix Recipe.prepare without _quantity (on one-to-one relation) (#512)

Co-authored-by: velizhanin_ie <[email protected]>

model_bakery/recipe.py

@@ -164,9 +164,11 @@ def prepare(
         **attrs: Any,
     ) -> Union[M, List[M]]:
         defaults = {
-            "_quantity": _quantity,
             "_save_related": _save_related,
         }
+        if _quantity is not None:
+            defaults["_quantity"] = _quantity  # type: ignore[assignment]
+
         defaults.update(attrs)
         return baker.prepare(
             self._model, _using=_using, **self._mapping(_using, defaults)

tests/test_baker.py

@@ -20,7 +20,9 @@
 )
 from model_bakery.timezone import tz_aware
 from tests.generic import models
+from tests.generic.baker_recipes import lonely_person
 from tests.generic.forms import DummyGenericIPAddressFieldForm
+from tests.generic import baker_recipes
 
 
 def test_import_seq_from_baker():
@@ -286,6 +288,12 @@ def test_create_one_to_one(self):
         assert lonely_person.pk is None
         assert lonely_person.only_friend.pk
 
+    def test_recipe_prepare_model_with_one_to_one_and_save_related(self):
+        lonely_person = baker_recipes.lonely_person.prepare(_save_related=True)
+
+        assert lonely_person.pk is None
+        assert lonely_person.only_friend.pk
+
 
 @pytest.mark.django_db
 class TestBakerCreatesAssociatedModels(TestCase):