Decorating the main function

@hydra.main can be used over decorated functions:

app.py

from omegaconf import DictConfig, OmegaConf
import hydra

from mypackage import mydecorator

@hydra.main(version_base=None)
@mydecorator
def my_app(cfg: DictConfig) -> None:
    print(OmegaConf.to_yaml(cfg))

mypackage.py

from functools import wraps
from typing import Callable

from omegaconf import DictConfig

def mydecorator(func: Callable) -> Callable:
  @wraps(func)
  def inner_decorator(cfg: DictConfig):
    print(OmegaConf.to_yaml(cfg))  # do some stuff
    return func(cfg) # pass cfg to decorated function

  return inner_decorator

Decorator should be compatible with rules below:

1. It should be created using @functools.wraps decorator
2. It should accept an argument of type omegaconf.DictConfig and pass it to the underlying function

info

@functools.wraps passes name and docstring of underlying function to the decorated one.

But more importantly, it saves underlying function into __wrapped__ attribute of decorated function, which is used by hydra.main to calculate the absolute path of config file.

Without @wraps hydra will fail while searching for the config path:

hydra.errors.MissingConfigException: Primary config directory not found.
Check that the config directory '/usr/local/lib/python3.7/conf' exists and readable