clap::Error to colored string

[sigoden]

Please complete the following tasks

• I have searched the discussions
• I have searched the open and rejected issues

Clap Version

master

Describe your use case

I make a bash cli tool(https://github.com/sigoden/argc), it use clap as cli parser.

A pr(sigoden/argc#37) have been submitted for request colored help and colored error message.

So I need a way to covert clap::Error to colored string.

Describe the solution you'd like

The easiest way is to expose following two apis.

1. clap::error::Error::formatted

2. clap::builder::StyledStr::write_colored

A better way is to add a to_color_string function to clap::error::Error

impl Error {
    #[cfg(feature = "color")]
    pub fn to_colored_string(&self) -> String {

    }
}

Alternatives, if applicable

No response

Additional Context

No response

[epage]

Is there a reason you can't just use Error::print or Error::exit?

In clap 4.x, we are planning on changing how we handle terminal styling which will lead to use exposing something like what is proposed in here.

[sigoden]

Argc use bash eval $(argc --argc-eval "$0" "$@") to retrive passed variables from stdout, so the help text or error message must print to stderr.

Error::print or Error::exit will print to stdout in some situation(ErrorKind::DisplayHelp | ErrorKind::DisplayVersion). So I can't use them.

[epage]

Error::print or Error::exit will print to stdout in some situation(ErrorKind::DisplayHelp | ErrorKind::DisplayVersion). So I can't use them.

In the interim, you can check the error kind and conditionally do it based on that.

[sigoden]

But I still need to print help(ErrorKind::DisplayHelp) to stderr. Is there a way to get the colored help string?

[epage]

No, and there won't be until some time during clap 4.x.

I was providing a way to workaround the problem until we do provide an API for this. This is my top clap priority once 4.0 is released.

[epage]

Went ahead with this in #4248