Composition order, defaults list

[DirkKuhn]

Hi,

I noticed the following gotcha:

from typing import Optional
from hydra_zen import store, zen

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

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

def app(test: Optional[Test] = None):
    print(f'{test=}')

test_store = store(group='test')
test_store(Test, number=0)

store(app, hydra_defaults=[{'test': 'Test'}, '_self_'], name='config')

store.add_to_hydra_store()

if __name__ == '__main__':
    zen(app).hydra_main(config_name='config', config_path=None, version_base='1.3')

prints

test=None

By putting '_self_' last in the defaults list the default value test=None from app's signature is added at the end, setting test to None. This centainly did confuse me.
Should the values from the signature and the values from the config be handled differently or is this behaviour actually wanted?

If app's config is changed to

store(app, hydra_defaults=[{'test': 'Test'}, '_self_'], test=dict(number=10), name='config')

everything works as I would expect it. The output is

test=Test(number=10)

[rsokl]

That is the expected behavior when you include _self_ as the last element in hydra_defaults. You will typically want _self_ to be the first element. See: https://hydra.cc/docs/tutorials/structured_config/defaults/

If you do store(app, hydra_defaults=['_self_', {'test': 'Test'}], name='config'), running your original program prints test=Test(number=0)