Example usage of arg_enum in Clap 3.0.0-beta.2

Cargo.toml

[package]
name = "clap-argenum-for-ed"
version = "0.1.0"
edition = "2021"

# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

[dependencies]
clap = "= 3.0.0-beta.2"
clap_derive = " = 3.0.0-beta.2"
thiserror = "1.0.30"

main.rs

use std::str::FromStr;

use clap::Clap;

#[derive(Debug, thiserror::Error)]
pub enum MyError {
    #[error("Error parsing enum: `{0}`")]
    EnumParseError(String),
}

/// Specifies which region should be captured.
#[derive(Debug, Clone, Clap)]
pub enum CaptureRegion {
    /// The entire history.
    ///
    /// This will end up sending `-S - -E -` to `tmux capture-pane`.
    EntireHistory,
    /// The visible area.
    VisibleArea,
}

impl FromStr for CaptureRegion {
    type Err = MyError;

    fn from_str(s: &str) -> Result<Self, MyError> {
        match s {
            "entire-history" => Ok(CaptureRegion::EntireHistory),
            "visible-area" => Ok(CaptureRegion::VisibleArea),
            _ => Err(MyError::EnumParseError(format!(
                "entire-history or visible-area, got {}",
                s
            ))),
        }
    }
}

/// Main configuration, parsed from command line.
#[derive(Clap, Debug)]
#[clap(author, about, version)]
pub struct Config {
    /// Specifies which region of the terminal buffer to capture.
    #[clap(arg_enum, default_value = "visible-area")]
    pub capture_region: CaptureRegion,
}

fn main() {
    let _ = Config::parse();
}

Thanks Ed for the explanation! It confirms my previous vague understanding of it.

I'll now open an issue for long_about.

I upgraded the code to beta5 and did not see any conflicts.

Sounds surprising to me, as I spent some time adapting to beta.5, but granted I'm not very experienced with Rust. Nevermind.

Best