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use clap::Parser;
#[derive(Parser, Debug, PartialEq)]
#[clap(author, version, about, long_about = None)]
struct Opt {
// Default parser for `Set` is FromStr::from_str.
// `impl FromStr for bool` parses `true` or `false` so this
// works as expected.
#[clap(long, action = clap::ArgAction::Set)]
foo: bool,
// Of course, this could be done with an explicit parser function.
#[clap(long, action = clap::ArgAction::Set, value_parser = true_or_false, default_value_t)]
bar: bool,
// `bool` can be positional only with explicit `action` annotation
#[clap(action = clap::ArgAction::Set)]
boom: bool,
}
fn true_or_false(s: &str) -> Result<bool, &'static str> {
match s {
"true" => Ok(true),
"false" => Ok(false),
_ => Err("expected `true` or `false`"),
}
}
fn main() {
let opt = Opt::parse();
dbg!(opt);
}
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