rust-chg: upgrade to 2018 edition and remove useless extern crates

Differential Revision: https://phab.mercurial-scm.org/D8399

rust/chg/Cargo.toml

@@ -1,19 +1,20 b''
 [package]
 name = "chg"
 version = "0.1.0"
 authors = ["Yuya Nishihara <[e-mail]>"]
 description = "Client for Mercurial command server with cHg extension"
 license = "GPL-2.0+"
+edition = "2018"
 
 [dependencies]
 bytes = "0.4"
 futures = "0.1"
 libc = "0.2"
 log = { version = "0.4", features = ["std"] }
 tokio = "0.1"
 tokio-hglib = "0.2"
 tokio-process = "0.2.3"
 tokio-timer = "0.2"
 
 [build-dependencies]
 cc = "1.0"

rust/chg/build.rs

@@ -1,9 +1,7 b''
-extern crate cc;
-
 fn main() {
     cc::Build::new()
         .warnings(true)
         .file("src/sendfds.c")
         .file("src/sighandlers.c")
         .compile("procutil");
 }

rust/chg/src/attachio.rs

@@ -1,114 +1,114 b''
 // 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.
 
 //! Functions to send client-side fds over the command server channel.
 
-use futures::{Async, Future, Poll};
+use futures::{try_ready, Async, Future, Poll};
 use std::io;
 use std::os::unix::io::AsRawFd;
 use tokio_hglib::codec::ChannelMessage;
 use tokio_hglib::protocol::MessageLoop;
 use tokio_hglib::{Client, Connection};
 
 use super::message;
 use super::procutil;
 
 /// Future to send client-side fds over the command server channel.
 ///
 /// This works as follows:
 /// 1. Client sends "attachio" request.
 /// 2. Server sends back 1-byte input request.
 /// 3. Client sends fds with 1-byte dummy payload in response.
 /// 4. Server returns the number of the fds received.
 ///
 /// If the stderr is omitted, it will be redirected to the stdout. This
 /// allows us to attach the pager stdin to both stdout and stderr, and
 /// dispose of the client-side handle once attached.
 #[must_use = "futures do nothing unless polled"]
 pub struct AttachIo<C, I, O, E>
 where
     C: Connection,
 {
     msg_loop: MessageLoop<C>,
     stdin: I,
     stdout: O,
     stderr: Option<E>,
 }
 
 impl<C, I, O, E> AttachIo<C, I, O, E>
 where
     C: Connection + AsRawFd,
     I: AsRawFd,
     O: AsRawFd,
     E: AsRawFd,
 {
     pub fn with_client(
         client: Client<C>,
         stdin: I,
         stdout: O,
         stderr: Option<E>,
     ) -> AttachIo<C, I, O, E> {
         let msg_loop = MessageLoop::start(client, b"attachio");
         AttachIo {
             msg_loop,
             stdin,
             stdout,
             stderr,
         }
     }
 }
 
 impl<C, I, O, E> Future for AttachIo<C, I, O, E>
 where
     C: Connection + AsRawFd,
     I: AsRawFd,
     O: AsRawFd,
     E: AsRawFd,
 {
     type Item = Client<C>;
     type Error = io::Error;
 
     fn poll(&mut self) -> Poll<Self::Item, Self::Error> {
         loop {
             let (client, msg) = try_ready!(self.msg_loop.poll());
             match msg {
                 ChannelMessage::Data(b'r', data) => {
                     let fd_cnt = message::parse_result_code(data)?;
                     if fd_cnt == 3 {
                         return Ok(Async::Ready(client));
                     } else {
                         return Err(io::Error::new(
                             io::ErrorKind::InvalidData,
                             "unexpected attachio result",
                         ));
                     }
                 }
                 ChannelMessage::Data(..) => {
                     // just ignore data sent to uninteresting (optional) channel
                     self.msg_loop = MessageLoop::resume(client);
                 }
                 ChannelMessage::InputRequest(1) => {
                     // this may fail with EWOULDBLOCK in theory, but the
                     // payload is quite small, and the send buffer should
                     // be empty so the operation will complete immediately
                     let sock_fd = client.as_raw_fd();
                     let ifd = self.stdin.as_raw_fd();
                     let ofd = self.stdout.as_raw_fd();
                     let efd = self.stderr.as_ref().map_or(ofd, |f| f.as_raw_fd());
                     procutil::send_raw_fds(sock_fd, &[ifd, ofd, efd])?;
                     self.msg_loop = MessageLoop::resume(client);
                 }
                 ChannelMessage::InputRequest(..)
                 | ChannelMessage::LineRequest(..)
                 | ChannelMessage::SystemRequest(..) => {
                     return Err(io::Error::new(
                         io::ErrorKind::InvalidData,
                         "unsupported request while attaching io",
                     ));
                 }
             }
         }
     }
 }

rust/chg/src/lib.rs

@@ -1,26 +1,15 b''
 // 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 bytes;
-#[macro_use]
-extern crate futures;
-extern crate libc;
-#[macro_use]
-extern crate log;
-extern crate tokio;
-extern crate tokio_hglib;
-extern crate tokio_process;
-extern crate tokio_timer;
-
 mod attachio;
 mod clientext;
 pub mod locator;
 pub mod message;
 pub mod procutil;
 mod runcommand;
 mod uihandler;
 
 pub use clientext::ChgClientExt;
 pub use uihandler::{ChgUiHandler, SystemHandler};

rust/chg/src/locator.rs

@@ -1,500 +1,501 b''
 // Copyright 2011, 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.
 
 //! Utility for locating command-server process.
 
 use futures::future::{self, Either, Loop};
+use log::debug;
 use std::env;
 use std::ffi::{OsStr, OsString};
 use std::fs::{self, DirBuilder};
 use std::io;
 use std::os::unix::ffi::{OsStrExt, OsStringExt};
 use std::os::unix::fs::{DirBuilderExt, MetadataExt};
 use std::path::{Path, PathBuf};
 use std::process::{self, Command};
 use std::time::Duration;
 use tokio::prelude::*;
 use tokio_hglib::UnixClient;
 use tokio_process::{Child, CommandExt};
 use tokio_timer;
 
 use super::clientext::ChgClientExt;
 use super::message::{Instruction, ServerSpec};
 use super::procutil;
 
 const REQUIRED_SERVER_CAPABILITIES: &[&str] = &[
     "attachio",
     "chdir",
     "runcommand",
     "setenv",
     "setumask2",
     "validate",
 ];
 
 /// Helper to connect to and spawn a server process.
 #[derive(Clone, Debug)]
 pub struct Locator {
     hg_command: OsString,
     hg_early_args: Vec<OsString>,
     current_dir: PathBuf,
     env_vars: Vec<(OsString, OsString)>,
     process_id: u32,
     base_sock_path: PathBuf,
     redirect_sock_path: Option<PathBuf>,
     timeout: Duration,
 }
 
 impl Locator {
     /// Creates locator capturing the current process environment.
     ///
     /// If no `$CHGSOCKNAME` is specified, the socket directory will be
     /// created as necessary.
     pub fn prepare_from_env() -> io::Result<Locator> {
         Ok(Locator {
             hg_command: default_hg_command(),
             hg_early_args: Vec::new(),
             current_dir: env::current_dir()?,
             env_vars: env::vars_os().collect(),
             process_id: process::id(),
             base_sock_path: prepare_server_socket_path()?,
             redirect_sock_path: None,
             timeout: default_timeout(),
         })
     }
 
     /// Temporary socket path for this client process.
     fn temp_sock_path(&self) -> PathBuf {
         let src = self.base_sock_path.as_os_str().as_bytes();
         let mut buf = Vec::with_capacity(src.len() + 6); // "{src}.{pid}".len()
         buf.extend_from_slice(src);
         buf.extend_from_slice(format!(".{}", self.process_id).as_bytes());
         OsString::from_vec(buf).into()
     }
 
     /// Specifies the arguments to be passed to the server at start.
     pub fn set_early_args<I, P>(&mut self, args: I)
     where
         I: IntoIterator<Item = P>,
         P: AsRef<OsStr>,
     {
         self.hg_early_args = args.into_iter().map(|a| a.as_ref().to_owned()).collect();
     }
 
     /// Connects to the server.
     ///
     /// The server process will be spawned if not running.
     pub fn connect(self) -> impl Future<Item = (Self, UnixClient), Error = io::Error> {
         future::loop_fn((self, 0), |(loc, cnt)| {
             if cnt < 10 {
                 let fut = loc
                     .try_connect()
                     .and_then(|(loc, client)| {
                         client
                             .validate(&loc.hg_early_args)
                             .map(|(client, instructions)| (loc, client, instructions))
                     })
                     .and_then(move |(loc, client, instructions)| {
                         loc.run_instructions(client, instructions, cnt)
                     });
                 Either::A(fut)
             } else {
                 let msg = format!(
                     concat!(
                         "too many redirections.\n",
                         "Please make sure {:?} is not a wrapper which ",
                         "changes sensitive environment variables ",
                         "before executing hg. If you have to use a ",
                         "wrapper, wrap chg instead of hg.",
                     ),
                     loc.hg_command
                 );
                 Either::B(future::err(io::Error::new(io::ErrorKind::Other, msg)))
             }
         })
     }
 
     /// Runs instructions received from the server.
     fn run_instructions(
         mut self,
         client: UnixClient,
         instructions: Vec<Instruction>,
         cnt: usize,
     ) -> io::Result<Loop<(Self, UnixClient), (Self, usize)>> {
         let mut reconnect = false;
         for inst in instructions {
             debug!("instruction: {:?}", inst);
             match inst {
                 Instruction::Exit(_) => {
                     // Just returns the current connection to run the
                     // unparsable command and report the error
                     return Ok(Loop::Break((self, client)));
                 }
                 Instruction::Reconnect => {
                     reconnect = true;
                 }
                 Instruction::Redirect(path) => {
                     if path.parent() != self.base_sock_path.parent() {
                         let msg = format!(
                             "insecure redirect instruction from server: {}",
                             path.display()
                         );
                         return Err(io::Error::new(io::ErrorKind::InvalidData, msg));
                     }
                     self.redirect_sock_path = Some(path);
                     reconnect = true;
                 }
                 Instruction::Unlink(path) => {
                     if path.parent() != self.base_sock_path.parent() {
                         let msg = format!(
                             "insecure unlink instruction from server: {}",
                             path.display()
                         );
                         return Err(io::Error::new(io::ErrorKind::InvalidData, msg));
                     }
                     fs::remove_file(path).unwrap_or(()); // may race
                 }
             }
         }
 
         if reconnect {
             Ok(Loop::Continue((self, cnt + 1)))
         } else {
             Ok(Loop::Break((self, client)))
         }
     }
 
     /// Tries to connect to the existing server, or spawns new if not running.
     fn try_connect(self) -> impl Future<Item = (Self, UnixClient), Error = io::Error> {
         let sock_path = self
             .redirect_sock_path
             .as_ref()
             .unwrap_or(&self.base_sock_path)
             .clone();
         debug!("try connect to {}", sock_path.display());
         UnixClient::connect(sock_path)
             .then(|res| {
                 match res {
                     Ok(client) => Either::A(future::ok((self, client))),
                     Err(_) => {
                         // Prevent us from being re-connected to the outdated
                         // master server: We were told by the server to redirect
                         // to redirect_sock_path, which didn't work. We do not
                         // want to connect to the same master server again
                         // because it would probably tell us the same thing.
                         if self.redirect_sock_path.is_some() {
                             fs::remove_file(&self.base_sock_path).unwrap_or(());
                             // may race
                         }
                         Either::B(self.spawn_connect())
                     }
                 }
             })
             .and_then(|(loc, client)| {
                 check_server_capabilities(client.server_spec())?;
                 Ok((loc, client))
             })
             .and_then(|(loc, client)| {
                 // It's purely optional, and the server might not support this command.
                 if client.server_spec().capabilities.contains("setprocname") {
                     let fut = client
                         .set_process_name(format!("chg[worker/{}]", loc.process_id))
                         .map(|client| (loc, client));
                     Either::A(fut)
                 } else {
                     Either::B(future::ok((loc, client)))
                 }
             })
             .and_then(|(loc, client)| {
                 client
                     .set_current_dir(&loc.current_dir)
                     .map(|client| (loc, client))
             })
             .and_then(|(loc, client)| {
                 client
                     .set_env_vars_os(loc.env_vars.iter().cloned())
                     .map(|client| (loc, client))
             })
     }
 
     /// Spawns new server process and connects to it.
     ///
     /// The server will be spawned at the current working directory, then
     /// chdir to "/", so that the server will load configs from the target
     /// repository.
     fn spawn_connect(self) -> impl Future<Item = (Self, UnixClient), Error = io::Error> {
         let sock_path = self.temp_sock_path();
         debug!("start cmdserver at {}", sock_path.display());
         Command::new(&self.hg_command)
             .arg("serve")
             .arg("--cmdserver")
             .arg("chgunix")
             .arg("--address")
             .arg(&sock_path)
             .arg("--daemon-postexec")
             .arg("chdir:/")
             .args(&self.hg_early_args)
             .current_dir(&self.current_dir)
             .env_clear()
             .envs(self.env_vars.iter().cloned())
             .env("CHGINTERNALMARK", "")
             .spawn_async()
             .into_future()
             .and_then(|server| self.connect_spawned(server, sock_path))
             .and_then(|(loc, client, sock_path)| {
                 debug!(
                     "rename {} to {}",
                     sock_path.display(),
                     loc.base_sock_path.display()
                 );
                 fs::rename(&sock_path, &loc.base_sock_path)?;
                 Ok((loc, client))
             })
     }
 
     /// Tries to connect to the just spawned server repeatedly until timeout
     /// exceeded.
     fn connect_spawned(
         self,
         server: Child,
         sock_path: PathBuf,
     ) -> impl Future<Item = (Self, UnixClient, PathBuf), Error = io::Error> {
         debug!("try connect to {} repeatedly", sock_path.display());
         let connect = future::loop_fn(sock_path, |sock_path| {
             UnixClient::connect(sock_path.clone()).then(|res| {
                 match res {
                     Ok(client) => Either::A(future::ok(Loop::Break((client, sock_path)))),
                     Err(_) => {
                         // try again with slight delay
                         let fut = tokio_timer::sleep(Duration::from_millis(10))
                             .map(|()| Loop::Continue(sock_path))
                             .map_err(|err| io::Error::new(io::ErrorKind::Other, err));
                         Either::B(fut)
                     }
                 }
             })
         });
 
         // waits for either connection established or server failed to start
         connect
             .select2(server)
             .map_err(|res| res.split().0)
             .timeout(self.timeout)
             .map_err(|err| {
                 err.into_inner().unwrap_or_else(|| {
                     io::Error::new(
                         io::ErrorKind::TimedOut,
                         "timed out while connecting to server",
                     )
                 })
             })
             .and_then(|res| {
                 match res {
                     Either::A(((client, sock_path), server)) => {
                         server.forget(); // continue to run in background
                         Ok((self, client, sock_path))
                     }
                     Either::B((st, _)) => Err(io::Error::new(
                         io::ErrorKind::Other,
                         format!("server exited too early: {}", st),
                     )),
                 }
             })
     }
 }
 
 /// Determines the server socket to connect to.
 ///
 /// If no `$CHGSOCKNAME` is specified, the socket directory will be created
 /// as necessary.
 fn prepare_server_socket_path() -> io::Result<PathBuf> {
     if let Some(s) = env::var_os("CHGSOCKNAME") {
         Ok(PathBuf::from(s))
     } else {
         let mut path = default_server_socket_dir();
         create_secure_dir(&path)?;
         path.push("server");
         Ok(path)
     }
 }
 
 /// Determines the default server socket path as follows.
 ///
 /// 1. `$XDG_RUNTIME_DIR/chg`
 /// 2. `$TMPDIR/chg$UID`
 /// 3. `/tmp/chg$UID`
 pub fn default_server_socket_dir() -> PathBuf {
     // XDG_RUNTIME_DIR should be ignored if it has an insufficient permission.
     // https://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html
     if let Some(Ok(s)) = env::var_os("XDG_RUNTIME_DIR").map(check_secure_dir) {
         let mut path = PathBuf::from(s);
         path.push("chg");
         path
     } else {
         let mut path = env::temp_dir();
         path.push(format!("chg{}", procutil::get_effective_uid()));
         path
     }
 }
 
 /// Determines the default hg command.
 pub fn default_hg_command() -> OsString {
     // TODO: maybe allow embedding the path at compile time (or load from hgrc)
     env::var_os("CHGHG")
         .or(env::var_os("HG"))
         .unwrap_or(OsStr::new("hg").to_owned())
 }
 
 fn default_timeout() -> Duration {
     let secs = env::var("CHGTIMEOUT")
         .ok()
         .and_then(|s| s.parse().ok())
         .unwrap_or(60);
     Duration::from_secs(secs)
 }
 
 /// Creates a directory which the other users cannot access to.
 ///
 /// If the directory already exists, tests its permission.
 fn create_secure_dir<P>(path: P) -> io::Result<()>
 where
     P: AsRef<Path>,
 {
     DirBuilder::new()
         .mode(0o700)
         .create(path.as_ref())
         .or_else(|err| {
             if err.kind() == io::ErrorKind::AlreadyExists {
                 check_secure_dir(path).map(|_| ())
             } else {
                 Err(err)
             }
         })
 }
 
 fn check_secure_dir<P>(path: P) -> io::Result<P>
 where
     P: AsRef<Path>,
 {
     let a = fs::symlink_metadata(path.as_ref())?;
     if a.is_dir() && a.uid() == procutil::get_effective_uid() && (a.mode() & 0o777) == 0o700 {
         Ok(path)
     } else {
         Err(io::Error::new(io::ErrorKind::Other, "insecure directory"))
     }
 }
 
 fn check_server_capabilities(spec: &ServerSpec) -> io::Result<()> {
     let unsupported: Vec<_> = REQUIRED_SERVER_CAPABILITIES
         .iter()
         .cloned()
         .filter(|&s| !spec.capabilities.contains(s))
         .collect();
     if unsupported.is_empty() {
         Ok(())
     } else {
         let msg = format!(
             "insufficient server capabilities: {}",
             unsupported.join(", ")
         );
         Err(io::Error::new(io::ErrorKind::Other, msg))
     }
 }
 
 /// Collects arguments which need to be passed to the server at start.
 pub fn collect_early_args<I, P>(args: I) -> Vec<OsString>
 where
     I: IntoIterator<Item = P>,
     P: AsRef<OsStr>,
 {
     let mut args_iter = args.into_iter();
     let mut early_args = Vec::new();
     while let Some(arg) = args_iter.next() {
         let argb = arg.as_ref().as_bytes();
         if argb == b"--" {
             break;
         } else if argb.starts_with(b"--") {
             let mut split = argb[2..].splitn(2, |&c| c == b'=');
             match split.next().unwrap() {
                 b"traceback" => {
                     if split.next().is_none() {
                         early_args.push(arg.as_ref().to_owned());
                     }
                 }
                 b"config" | b"cwd" | b"repo" | b"repository" => {
                     if split.next().is_some() {
                         // --<flag>=<val>
                         early_args.push(arg.as_ref().to_owned());
                     } else {
                         // --<flag> <val>
                         args_iter.next().map(|val| {
                             early_args.push(arg.as_ref().to_owned());
                             early_args.push(val.as_ref().to_owned());
                         });
                     }
                 }
                 _ => {}
             }
         } else if argb.starts_with(b"-R") {
             if argb.len() > 2 {
                 // -R<val>
                 early_args.push(arg.as_ref().to_owned());
             } else {
                 // -R <val>
                 args_iter.next().map(|val| {
                     early_args.push(arg.as_ref().to_owned());
                     early_args.push(val.as_ref().to_owned());
                 });
             }
         }
     }
 
     early_args
 }
 
 #[cfg(test)]
 mod tests {
     use super::*;
 
     #[test]
     fn collect_early_args_some() {
         assert!(collect_early_args(&[] as &[&OsStr]).is_empty());
         assert!(collect_early_args(&["log"]).is_empty());
         assert_eq!(
             collect_early_args(&["log", "-Ra", "foo"]),
             os_string_vec_from(&[b"-Ra"])
         );
         assert_eq!(
             collect_early_args(&["log", "-R", "repo", "", "--traceback", "a"]),
             os_string_vec_from(&[b"-R", b"repo", b"--traceback"])
         );
         assert_eq!(
             collect_early_args(&["log", "--config", "diff.git=1", "-q"]),
             os_string_vec_from(&[b"--config", b"diff.git=1"])
         );
         assert_eq!(
             collect_early_args(&["--cwd=..", "--repository", "r", "log"]),
             os_string_vec_from(&[b"--cwd=..", b"--repository", b"r"])
         );
         assert_eq!(
             collect_early_args(&["log", "--repo=r", "--repos", "a"]),
             os_string_vec_from(&[b"--repo=r"])
         );
     }
 
     #[test]
     fn collect_early_args_orphaned() {
         assert!(collect_early_args(&["log", "-R"]).is_empty());
         assert!(collect_early_args(&["log", "--config"]).is_empty());
     }
 
     #[test]
     fn collect_early_args_unwanted_value() {
         assert!(collect_early_args(&["log", "--traceback="]).is_empty());
     }
 
     fn os_string_vec_from(v: &[&[u8]]) -> Vec<OsString> {
         v.iter().map(|s| OsStr::from_bytes(s).to_owned()).collect()
     }
 }

rust/chg/src/main.rs

@@ -1,103 +1,97 b''
 // 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::{self, 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 umask = unsafe { procutil::get_umask() }; // not thread safe
     let mut loc = Locator::prepare_from_env()?;
     loc.set_early_args(locator::collect_early_args(env::args_os().skip(1)));
     let handler = ChgUiHandler::new();
     let (result_tx, result_rx) = oneshot::channel();
     let fut = loc
         .connect()
         .and_then(|(_, client)| client.attach_io(io::stdin(), io::stdout(), io::stderr()))
         .and_then(move |client| client.set_umask(umask))
         .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",
     )))
 }