CLI Tools (tyro)

https://github.com/brentyi/tyro

tyro generates command-line interfaces directly from type hints. Because iron-monk uses standard dataclasses without heavy metaclasses, they pair flawlessly: tyro parses the inputs, and iron-monk enforces the business rules.

import sys
import tyro
import pathlib
from typing import Annotated

from monk import monk, validate
from monk.constraints import NonNegative, OneOf, Each, Len, IsDir
from monk.exceptions import ValidationError

@monk
class CLIArgs:
    target_dir: Annotated[pathlib.Path, IsDir]
    tags: Annotated[list[str], Each(Len(min_len=3))]
    max_warnings: Annotated[int, NonNegative] = 10
    output_format: Annotated[str, OneOf(["json", "text", "html"])] = "text"

def main():
    # 1. tyro parses sys.argv and builds the dataclass
    args = tyro.cli(CLIArgs)

    # 2. iron-monk validates the logic
    try:
        valid_args = validate(args)
    except ValidationError as e:
        print("❌ Invalid arguments provided:\n", file=sys.stderr)
        for err in e.errors:
            print(f"  --{err['field'].replace('_', '-')}: {err['message']}", file=sys.stderr)
        sys.exit(1)

    print(f"✅ Linting target: {valid_args.target_dir}")

if __name__ == "__main__":
    main()

Output

$ python cli_tyro.py --target-dir not-a-path --max-warnings -1 --tags john kelly smith bo --output-format yml

❌ Invalid arguments provided:

  --target-dir: Must be an existing directory.
  --tags[3]: Must have a minimum length of 3.
  --max-warnings: Must be greater than or equal to 0.
  --output-format: Must be one of: ['json', 'text', 'html'], got 'yml'.