task: add AbortOnDropHandle type (#6786)

tokio-util/src/task/abort_on_drop.rs

@@ -0,0 +1,63 @@
+//! An [`AbortOnDropHandle`] is like a [`JoinHandle`], except that it
+//! will abort the task as soon as it is dropped.
+
+use tokio::task::{AbortHandle, JoinError, JoinHandle};
+
+use std::{
+    future::Future,
+    pin::Pin,
+    task::{Context, Poll},
+};
+
+/// A wrapper around a [`tokio::task::JoinHandle`],
+/// which [aborts] the task when it is dropped.
+///
+/// [aborts]: tokio::task::JoinHandle::abort
+#[must_use = "Dropping the handle aborts the task immediately"]
+#[derive(Debug)]
+pub struct AbortOnDropHandle<T>(JoinHandle<T>);
+
+impl<T> Drop for AbortOnDropHandle<T> {
+    fn drop(&mut self) {
+        self.0.abort()
+    }
+}
+
+impl<T> AbortOnDropHandle<T> {
+    /// Create an [`AbortOnDropHandle`] from a [`JoinHandle`].
+    pub fn new(handle: JoinHandle<T>) -> Self {
+        Self(handle)
+    }
+
+    /// Abort the task associated with this handle,
+    /// equivalent to [`JoinHandle::abort`].
+    pub fn abort(&self) {
+        self.0.abort()
+    }
+
+    /// Checks if the task associated with this handle is finished,
+    /// equivalent to [`JoinHandle::is_finished`].
+    pub fn is_finished(&self) -> bool {
+        self.0.is_finished()
+    }
+
+    /// Returns a new [`AbortHandle`] that can be used to remotely abort this task,
+    /// equivalent to [`JoinHandle::abort_handle`].
+    pub fn abort_handle(&self) -> AbortHandle {
+        self.0.abort_handle()
+    }
+}
+
+impl<T> Future for AbortOnDropHandle<T> {
+    type Output = Result<T, JoinError>;
+
+    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+        Pin::new(&mut self.0).poll(cx)
+    }
+}
+
+impl<T> AsRef<JoinHandle<T>> for AbortOnDropHandle<T> {
+    fn as_ref(&self) -> &JoinHandle<T> {
+        &self.0
+    }
+}

tokio-util/src/task/mod.rs

@@ -11,3 +11,6 @@ pub use join_map::{JoinMap, JoinMapKeys};
 
 pub mod task_tracker;
 pub use task_tracker::TaskTracker;
+
+mod abort_on_drop;
+pub use abort_on_drop::AbortOnDropHandle;

tokio-util/tests/abort_on_drop.rs

@@ -0,0 +1,27 @@
+use tokio::sync::oneshot;
+use tokio_util::task::AbortOnDropHandle;
+
+#[tokio::test]
+async fn aborts_task_on_drop() {
+    let (mut tx, rx) = oneshot::channel::<bool>();
+    let handle = tokio::spawn(async move {
+        let _ = rx.await;
+    });
+    let handle = AbortOnDropHandle::new(handle);
+    drop(handle);
+    tx.closed().await;
+    assert!(tx.is_closed());
+}
+
+#[tokio::test]
+async fn aborts_task_directly() {
+    let (mut tx, rx) = oneshot::channel::<bool>();
+    let handle = tokio::spawn(async move {
+        let _ = rx.await;
+    });
+    let handle = AbortOnDropHandle::new(handle);
+    handle.abort();
+    tx.closed().await;
+    assert!(tx.is_closed());
+    assert!(handle.is_finished());
+}