view rust/chg/src/uihandler.rs @ 51634:3b69324d9535 stable

exchange: fix locking to actually be scoped

The previous code was taking locks before entering with statements, so
exception before the with statement would not release the lock (except for
garbage collection).

We need to move to a try except here because the logic is more complicated.

// 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 async_trait::async_trait;
use std::io;
use std::os::unix::io::AsRawFd;
use std::os::unix::process::ExitStatusExt;
use std::process::Stdio;
use tokio;
use tokio::process::{Child, ChildStdin, Command};

use crate::message::CommandSpec;
use crate::procutil;

/// Callback to process shell command requests received from server.
#[async_trait]
pub trait SystemHandler {
    type PagerStdin: AsRawFd;

    /// Handles pager command request.
    ///
    /// Returns the pipe to be attached to the server if the pager is spawned.
    async fn spawn_pager(
        &mut self,
        spec: &CommandSpec,
    ) -> io::Result<Self::PagerStdin>;

    /// Handles system command request.
    ///
    /// Returns command exit code (positive) or signal number (negative).
    async fn run_system(&mut self, spec: &CommandSpec) -> io::Result<i32>;
}

/// Default cHg implementation to process requests received from server.
pub struct ChgUiHandler {
    pager: Option<Child>,
}

impl ChgUiHandler {
    pub fn new() -> ChgUiHandler {
        ChgUiHandler { pager: None }
    }

    /// Waits until the pager process exits.
    pub async fn wait_pager(&mut self) -> io::Result<()> {
        if let Some(p) = self.pager.take() {
            p.await?;
        }
        Ok(())
    }
}

#[async_trait]
impl SystemHandler for ChgUiHandler {
    type PagerStdin = ChildStdin;

    async fn spawn_pager(
        &mut self,
        spec: &CommandSpec,
    ) -> io::Result<Self::PagerStdin> {
        let mut pager =
            new_shell_command(&spec).stdin(Stdio::piped()).spawn()?;
        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);
        self.pager = Some(pager);
        Ok(pin)
    }

    async fn run_system(&mut self, spec: &CommandSpec) -> io::Result<i32> {
        let status = new_shell_command(&spec).spawn()?.await?;
        let code = status
            .code()
            .or_else(|| status.signal().map(|n| -n))
            .expect("either exit code or signal should be set");
        Ok(code)
    }
}

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
}