How do I parse only a subset of arguments?

[NikitaSkrynnik]

Hi! This code gives me an empty Arguments struct. How do I fix it? I can't change the order of arguments.

use clap::{CommandFactory, FromArgMatches, Parser};
use std::path::PathBuf;

#[derive(Parser, Default, Debug)]
struct Arguments {
    #[arg(long, default_value = "8080")]
    port: u16,

    #[arg(long, default_value = "")]
    cache_path: PathBuf,

    #[arg(long, default_value = "")]
    root_cache_path: PathBuf,
}

fn main() {
    // Simulated argv
    let argv = vec![
        "app",
        "--type=zygote",
        "--no-zygote-sandbox",
        "--string-annotations",
        "--enable-crash-reporter=,",
        "--change-stack-guard-on-fork=enable",
        "--user-data-dir=/tmp/mycache",
        "--log-severity=verbose",
        "--port=8080",
        "--cache-path=/tmp/aa",
        "--root-cache-path=/tmp/bb",
    ];

    let matches = Arguments::command()
        .ignore_errors(true)
        .get_matches_from(argv);
    let args = Arguments::from_arg_matches(&matches).unwrap_or_default();

    println!("{:?}", args);
}

Output:

Arguments { port: 0, cache_path: "", root_cache_path: "" }

[epage]

#[command(ignore_errors = true)] is currently the best solution we have to offer for this.

Looks like you are already using it and its still failing. Actually looking at the error, we get

error: The following required argument was not provided: cache_path

Usage: playground [OPTIONS]

For more information, try '--help'.

This is coming from trying to populate the fields in Arguments. This means that default_value did not apply for some reason.

The relevant issues for this are #4391