Feature Switches in Typer

[archiif]

First Check

• I added a very descriptive title to this issue.
• I used the GitHub search to find a similar issue and didn't find it.
• I searched the Typer documentation, with the integrated search.
• I already searched in Google "How to X in Typer" and didn't find any information.
• I already read and followed all the tutorial in the docs and didn't find an answer.
• I already checked if it is not related to Typer but to Click.

Commit to Help

• I commit to help with one of those options 👆

Example Code

import sys
import click

@click.command()
@click.option('--upper', 'transformation', flag_value='upper',
              default=True)
@click.option('--lower', 'transformation', flag_value='lower')
def info(transformation):
    click.echo(getattr(sys.platform, transformation)())

Description

Is it possible to have multiple options map to a single parameter?
It's one of the basic patterns possible in Click, called Feature Switches: https://click.palletsprojects.com/en/8.0.x/options/#feature-switches
Given Typer's 1-to-1 option-to-parameter mapping, would this feature be impossible to implement in Typer? If not, what would the equivalent Typer code for the Click code above look like?

Operating System

Windows

Operating System Details

No response

Typer Version

0.4.0

Python Version

Python 3.10.0

Additional Context

No response

[YuriiMotov]

There is no such feature in Typer, but if you really need such behavior I think you can achieve this using callback and global state object:

from dataclasses import dataclass
from typing import Optional

import typer
from typing_extensions import Annotated

@dataclass
class State:
    feature_switch: str = "undefined"

state = State()

def feature_switch_callback(ctx: typer.Context, param: typer.CallbackParam, value: bool):
    if value:
        # You can add logic to make these flags mutually exclusive
        state.feature_switch = param.name
    return value

def main(
    upper: Annotated[Optional[bool], typer.Option("--upper", callback=feature_switch_callback)] = None,
    lower: Annotated[Optional[bool], typer.Option("--lower", callback=feature_switch_callback)] = None
):
    typer.echo(state.feature_switch)

if __name__ == "__main__":
    typer.run(main)

Try it:

$ python main.py --upper
upper

$ python main.py --lower
lower

$ python main.py --lower --upper
upper

$ python main.py
undefined