How to specify the value None in a config group

[DirkKuhn]

Consider the following example where the parameter item of the class Test can either be an instance of Item or None.

from typing import Optional
from omegaconf import DictConfig
from hydra_zen import to_yaml, store, builds, launch, zen, make_config

class Item:
    def __init__(self, number: int):
        self.number = number

    def __repr__(self) -> str:
        return f'Item(number={self.number})'

class Test:
    def __init__(self, item: Optional[Item] = None):
        self.item = item

    def __repr__(self) -> str:
        return f'Test(item={self.item})'

def app(zen_cfg: DictConfig, test: Test) -> None:
    print(test, end='\n\n')
    print(to_yaml(zen_cfg, resolve=True))


Config = builds(
    app,
    populate_full_signature=True,
    hydra_defaults=[
        '_self_',
        {'test': 'default'},
        {'test/item': 'none'}
    ]
)

test_store = store(group='test')
test_store(Test, name='default')

item_store = store(group='test/item')
item_store(None, name='none')

if __name__ == '__main__':
    store.add_to_hydra_store()
    launch(Config, zen(app), version_base='1.3')

I would like to create a config group in the package 'test/item' which sets the item to None. Unfortunately, the line item_store(None, name='none') doesn't set anything. Relocating in the global package seems to work, i.e.

item_store(make_config(hydra_defaults=['_self_'], test=dict(item=None), bases=(Config,)), name='none', package='_global_')

For some reason hydra_defaults=['_self_'] is necessary in make_config.
I don't like the inheritance from Config. I fear that might lead to problems if I inherit and override Config somewhere else.
Is there a better way to do this?

Thanks a lot!

[DirkKuhn]

Could something like this work?

from hydra_zen import builds, instantiate
cfg = builds(type(None))
n = instantiate(cfg)

Right now instantiate throws the error ModuleNotFoundError: No module named 'builtins.NoneType'; 'builtins' is not a package but maybe with a hard-coded import?

[jgbos]

I think you want:

from hydra_zen import instantiate, just
cfg = {"val": just(None)}
n = instantiate(cfg)
assert n["val"] is None
print(n)