Another fix idea: use default unless given custom argument

model_bakery/baker.py

@@ -351,19 +351,22 @@ def _make(
                     self.m2m_dict[field.name] = self.model_attrs.pop(field.name)
 
             elif field.name not in self.model_attrs:
+                # TODO: this might be a code going into a wrong direction, drop it if
+                #  things in `model_bakery.baker.Baker.generate_value` will work out
+                # if (
+                #     isinstance(field, ForeignKey)
+                #     and "{0}_id".format(field.name) not in self.model_attrs
+                # ):
+                #     value = self.generate_value(field, commit_related)
+                #     if isinstance(value, field.related_model):
+                #         field_name = field.name
+                #     else:
+                #         field_name = "{0}_id".format(field.name)
+                #
+                #     self.model_attrs[field_name] = value
+                #
+                # elif (
                 if (
-                    isinstance(field, ForeignKey)
-                    and "{0}_id".format(field.name) not in self.model_attrs
-                ):
-                    value = self.generate_value(field, commit_related)
-                    if isinstance(value, field.related_model):
-                        field_name = field.name
-                    else:
-                        field_name = "{0}_id".format(field.name)
-
-                    self.model_attrs[field_name] = value
-
-                elif (
                     not isinstance(field, ForeignKey)
                     or "{0}_id".format(field.name) not in self.model_attrs
                 ):
@@ -556,8 +559,8 @@ def generate_value(self, field: Field, commit: bool = True) -> Any:
         is_content_type_fk = isinstance(field, ForeignKey) and issubclass(
             self._remote_field(field).model, contenttypes.models.ContentType
         )
-
-        if field.has_default():
+        # when a default provided, we only use it unless the field is listed in `self.rel_fields`
+        if field.has_default() and field.name not in self.rel_fields:
             if callable(field.default):
                 return field.default()
             return field.default

tests/generic/models.py

@@ -271,6 +271,15 @@ class DummyForeignKeyWithDefaultIdModel(models.Model):
     )
 
 
+class DummyOptionalForeignKey(models.Model):
+    named_thing = models.ForeignKey(
+        "NamedThing",
+        null=True,
+        default=None,
+        on_delete=models.SET_NULL,
+    )
+
+
 class DummyNullFieldsModel(models.Model):
     null_foreign_key = models.ForeignKey(
         "DummyBlankFieldsModel", null=True, on_delete=models.CASCADE

tests/test_filling_fields.py

@@ -279,10 +279,24 @@ def test_filling_content_type_field(self):
 @pytest.mark.django_db
 class TestFillingForeignKeyFieldWithDefaultFunctionReturningId:
     def test_filling_foreignkey_with_default_id(self):
+        dummy = baker.make(models.DummyForeignKeyWithDefaultIdModel)
+        assert dummy.named_thing.id == models.get_default_namedthing_id()
+        assert dummy.named_thing.name == "Default"
+
+    def test_filling_foreignkey_with_default_id_with_custom_arguments(self):
         dummy = baker.make(
-            models.DummyForeignKeyWithDefaultIdModel, named_thing__name="Default"
+            models.DummyForeignKeyWithDefaultIdModel, named_thing__name="Not default"
         )
-        assert dummy.named_thing.id == models.get_default_namedthing_id()
+        assert dummy.named_thing.__class__.objects.count() == 1
+        assert dummy.named_thing.id == 1
+        assert dummy.named_thing.name == "Not default"
+
+
+@pytest.mark.django_db
+class TestFillingOptionalForeignKeyField:
+    def test_filling_optional_foreignkey_implicitly(self):
+        dummy = baker.make(models.DummyOptionalForeignKey, named_thing__name="Optional")
+        assert dummy.named_thing.name == "Optional"
 
 
 @pytest.mark.django_db