@override_settings for STORAGES has no effect

Using Django Mystery Errors
1

Hi,

I have followed the documentation here to have a storage backend defined in STORAGES setting:

STORAGES = {
    # Default storage that are required by django
    "default": {
        "BACKEND": "django.core.files.storage.FileSystemStorage",
    },
    "staticfiles": {
        "BACKEND": "django.contrib.staticfiles.storage.StaticFilesStorage",
    },
    # Our specific storages
    "custom": {
        "BACKEND": "path.to.MyCustomStorage",
    },
}

The documentation also indicate that to allow @override_settings STORAGES during tests, the backend must be resolved using a LazyObject in model field so it is not resolved during django’s start process:

class BlopStorage(LazyObject):
    def _setup(self):
        self._wrapped = storages["custom"]


blop_storage = BlopStorage()

class MyModel(models.Model):
    blop_file = models.FileField(
        storage=blop_storage,
        ...
    )

But it seems the storage is still resolved at boot time. I’ve debugged here and it seems the function is triggered in FileField.__init__ on self.storage = storage or default_storage line.

So later when tests ran, overriding STORAGES settings doesn’t change the model field storage.

Did I miss something ?
Is the documentation suggestion doesn’t works ?
Any idea how to make it works or allow overriding STORAGES settings ?

EDIT:
After more tests, I confirm that self.storage = storage or default_storage is triggering __bool__ on
LazyObject which force resolving the backend.
A workaround would be to add dumb __bool__ to the LazyObject.

    def __bool__(self) -> bool:
        return True

But the best fix would maybe to change how django check storage by :

self.storage = storage if storage is not None else default_storage

Thanks