rust/chg/src/uihandler.rs

worker: do not swallow exception occurred in main process

Before, SystemExit(255) would be most likely raised since the worker processes
were terminated by the main process and the status would be set to 255 in
response. We should instead re-raise the exception occurred first. It's pretty
hard to debug problems like the issue 6035 with no traceback.

// 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.

use futures::Future;
use futures::future::IntoFuture;
use std::io;
use std::os::unix::io::AsRawFd;
use std::os::unix::process::ExitStatusExt;
use std::process::{Command, Stdio};
use tokio;
use tokio_process::{ChildStdin, CommandExt};

use super::message::CommandSpec;
use super::procutil;

/// Callback to process shell command requests received from server.
pub trait SystemHandler: Sized {
    type PagerStdin: AsRawFd;
    type SpawnPagerResult: IntoFuture<Item = (Self, Self::PagerStdin), Error = io::Error>;
    type RunSystemResult: IntoFuture<Item = (Self, i32), Error = io::Error>;

    /// Handles pager command request.
    ///
    /// Returns the pipe to be attached to the server if the pager is spawned.
    fn spawn_pager(self, spec: CommandSpec) -> Self::SpawnPagerResult;

    /// Handles system command request.
    ///
    /// Returns command exit code (positive) or signal number (negative).
    fn run_system(self, spec: CommandSpec) -> Self::RunSystemResult;
}

/// Default cHg implementation to process requests received from server.
pub struct ChgUiHandler {
}

impl ChgUiHandler {
    pub fn new() -> ChgUiHandler {
        ChgUiHandler {}
    }
}

impl SystemHandler for ChgUiHandler {
    type PagerStdin = ChildStdin;
    type SpawnPagerResult = io::Result<(Self, Self::PagerStdin)>;
    type RunSystemResult = Box<dyn Future<Item = (Self, i32), Error = io::Error> + Send>;

    fn spawn_pager(self, spec: CommandSpec) -> Self::SpawnPagerResult {
        let mut pager = new_shell_command(&spec)
            .stdin(Stdio::piped())
            .spawn_async()?;
        let pin = pager.stdin().take().unwrap();
        procutil::set_blocking_fd(pin.as_raw_fd())?;
        // TODO: if pager exits, notify the server with SIGPIPE immediately.
        // otherwise the server won't get SIGPIPE if it does not write
        // anything. (issue5278)
        // kill(peerpid, SIGPIPE);
        tokio::spawn(pager.map(|_| ()).map_err(|_| ()));  // just ignore errors
        Ok((self, pin))
    }

    fn run_system(self, spec: CommandSpec) -> Self::RunSystemResult {
        let fut = new_shell_command(&spec)
            .spawn_async()
            .into_future()
            .flatten()
            .map(|status| {
                let code = status.code().or_else(|| status.signal().map(|n| -n))
                    .expect("either exit code or signal should be set");
                (self, code)
            });
        Box::new(fut)
    }
}

fn new_shell_command(spec: &CommandSpec) -> Command {
    let mut builder = Command::new("/bin/sh");
    builder
        .arg("-c")
        .arg(&spec.command)
        .current_dir(&spec.current_dir)
        .env_clear()
        .envs(spec.envs.iter().cloned());
    builder
 }