clap-repl

One of the typical user interfaces for prompting commands is the repl (read eval print loop). One of the best ways of representing commands in a repl is using space separated arguments, which is what terminal shells do. And the way to parse such commands in Rust is the clap crate. This crate uses clap and rustyline to provide such user interface in a way that you only focus on your app logic.

Features

Thanks to clap and rustyline this crate handles:

• Parsing the space separated commands into your data structure.
• Help flag for each command.
• Verifying the command is valid, generating useful errors and suggestions otherwise.
• Auto complete and hint for the commands.

Example

use clap::Parser;
use clap_repl::ClapEditor;
use console::style;
use rustyline::DefaultEditor;

#[derive(Debug, Parser)]
#[command(name = "")] // This name will show up in clap's error messages, so it is important to set it to "".
enum SampleCommand {
    Download {
        path: String,
        /// Some explanation about what this flag do.
        #[arg(long)]
        check_sha: bool,
    },
    /// A command to upload things.
    Upload,
    Login {
        /// Optional. You will be prompted if you don't provide it.
        #[arg(short, long)]
        username: Option<String>,
    },
}

fn main() {
    // Use `ClapEditor` instead of the `rustyline::DefaultEditor`.
    let mut rl = ClapEditor::<SampleCommand>::new();
    loop {
        // Use `read_command` instead of `readline`.
        let Some(command) = rl.read_command() else {
            continue;
        };
        match command {
            SampleCommand::Download { path, check_sha } => {
                println!("Downloaded {path} with checking = {check_sha}");
            },
            SampleCommand::Upload => {
                println!("Uploaded");
            },
            SampleCommand::Login { username } => {
                // You can use another `rustyline::Editor` inside the loop.
                let mut rl = DefaultEditor::new().unwrap();
                let username = username.unwrap_or_else(|| rl.readline(&style("What is your username? ").bold().to_string()).unwrap());
                let password = rl.readline(&style("What is your password? ").bold().to_string()).unwrap();
                println!("Logged in with {username} and {password}");
            },
        }
    }
}