rust/chg/src/main.rs

rust-chg: spawn server process if not running

This is the minimal reimplementation of gethgcmd(), execcmdserver(),
retryconnectcmdserver(), and connectcmdserver() in chg.c.

No config validation is implemented yet. And some Py3 workarounds would
be missing as this is the code I wrote in 2018.

Differential Revision: https://phab.mercurial-scm.org/D8360

// Copyright 2018 Yuya Nishihara <[e-mail]>
//
// This software may be used and distributed according to the terms of the
// GNU General Public License version 2 or any later version.

extern crate chg;
extern crate futures;
extern crate log;
extern crate tokio;
extern crate tokio_hglib;

use chg::locator::Locator;
use chg::procutil;
use chg::{ChgClientExt, ChgUiHandler};
use futures::sync::oneshot;
use std::env;
use std::io;
use std::process;
use std::time::Instant;
use tokio::prelude::*;

struct DebugLogger {
    start: Instant,
}

impl DebugLogger {
    pub fn new() -> DebugLogger {
        DebugLogger {
            start: Instant::now(),
        }
    }
}

impl log::Log for DebugLogger {
    fn enabled(&self, metadata: &log::Metadata) -> bool {
        metadata.target().starts_with("chg::")
    }

    fn log(&self, record: &log::Record) {
        if self.enabled(record.metadata()) {
            // just make the output looks similar to chg of C
            let l = format!("{}", record.level()).to_lowercase();
            let t = self.start.elapsed();
            writeln!(
                io::stderr(),
                "chg: {}: {}.{:06} {}",
                l,
                t.as_secs(),
                t.subsec_micros(),
                record.args()
            )
            .unwrap_or(());
        }
    }

    fn flush(&self) {}
}

fn main() {
    if env::var_os("CHGDEBUG").is_some() {
        log::set_boxed_logger(Box::new(DebugLogger::new()))
            .expect("any logger should not be installed yet");
        log::set_max_level(log::LevelFilter::Debug);
    }

    // TODO: add loop detection by $CHGINTERNALMARK

    let code = run().unwrap_or_else(|err| {
        writeln!(io::stderr(), "chg: abort: {}", err).unwrap_or(());
        255
    });
    process::exit(code);
}

fn run() -> io::Result<i32> {
    let current_dir = env::current_dir()?;
    let loc = Locator::prepare_from_env()?;
    let handler = ChgUiHandler::new();
    let (result_tx, result_rx) = oneshot::channel();
    let fut = loc
        .connect()
        .and_then(|(_, client)| client.set_current_dir(current_dir))
        .and_then(|client| client.attach_io(io::stdin(), io::stdout(), io::stderr()))
        .and_then(|client| {
            let pid = client.server_spec().process_id.unwrap();
            let pgid = client.server_spec().process_group_id;
            procutil::setup_signal_handler_once(pid, pgid)?;
            Ok(client)
        })
        .and_then(|client| client.run_command_chg(handler, env::args_os().skip(1)))
        .map(|(_client, _handler, code)| {
            procutil::restore_signal_handler_once()?;
            Ok(code)
        })
        .or_else(|err| Ok(Err(err))) // pass back error to caller
        .map(|res| result_tx.send(res).unwrap());
    tokio::run(fut);
    result_rx.wait().unwrap_or(Err(io::Error::new(
        io::ErrorKind::Other,
        "no exit code set",
    )))
}