From f957f7f9a7363db3a2640b55354c38958acc9c79 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?F=C3=A9lix=20Saparelli?= <felix@passcod.name>
Date: Thu, 29 Jul 2021 03:42:03 +1200
Subject: [PATCH] process: add Child::raw_handle() on windows (#3998)

Fixes #3987
---
 tokio/src/process/mod.rs          | 12 ++++++++++++
 tokio/src/process/windows.rs      |  8 +++++++-
 tokio/tests/process_raw_handle.rs | 23 +++++++++++++++++++++++
 3 files changed, 42 insertions(+), 1 deletion(-)
 create mode 100644 tokio/tests/process_raw_handle.rs

diff --git a/tokio/src/process/mod.rs b/tokio/src/process/mod.rs
index 7ae503f51..42654b198 100644
--- a/tokio/src/process/mod.rs
+++ b/tokio/src/process/mod.rs
@@ -199,6 +199,8 @@ use std::io;
 #[cfg(unix)]
 use std::os::unix::process::CommandExt;
 #[cfg(windows)]
+use std::os::windows::io::{AsRawHandle, RawHandle};
+#[cfg(windows)]
 use std::os::windows::process::CommandExt;
 use std::path::Path;
 use std::pin::Pin;
@@ -952,6 +954,16 @@ impl Child {
         }
     }
 
+    /// Extracts the raw handle of the process associated with this child while
+    /// it is still running. Returns `None` if the child has exited.
+    #[cfg(windows)]
+    pub fn raw_handle(&self) -> Option<RawHandle> {
+        match &self.child {
+            FusedChild::Child(c) => Some(c.inner.as_raw_handle()),
+            FusedChild::Done(_) => None,
+        }
+    }
+
     /// Attempts to force the child to exit, but does not wait for the request
     /// to take effect.
     ///
diff --git a/tokio/src/process/windows.rs b/tokio/src/process/windows.rs
index 7237525da..06fc1b6cf 100644
--- a/tokio/src/process/windows.rs
+++ b/tokio/src/process/windows.rs
@@ -24,7 +24,7 @@ use mio::windows::NamedPipe;
 use std::fmt;
 use std::future::Future;
 use std::io;
-use std::os::windows::prelude::{AsRawHandle, FromRawHandle, IntoRawHandle};
+use std::os::windows::prelude::{AsRawHandle, FromRawHandle, IntoRawHandle, RawHandle};
 use std::pin::Pin;
 use std::process::Stdio;
 use std::process::{Child as StdChild, Command as StdCommand, ExitStatus};
@@ -144,6 +144,12 @@ impl Future for Child {
     }
 }
 
+impl AsRawHandle for Child {
+    fn as_raw_handle(&self) -> RawHandle {
+        self.child.as_raw_handle()
+    }
+}
+
 impl Drop for Waiting {
     fn drop(&mut self) {
         unsafe {
diff --git a/tokio/tests/process_raw_handle.rs b/tokio/tests/process_raw_handle.rs
new file mode 100644
index 000000000..727e66d65
--- /dev/null
+++ b/tokio/tests/process_raw_handle.rs
@@ -0,0 +1,23 @@
+#![warn(rust_2018_idioms)]
+#![cfg(feature = "full")]
+#![cfg(windows)]
+
+use tokio::process::Command;
+use winapi::um::processthreadsapi::GetProcessId;
+
+#[tokio::test]
+async fn obtain_raw_handle() {
+    let mut cmd = Command::new("cmd");
+    cmd.kill_on_drop(true);
+    cmd.arg("/c");
+    cmd.arg("pause");
+
+    let child = cmd.spawn().unwrap();
+
+    let orig_id = child.id().expect("missing id");
+    assert!(orig_id > 0);
+
+    let handle = child.raw_handle().expect("process stopped");
+    let handled_id = unsafe { GetProcessId(handle as _) };
+    assert_eq!(handled_id, orig_id);
+}