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https://github.com/clap-rs/clap
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eda0ca54c1
Clap has focused on reporting development errors through assertions rather than mixing user errors with development errors. Sometimes, developers need to handle things more flexibly so included in #3732 was the reporting of value accessor failures as internal errors with a distinct type. I've been going back and forth on whether the extra error pessimises the usability in the common case vs dealing with the proliferation of different function combinations. In working on deprecating the `value_of` functions, I decided that it was going to be worth duplicating so long as we can keep the documentation focused.
38 lines
971 B
Rust
38 lines
971 B
Rust
// Note: this requires the `cargo` feature
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use std::ops::RangeInclusive;
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use clap::{arg, command};
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fn main() {
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let matches = command!()
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.arg(
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arg!(<PORT>)
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.help("Network port to use")
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.value_parser(port_in_range),
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)
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.get_matches();
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// Note, it's safe to call unwrap() because the arg is required
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let port: u16 = *matches
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.get_one::<u16>("PORT")
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.expect("'PORT' is required and parsing will fail if its missing");
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println!("PORT = {}", port);
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}
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const PORT_RANGE: RangeInclusive<usize> = 1..=65535;
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fn port_in_range(s: &str) -> Result<u16, String> {
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let port: usize = s
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.parse()
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.map_err(|_| format!("`{}` isn't a port number", s))?;
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if PORT_RANGE.contains(&port) {
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Ok(port as u16)
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} else {
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Err(format!(
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"Port not in range {}-{}",
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PORT_RANGE.start(),
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PORT_RANGE.end()
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))
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}
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}
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