Parse non-empty string values

See also:

• ValueParser::string

Example

Usage:

# use clap_builder as clap;
let mut cmd = clap::Command::new("raw")
    .arg(
        clap::Arg::new("append")
            .value_parser(clap::builder::NonEmptyStringValueParser::new())
            .required(true)
    );

let m = cmd.try_get_matches_from_mut(["cmd", "true"]).unwrap();
let port: &String = m.get_one("append")
    .expect("required");
assert_eq!(port, "true");

Semantics:

# use clap_builder as clap;
# use std::ffi::OsStr;
# use clap::builder::TypedValueParser;
# let cmd = clap::Command::new("test");
# let arg = None;
let value_parser = clap::builder::NonEmptyStringValueParser::new();
assert_eq!(value_parser.parse_ref(&cmd, arg, OsStr::new("random")).unwrap(), "random");
assert!(value_parser.parse_ref(&cmd, arg, OsStr::new("")).is_err());