use clap::Parser; #[derive(Parser)] #[clap(name = "cargo")] #[clap(bin_name = "cargo")] enum Cargo { ExampleDerive(ExampleDerive), } #[derive(clap::Args)] #[clap(about, author, version)] struct ExampleDerive { #[clap(long, parse(from_os_str))] manifest_path: Option, } fn main() { let Cargo::ExampleDerive(args) = Cargo::parse(); println!("{:?}", args.manifest_path); }