How to load binaries like cargo-web.exe in Clap?

hydroper · December 22, 2018, 4:11pm

Is it possible to interrupt parsing after astro air, for example, once it ultrapasses 'air'?

extern crate clap;
use clap::{App, Arg, ArgGroup, SubCommand};

// mod config;
// mod storage;

fn main() {
    let app = App::new("Astro")
        .version("0.1.0")
        .subcommand(SubCommand::with_name("new")
            .group(ArgGroup::with_name("type")
                .required(true))
            .arg(Arg::from_usage("--bin [dev-type]").group("type"))
            .arg(Arg::from_usage("--lib [dev-type]").group("type"))
            .arg_from_usage("<name>"))
        .subcommand(SubCommand::with_name("air"));

    // Got to figure in how to add sym-link
    // commands w/ clap.
//  storage::devtools::commands(&app);

    let matches = app.get_matches();

    match matches.subcommand_name() {
        Some("new") => println!("Rant new"),
        Some("air") => println!("{}", std::env::args().nth(0).unwrap().as_str()),
        None => (),
        _ => println!("Missing impl")
    }
}

Not really working.

hydroper · December 22, 2018, 6:58pm

So far I didn’t find anything related in Cargo’s source (this is where all the CLI goes). To clarify I want to know how cargo web works. How does cargo-web.exe runs as a subcommand in cargo if it’s not a built-in one?

It looks like my GitHub issue won’t be answered too and I’m not wanting to waste time again like my threwn away parsers.

daboross · December 22, 2018, 10:05pm

If I’m reading the source correctly, cargo matches on clap errors and if it’s an unrecognized subcommand, it will try to execute an external binary cargo-<subcommandname>:

github.com

rust-lang/cargo/blob/41a7e150fcd6191afec6425cb024ccae60d71cd2/src/bin/cargo/cli.rs#L15


use cargo::{self, CliResult, Config};


use super::commands;
use super::list_commands;
use crate::command_prelude::*;


pub fn main(config: &mut Config) -> CliResult {
let args = match cli().get_matches_safe() {
    Ok(args) => args,
    Err(e) => {
        if e.kind == clap::ErrorKind::UnrecognizedSubcommand {
            // An unrecognized subcommand might be an external subcommand.
            let cmd = &e.info.as_ref().unwrap()[0].to_owned();
            return super::execute_external_subcommand(config, cmd, &[cmd, "--help"])
                .map_err(|_| e.into());
        } else {
            return Err(e)?;
        }
    }
};

and execute_external_subcommand:

github.com

rust-lang/cargo/blob/41a7e150fcd6191afec6425cb024ccae60d71cd2/src/bin/cargo/main.rs#L140-L177


fn execute_external_subcommand(config: &Config, cmd: &str, args: &[&str]) -> CliResult {
let command_exe = format!("cargo-{}{}", cmd, env::consts::EXE_SUFFIX);
let path = search_directories(config)
    .iter()
    .map(|dir| dir.join(&command_exe))
    .find(|file| is_executable(file));
let command = match path {
    Some(command) => command,
    None => {
        let err = match find_closest(config, cmd) {
            Some(closest) => format_err!(
                "no such subcommand: `{}`\n\n\tDid you mean `{}`?\n",
                cmd,
                closest
            ),
            None => format_err!("no such subcommand: `{}`", cmd),
        };
        return Err(CliError::new(err, 101));
    }
};

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There’s probably more to it than just this, but the rest can probably be found by digging around in cargo’s source searching for usages of execute_external_subcommand and the like?

hydroper · December 26, 2018, 9:53am

It’s not always ::UnrecognizedSubcommand, so…

if let Err(err) = result {
        match err.kind {
              ErrorKind::UnrecognizedSubcommand
            | ErrorKind::UnknownArgument => {
                let name = &err.info.unwrap()[0];
                println!("Probably air");
                return;
            },
            _ => {
                if err.use_stderr() {
                    err.exit();
                }
                return;
            }
        }
    }