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Rollup merge of #97149 - ChrisDenton:win_async_pipes, r=m-ou-se
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Windows: `CommandExt::async_pipes`

Discussed in tokio-rs/tokio#4670 was the need for third party crates to be able to force `process::Command::spawn` to create pipes as async.

This implements the suggestion for a `async_pipes` method that gives third party crates that option.

# Example:

```rust
use std::process::{Command, Stdio};

Command::new("cmd")
    .async_pipes(true)
    .stdin(Stdio::piped())
    .stdout(Stdio::piped())
    .stderr(Stdio::piped())
    .spawn()
    .unwrap();
```
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Dylan-DPC authored Jun 20, 2022
2 parents d99e292 + e819844 commit 1abb227
Showing 1 changed file with 40 additions and 0 deletions.
40 changes: 40 additions & 0 deletions std/src/os/windows/process.rs
Original file line number Diff line number Diff line change
Expand Up @@ -161,6 +161,37 @@ pub trait CommandExt: Sealed {
/// `CommandLineToArgvW` escaping rules.
#[stable(feature = "windows_process_extensions_raw_arg", since = "1.62.0")]
fn raw_arg<S: AsRef<OsStr>>(&mut self, text_to_append_as_is: S) -> &mut process::Command;

/// When [`process::Command`] creates pipes, request that our side is always async.
///
/// By default [`process::Command`] may choose to use pipes where both ends
/// are opened for synchronous read or write operations. By using
/// `async_pipes(true)`, this behavior is overridden so that our side is
/// always async.
///
/// This is important because if doing async I/O a pipe or a file has to be
/// opened for async access.
///
/// The end of the pipe sent to the child process will always be synchronous
/// regardless of this option.
///
/// # Example
///
/// ```
/// #![feature(windows_process_extensions_async_pipes)]
/// use std::os::windows::process::CommandExt;
/// use std::process::{Command, Stdio};
///
/// # let program = "";
///
/// Command::new(program)
/// .async_pipes(true)
/// .stdin(Stdio::piped())
/// .stdout(Stdio::piped())
/// .stderr(Stdio::piped());
/// ```
#[unstable(feature = "windows_process_extensions_async_pipes", issue = "98289")]
fn async_pipes(&mut self, always_async: bool) -> &mut process::Command;
}

#[stable(feature = "windows_process_extensions", since = "1.16.0")]
Expand All @@ -179,6 +210,15 @@ impl CommandExt for process::Command {
self.as_inner_mut().raw_arg(raw_text.as_ref());
self
}

fn async_pipes(&mut self, always_async: bool) -> &mut process::Command {
// FIXME: This currently has an intentional no-op implementation.
// For the time being our side of the pipes will always be async.
// Once the ecosystem has adjusted, we may then be able to start making
// use of synchronous pipes within the standard library.
let _ = always_async;
self
}
}

#[unstable(feature = "windows_process_extensions_main_thread_handle", issue = "96723")]
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