Can't get colors to print...

[cylewitruk]

Clap 4.5.3

I've tried for a couple of days now and haven't been able to get colors to print in help. I've scoured the internets and issues/discussions in this repo and the most promising solution for v4 seems to be something like this stackoverflow -- I've tried this and several other variants, but alas... no color.

And yes, colors do work fine in my terminal as I'm printing colors elsewhere 😄

I'm using #[clap(styles=styles())] on my "top-level" command struct, where styles() is:

fn styles() -> Styles {
    Styles::styled()
        .header(AnsiColor::Red.on_default() | Effects::BOLD)
        .usage(AnsiColor::Red.on_default() | Effects::BOLD)
        .literal(AnsiColor::Blue.on_default() | Effects::BOLD)
        .placeholder(AnsiColor::Green.on_default())
}

I've also tried both Always and Auto color modes... Others seem to be getting it to work this way, but I'm having no luck using styling.

Is there something I'm blatantly missing? Examples are a little short in this area it feels..

[epage]

Could you provide a reproduction case?

[cylewitruk]

Sure -- reproduction repo here.

I'm probably missing something silly...

[epage]

Note that the following works:

fn main() -> Result<()> {
    let cli = Cli::parse();
    match cli.command {
        MySubCommands::Foo(_) => {
            println!("Running foo");
        }
        MySubCommands::Bar => {
            println!("Running bar");
        }
    }

    Ok(())
}

To better understand why that works but it doesn't work in your case, let me create a middle ground. The above is almost but not quite

fn main() -> Result<()> {
    match Cli::try_parse() {
        Ok(cli) => match cli.command {
            MySubCommands::Foo(_) => {
                println!("Running foo");
            }
            MySubCommands::Bar => {
                println!("Running bar");
            }
        },
        Err(err) => {
            eprintln!("{}", err.render().ansi());
            std::process::exit(1);
        }
    }

    Ok(())
}

What is happening is that the impl Display for Error strips the colors for maximum compatibility with expectations for Display. You have to explicitly opt-in to those expectations with .ansi(). This means you will always print colors.

What you likely want instead is err.print(); as that will use our internal logic to determine when to print colors. Alternatively, you could use anstream::stderr() like we do.

[cylewitruk]

e.print(); works perfectly, thanks!

Was this highlighted somewhere in the docs that I missed? Might be worth tossing in a small "colors" example with comments highlighting the above as it seems pretty easy to miss, and I think a lot of people look to the examples first (at least I do) 😄

[epage]

We generally have the examples pushing people towards parse, rather than try_parse and everything will just work in those cases. try_parse and the other variants are for more specialized use cases and its a bit of a confluence of events to run into this situation, making it hard to pin point a specific place to cover this.

[cylewitruk]

Aha, perhaps a note in try_parse that it's generally recommended to use parse unless the application has specific requirements for handling parsing errors vs. clap's own logic, and that it may affect clap's default rendering -- or something like that :)