Schema Validation Example

This simple example uses a --config option to load a configuration from a YAML file and uses schema to validate the file before continuing.

An example typer app:

simple_app.py

from typing import Any
from typing_extensions import Annotated

from schema import Schema
import typer
from typer_config import yaml_loader, conf_callback_factory, use_config

schema = Schema({"name": str, "greeting": str, "suffix": str})


def validator_loader(param_value: str) -> dict[str, Any]:
    conf = yaml_loader(param_value)
    conf = schema.validate(conf)  # raises an exception if not valid
    return conf


validator_callback = conf_callback_factory(validator_loader)

app = typer.Typer()


@app.command()
@use_config(validator_callback)
def main(
    name: str,
    greeting: Annotated[str, typer.Option()],
    suffix: Annotated[str, typer.Option()] = "!",
):
    typer.echo(f"{greeting}, {name}{suffix}")


if __name__ == "__main__":
    app()

With a config file:

config.yml

name: World
greeting: Hello
suffix: "!"

And invoked with python:

Terminal

$ python simple_app.py --config config.yml
Hello, World!

$ python simple_app.py --config config.yml Alice
Hello, Alice!

$ python simple_app.py --config config.yml --greeting Hi
Hi, World!