How to use the `flag_value` option properly?

[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 typer
from typer import Argument, Option


def main(
    const_option: str = Option(
        "foo",
        "--const_option",
        is_flag=True,
        flag_value="bar",
    ),
):
    print(const_option)


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

Description

What I expect:

C:\>script
foo

C:\>script --const_option
bar

What happens:

C:\>script
bar

C:\>script --const_option
bar

Not sure what I am doing wrong here, can someone point me to the right direction?

Operating System

Windows

Operating System Details

No response

Typer Version

0.4.0

Python Version

Python 3.9.4

Additional Context

No response

[alexreg]

The is_flag and flag_value parameters seem to be features of Click, not Typer. (They do not actually appear in the official Typer documentation.) This is probably an issue with Typer just blindly forwarding on these keyword arguments to Click, but it not working well with how Typer (specifically) handles default values. So, while this could be construed as a bug, the author of typer may also validly claim, "I had no intentions to explicitly support is_flag and flag_value in Typer". I don't particularly want to second-guess him, but since he seems to be very busy and is strongly encouraging other users to reply to issues, these are just my thoughts. :-)

[YuriiMotov]

These options are deprecated and shouldn't be used: #987