UnknownArgumentValueParser eagerly errors out

[weihanglo]

Please complete the following tasks

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

Rust Version

rustc 1.72.0-beta.8 (598a0a3cb 2023-08-12)

Clap Version

4.3.22

Minimal reproducible code

#!/usr/bin/env -S cargo +nightly -Zscript

//! ```cargo
//! [dependencies]
//! clap = "=4.3.22"
//! ```

fn main() {
    let _cmd = clap::Command::new("test")
        .args([
            clap::Arg::new("ignore-rust-version")
                .long("ignore-rust-version")
                .action(clap::ArgAction::SetTrue),
            clap::Arg::new("libtest-ignore")
                .long("ignored")
                .action(clap::ArgAction::SetTrue)
                .value_parser(
                    clap::builder::UnknownArgumentValueParser::suggest_arg("-- --ignored")
                        .and_suggest("not much else to say"),
                )
                .hide(true),
        ])
        .get_matches();
}

Steps to reproduce the bug with the above code

See above cargo script.

Actual Behaviour

$ cargo +nightly -Zscript clap-unknown-suggest-bug.rs

error: unexpected argument '--ignored' found

  tip: a similar argument exists: '-- --ignored'
  tip: not much else to say

Usage: clap-unknown-suggest-bug [OPTIONS]

For more information, try '--help'.

Expected Behaviour

Should not fail

Additional Context

cc #5075

Sorry I wasn't familiar with codebase enough to detect this bug during the review 😞.

Debug Output

No response

[epage]

I had thought of this case but forgot it. The issue is we model a flag being present as a default_missing_value and not being present with default_value. In either case, we end up parsing a value.

A fix and new release will be available shortly

[weihanglo]

Thanks a lot!

BTW, I feel the power of cargo-script 💪🏾.