Using Typer and Hydra together

I have a simple Typer application:

import typer

app = typer.Typer()

@app.command()
def say_hi():
    print("Hi")

@app.callback()
def main():
    pass

if __name__ == "__main__":
    app()

I would like to use Hydra for the configuration management of the app, however I am not sure how to do that without losing the ability to override the config from the CLI.

My first attempt was:

import hydra
import typer
from omegaconf import DictConfig, OmegaConf

app = typer.Typer()

@app.command()
def say_hi():
    print("Hi")

@app.callback()
@hydra.main(config_path="conf", config_name="config")
def main(cfg: DictConfig) -> None:
    print(OmegaConf.to_yaml(cfg))

if __name__ == "__main__":
    app()

But I get an error saying:

RuntimeError: Type not yet supported: <class 'omegaconf.dictconfig.DictConfig'>

If I remove the DictConfig type annotation I get an error that cfg is missing.

I saw in Hydra docs the Compose API that allows to initialize the config without decorators:

@app.callback()
def main() -> None:
    with initialize(config_path="conf", job_name="test_app"):
        cfg = compose(config_name="config")
        print(OmegaConf.to_yaml(cfg))

but It seems that I can't override config from the command line in this case as those values are not recognized by the Typer app.

Any recommendations how it can be resolved?

The compose function accepts an optional list of override strings:

with initialize(config_path="conf", job_name="test_app"):
    cfg = compose(config_name="config", overrides=["db=mysql", "db.user=me"])

You will need to get a list of override strings from the command line, then pass that list to compose. Here is an example using Typer; similar patterns could work for e.g. argparse or click. (Disclaimer: I am not a Typer expert)

from typing import List, Optional

import typer
from omegaconf import OmegaConf, DictConfig

from hydra import compose, initialize

app = typer.Typer()

def my_compose(overrides: Optional[List[str]]) -> DictConfig:
    with initialize(config_path="conf", job_name="test_app"):
        return compose(config_name="config", overrides=overrides)

@app.command()
def say_hi(overrides: Optional[List[str]] = typer.Argument(None)):
    print("HI!")
    print(f"Got {overrides=}")
    cfg = my_compose(overrides)
    print("\nHydra config:")
    print(OmegaConf.to_yaml(cfg))

@app.command()
def say_bye(overrides: Optional[List[str]] = typer.Argument(None)):
    cfg = my_compose(overrides)
    ...
    print("BYE!")

if __name__ == "__main__":
    app()

$ python my_app.py say-hi +foo=bar +baz=qux
HI!
Got overrides=('+foo=bar', '+baz=qux')

Hydra config:
foo: bar
baz: qux

$ python my_app.py say-bye
BYE!