[QUESTION] why replace "_" with "-" in command name?

[bloodynumen]

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

from typing import Optional

import typer

app = typer.Typer()


@app.command()
def hello_test(name: Optional[str] = None):
    if name:
        typer.echo(f"Hello {name}")
    else:
        typer.echo("Hello World!")

if __name__ == "__main__":
    app()

Description

expect: python main.py hello_test --name world
actually: python main.py hello-test --name world

I found the "_" in command name is replaced with "-".
source code https://github.com/tiangolo/typer/blob/master/typer/main.py#L390

why do this?

Thank u

Operating System

macOS

Operating System Details

No response

Typer Version

0.4.0

Python Version

3.9.7

Additional Context

No response

[daddycocoaman]

This is probably just a design choice based around natural CLI convention. You're usually gonna find dashes in commands in any CLI, not underscores. If you want to keep the underscore, you can just specify the command name manually in the app.command().

[mbopfNIH]

This type of undocumented behavior is why I have decided not to use Typer. I like a lot of things about the package, but it's not worth the learning curve of digging through the code when something doesn't work as expected.

[targhs]

I guess that helps

[manueldeprada]

In fact, this is something that comes from the "click" package which typer uses as a base. If it helps, it comes from here:

https://github.com/pallets/click/blob/dc918b48fb9006be683a684b42cc7496ad649b83/src/click/core.py#L2633

[Timmmm]

Yeah this is pretty annoying. Is there any way to disable this behaviour? There doesn't seem to be anything in typer.Option(). In fact I couldn't find any reference documentation at all...?

[manueldeprada]

Yeah this is pretty annoying. Is there any way to disable this behaviour? There doesn't seem to be anything in typer.Option(). In fact I couldn't find any reference documentation at all...?

I don’t think so, since it comes from click. I switched to Python Fire by google.

[Timmmm]

Ok this comes from get_command_name().

You can fix it like this:

typer.main.get_command_name = lambda name: name

I suggest an annotation on def main() to allow you to configure whether or not this happens.

Also note for bool options you'll get --no-foo_bar which is a bit weird but whatever.

[Timmmm]

I switched to Python Fire by google.

Ah I hadn't heard of that. Had a look but it seems like it has a slightly different focus and also doesn't support type hints which is like 90% of the reason for using Typer. I'll stick with my get_command_name hack for now I reckon.

[manueldeprada]

Ok this comes from get_command_name().

You can fix it like this:

typer.main.get_command_name = lambda name: name

I suggest an annotation on def main() to allow you to configure whether or not this happens.

Also note for bool options you'll get --no-foo_bar which is a bit weird but whatever.

Hmm interesting. Can you check if it also works for option names? I mean like --cool_option gets transformed into cool-option? Thanks :)

[Timmmm]

Hmm interesting. Can you check if it also works for option names? I mean like --cool_option gets transformed into cool-option? Thanks :)

Yep that's how I'm using it.

#!/usr/bin/env python3

import typer
from typing_extensions import Annotated

typer.main.get_command_name = lambda name: name

def main(foo_bar: Annotated[int, typer.Option(help="Do a thing.")]):
    return 0

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

❯ ./test.py --help
                                                                                                             
 Usage: test.py [OPTIONS]                                                                                    
                                                                                                             
╭─ Options ─────────────────────────────────────────────────────────────────────────────────────────────────╮
│ *  --foo_bar        INTEGER  Do a thing. [default: None] [required]                                       │
│    --help                    Show this message and exit.                                                  │
╰───────────────────────────────────────────────────────────────────────────────────────────────────────────╯

[VladikaAndrii]

Хм цікаво. Чи можете ви перевірити, чи це також працює для назв параметрів? Я маю на увазі, як --cool_option перетворюється на cool-option? Дякую :)

Так, я цим користуюся.

#!/usr/bin/env python3

import typer
from typing_extensions import Annotated

typer.main.get_command_name = lambda name: name

def main(foo_bar: Annotated[int, typer.Option(help="Do a thing.")]):
    return 0

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

❯ ./test.py --help
                                                                                                             
 Usage: test.py [OPTIONS]                                                                                    
                                                                                                             
╭─ Options ─────────────────────────────────────────────────────────────────────────────────────────────────╮
│ *  --foo_bar        INTEGER  Do a thing. [default: None] [required]                                       │
│    --help                    Show this message and exit.                                                  │
╰───────────────────────────────────────────────────────────────────────────────────────────────────────────╯

Thanks, you saved me a lot of time!

[jaraco]

Personally, I prefer the dash convention because it allows for less typing. On many (most?) keyboard layouts, - is a single keystroke, whereas _ is a shifted keystroke, requiring three motions in coordination versus one.

[Timmmm]

Yeah that's an advantage for sure. I guess it's up to you whether it outweighs the disadvantage of making the code harder to follow.

Another disadvantage of using _ I've found is that for bool arguments Typer generates --no-foo_bar which is just weird!

[gajop-ptx]

There are plenty cases where this automatic replacement of "_" with "-" does more harm than good.

I am often the user of my CLI programs, and not being able to directly copy-paste (or programatically generate) use cases from the API is annoying, but most of all, this hinders search / refactoring capability.

CLI programs are, for the most part, refactored by text search & replacement, and it's annoying to think about underscore/dash in these scenarios.

This

typer.main.get_command_name = lambda name: name

can suffice for now, but a more reliable (proper API) option is necessary, as this might break at any time, since it's not part of the API.