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// Copyright (C) 2022 Leandro Lisboa Penz <lpenz@lpenz.org>
// This file is subject to the terms and conditions defined in
// file 'LICENSE', which is part of this source code package.
#![deny(future_incompatible)]
#![deny(nonstandard_style)]
#![deny(missing_docs)]
#![deny(rustdoc::broken_intra_doc_links)]
//! tokio-process-stream is a simple crate that wraps a [`tokio::process`] into a
//! [`tokio::stream`]
//!
//! Having a stream interface to processes is useful when we have multiple sources of data that
//! we want to merge and start processing from a single entry point.
//!
//! This crate provides a [`futures::stream::Stream`] wrapper for [`tokio::process::Child`]. The
//! main struct is [`ProcessLineStream`], which implements the trait, yielding one [`Item`] enum
//! at a time, each containing one line from either stdout ([`Item::Stdout`]) or stderr
//! ([`Item::Stderr`]) of the underlying process until it exits. At this point, the stream
//! yields a single [`Item::Done`] and finishes.
//!
//! Example usage:
//!
//! ```rust
//! use tokio_process_stream::ProcessLineStream;
//! use tokio::process::Command;
//! use tokio_stream::StreamExt;
//! use std::error::Error;
//!
//! #[tokio::main]
//! async fn main() -> Result<(), Box<dyn Error>> {
//! let mut sleep_cmd = Command::new("sleep");
//! sleep_cmd.args(&["1"]);
//! let ls_cmd = Command::new("ls");
//!
//! let sleep_procstream = ProcessLineStream::try_from(sleep_cmd)?;
//! let ls_procstream = ProcessLineStream::try_from(ls_cmd)?;
//! let mut procstream = sleep_procstream.merge(ls_procstream);
//!
//! while let Some(item) = procstream.next().await {
//! println!("{:?}", item);
//! }
//!
//! Ok(())
//! }
//! ```
//!
//! # Streaming chunks
//!
//! It is also possible to stream `Item<Bytes>` chunks with [`ProcessChunkStream`].
//!
//! ```rust
//! use tokio_process_stream::{Item, ProcessChunkStream};
//! use tokio::process::Command;
//! use tokio_stream::StreamExt;
//! use std::error::Error;
//!
//! #[tokio::main]
//! async fn main() -> Result<(), Box<dyn Error>> {
//! let mut procstream: ProcessChunkStream = Command::new("/bin/sh")
//! .arg("-c")
//! .arg(r#"printf "1/2"; sleep 0.1; printf "\r2/2 done\n""#)
//! .try_into()?;
//!
//! while let Some(item) = procstream.next().await {
//! println!("{:?}", item);
//! }
//! Ok(())
//! }
//! ```
use pin_project_lite::pin_project;
use std::{
fmt,
future::Future,
io,
pin::Pin,
process::{ExitStatus, Stdio},
task::{Context, Poll},
};
use tokio::{
io::{AsyncBufReadExt, BufReader},
process::{Child, ChildStderr, ChildStdout, Command},
};
use tokio_stream::{wrappers::LinesStream, Stream};
use tokio_util::io::ReaderStream;
/// [`ProcessStream`] output.
#[derive(Debug)]
pub enum Item<Out> {
/// A stdout chunk printed by the process.
Stdout(Out),
/// A stderr chunk printed by the process.
Stderr(Out),
/// The [`ExitStatus`](std::process::ExitStatus), yielded after the process exits.
Done(io::Result<ExitStatus>),
}
impl<T> Item<T>
where
T: std::ops::Deref,
{
/// Returns a [`Item::Stdout`] dereference, otherwise `None`.
pub fn stdout(&self) -> Option<&T::Target> {
match self {
Self::Stdout(s) => Some(s),
_ => None,
}
}
/// Returns a [`Item::Stderr`] dereference, otherwise `None`.
pub fn stderr(&self) -> Option<&T::Target> {
match self {
Self::Stderr(s) => Some(s),
_ => None,
}
}
}
impl<Out: fmt::Display> fmt::Display for Item<Out> {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
match self {
Item::Stdout(s) => fmt::Display::fmt(&s, f),
Item::Stderr(s) => fmt::Display::fmt(&s, f),
_ => Ok(()),
}
}
}
pin_project! {
/// The main tokio-process-stream struct, which implements the
/// [`Stream`](tokio_stream::Stream) trait
#[derive(Debug)]
pub struct ChildStream<Sout, Serr> {
child: Option<Child>,
stdout: Option<Sout>,
stderr: Option<Serr>,
}
}
impl<Sout, Serr> ChildStream<Sout, Serr> {
/// Return a reference to the child object
pub fn child(&self) -> Option<&Child> {
self.child.as_ref()
}
/// Return a mutable reference to the child object
pub fn child_mut(&mut self) -> Option<&mut Child> {
self.child.as_mut()
}
}
impl<Sout, Serr> TryFrom<Command> for ChildStream<Sout, Serr>
where
ChildStream<Sout, Serr>: From<Child>,
{
type Error = io::Error;
fn try_from(mut command: Command) -> io::Result<Self> {
Self::try_from(&mut command)
}
}
impl<Sout, Serr> TryFrom<&mut Command> for ChildStream<Sout, Serr>
where
ChildStream<Sout, Serr>: From<Child>,
{
type Error = io::Error;
fn try_from(command: &mut Command) -> io::Result<Self> {
Ok(command
.stdout(Stdio::piped())
.stderr(Stdio::piped())
.spawn()?
.into())
}
}
impl<T, Sout, Serr> Stream for ChildStream<Sout, Serr>
where
Sout: Stream<Item = io::Result<T>> + std::marker::Unpin,
Serr: Stream<Item = io::Result<T>> + std::marker::Unpin,
{
type Item = Item<T>;
fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
if self.child.is_none() {
// Keep returning None after we are done and everything is dropped
return Poll::Ready(None);
}
let this = self.project();
if let Some(stderr) = this.stderr {
match Pin::new(stderr).poll_next(cx) {
Poll::Ready(Some(line)) => {
return Poll::Ready(Some(Item::Stderr(line.unwrap())));
}
Poll::Ready(None) => {
*this.stderr = None;
}
Poll::Pending => {}
}
}
if let Some(stdout) = this.stdout {
match Pin::new(stdout).poll_next(cx) {
Poll::Ready(Some(line)) => {
return Poll::Ready(Some(Item::Stdout(line.unwrap())));
}
Poll::Ready(None) => {
*this.stdout = None;
}
Poll::Pending => {}
}
}
if this.stdout.is_none() && this.stderr.is_none() {
// Streams closed, all that is left is waiting for the child to exit:
if let Some(mut child) = std::mem::take(&mut *this.child) {
if let Poll::Ready(sts) = Pin::new(&mut Box::pin(child.wait())).poll(cx) {
return Poll::Ready(Some(Item::Done(sts)));
}
// Sometimes the process can close stdout+stderr before it's ready to be
// 'wait'ed. To handle that, we put child back in this:
*this.child = Some(child);
}
}
Poll::Pending
}
}
/// [`ChildStream`] that produces lines.
pub type ProcessLineStream =
ChildStream<LinesStream<BufReader<ChildStdout>>, LinesStream<BufReader<ChildStderr>>>;
/// Alias for [`ProcessLineStream`].
pub type ProcessStream = ProcessLineStream;
impl From<Child> for ProcessLineStream {
fn from(mut child: Child) -> Self {
let stdout = child
.stdout
.take()
.map(|s| LinesStream::new(BufReader::new(s).lines()));
let stderr = child
.stderr
.take()
.map(|s| LinesStream::new(BufReader::new(s).lines()));
Self {
child: Some(child),
stdout,
stderr,
}
}
}
/// [`ChildStream`] that produces chunks that may part of a line or multiple lines.
///
/// # Example
/// ```
/// use tokio_process_stream::{Item, ProcessChunkStream};
/// use tokio::process::Command;
/// use tokio_stream::StreamExt;
///
/// # #[tokio::main]
/// # async fn main() -> Result<(), Box<dyn std::error::Error>> {
/// // Example of a process that prints onto a single line using '\r'.
/// let mut procstream: ProcessChunkStream = Command::new("/bin/sh")
/// .arg("-c")
/// .arg(r#"printf "1/2"; sleep 0.1; printf "\r2/2 done\n""#)
/// .try_into()?;
///
/// assert_eq!(
/// procstream.next().await.as_ref().and_then(|n| n.stdout()),
/// Some(b"1/2" as _)
/// );
/// assert_eq!(
/// procstream.next().await.as_ref().and_then(|n| n.stdout()),
/// Some(b"\r2/2 done\n" as _)
/// );
/// assert!(matches!(procstream.next().await, Some(Item::Done(_))));
/// # Ok(()) }
/// ```
pub type ProcessChunkStream =
ChildStream<ReaderStream<BufReader<ChildStdout>>, ReaderStream<BufReader<ChildStderr>>>;
impl From<Child> for ProcessChunkStream {
fn from(mut child: Child) -> Self {
let stdout = child
.stdout
.take()
.map(|s| ReaderStream::new(BufReader::new(s)));
let stderr = child
.stderr
.take()
.map(|s| ReaderStream::new(BufReader::new(s)));
Self {
child: Some(child),
stdout,
stderr,
}
}
}