"-c never" and NO_COLOR are not respected for -h and other usage messages

[arp242]

When adding -c never I would expect it to also apply to the -h output, but that's still coloured:

This also applies to something like fd -c none -v, which is an error but has coloured (hard to read) output:

In general, I'd really recommend to be careful with coloured terminal stuff, because what's helpful for one personal might be next-to-unreadable for the next (especially if it's non-configurable).

This is fd 8.1.0 on Void Linux.

[sharkdp]

Thank you for reporting this. That should be fixed, if possible (I'm not entirely sure if clap allows us to read the value of --color=… when using -h, but I would hope so). Things could certainly be changed for NO_COLOR.

[tpiekarski]

@sharkdp If you did not yet take a look, I'd like to try to debug and offer a PR

[sharkdp]

@sharkdp If you did not yet take a look, I'd like to try to debug and offer a PR

sounds great!

[sharkdp]

@tpiekarski It's probably not completely trivial. We might need to set AppSettings::DisableHelpFlags and then implement -h/--help ourselves via App::write_help after checking the --color value and setting ColorAlways/ColorNever appropriately.

But maybe I'm missing something.

[tpiekarski]

@sharkdp Thanks for taking a closer look.
However I'll take my chances today/tomorrow and try to solve this issue.
Should I have questions I know I can ask them here.

[tpiekarski]

@tpiekarski It's probably not completely trivial. We might need to set AppSettings::DisableHelpFlags and then implement -h/--help ourselves via App::write_help after checking the --color value and setting ColorAlways/ColorNever appropriately.

Indeed it does not look straight forward at all. But I got an idea how it could be accomplished without providing a custom function for -h / --help.

In app.rs#L7 AppSettings::ColoredHelp could be set at runtime, based upon the value provided by --color|-c and for the error message clap offers AppSettings::ColorNever for never using color at all, see settings.rs#L574.

The only issue I did not yet figured out is, how it could be possible to check the argument color without being able to parse the arguments with get_matches(). Got to dig a little deeper into clap. Could this be an alternative approach?

[sharkdp]

The only issue I did not yet figured out is, how it could be possible to check the argument color without being able to parse the arguments with get_matches(). Got to dig a little deeper into clap. Could this be an alternative approach?

That's why I suggested the approach above. We will not be able to set ColorNever after we already built the App and executed app_matches(). The help text will be printed inside app_matches(). It's already too late then.

It might be worth asking this question in the clap repo (or checking if it has already been addressed), since it seems to be a common use case.

[tpiekarski]

Alright, I suspected that you checked such solution already. None the less I wanted to take a look into the issue. I am not so much in favor to rewrite App::write_help, but if you want to, please go ahead.

Indeed there is an open issue at clap for the very feature we've been talking about Partial / Pre Parsing a CLI.

What do you think we track this issue and return to this here when it is possible to pre-parsing arguments? To be frank I'm not confident to look into the issue at clap myself - I am not experienced enough with Rust. Maybe you've got the time to take a closer look there.

[sharkdp]

I guess we could at least implement the NO_COLOR variant of this. If NO_COLOR is set, we can simply pass ColorNever.

[sharkdp]

this is how we do it in bat: https://github.com/sharkdp/bat/blob/c3ec92a13fe051142ab23d8a5521ab18115bd5dd/src/bin/bat/clap_app.rs#L6-L10

[sharkdp]

fix released in v8.2.0.