How do I allow uppercase flags in Clap?

Question

For my RUST program, I am using Clap to parse my command line arguments. I want to let users input flags like so:

my_program -L testfile.txt

I set up my struct like so:

struct Args {
    #[arg(short)]
    L: bool,

    #[arg(short)]
    s: bool,

    name: String,
}

When I test out my program, it gives me this error:

error: Found argument '-L' which wasn't expected, or isn't valid in this context.

I can't use ignore_case() either, since this is a flag and doesn't take a value.

Does anyone know how to solve this problem?

Answer 1

From Arg Attributes in the clap derive documentation:

short [= <char>]: Arg::short

• When not present: no short set
• Without <char>: defaults to first character in the case-converted field name

use clap::Parser;

#[derive(Parser)]
#[command(author, version, about, long_about = None)]
struct Cli {
    #[arg(short = 'L')]
    L: bool,

    #[arg(short)]
    s: bool,

    name: String,
}

fn main() {
    let args = Cli::parse();
}

Built executable help:

Usage: xxxxxx [OPTIONS] <NAME>

Arguments:
  <NAME>

Options:
  -L
  -s
  -h, --help     Print help information
  -V, --version  Print version information