add an unstable task::blocking function

src/fs/read_dir.rs

@@ -5,7 +5,7 @@ use crate::fs::DirEntry;
 use crate::future::Future;
 use crate::io;
 use crate::stream::Stream;
-use crate::task::{blocking, Context, Poll};
+use crate::task::{blocking, Context, JoinHandle, Poll};
 
 /// Returns a stream of entries in a directory.
 ///
@@ -71,7 +71,7 @@ pub struct ReadDir(State);
 #[derive(Debug)]
 enum State {
     Idle(Option<std::fs::ReadDir>),
-    Busy(blocking::JoinHandle<(std::fs::ReadDir, Option<io::Result<std::fs::DirEntry>>)>),
+    Busy(JoinHandle<(std::fs::ReadDir, Option<io::Result<std::fs::DirEntry>>)>),
 }
 
 impl ReadDir {

src/io/stderr.rs

@@ -5,7 +5,7 @@ use cfg_if::cfg_if;
 
 use crate::future::Future;
 use crate::io::{self, Write};
-use crate::task::{blocking, Context, Poll};
+use crate::task::{blocking, Context, JoinHandle, Poll};
 
 /// Constructs a new handle to the standard error of the current process.
 ///
@@ -56,7 +56,7 @@ enum State {
     /// The stderr is blocked on an asynchronous operation.
     ///
     /// Awaiting this operation will result in the new state of the stderr.
-    Busy(blocking::JoinHandle<State>),
+    Busy(JoinHandle<State>),
 }
 
 /// Inner representation of the asynchronous stderr.

src/io/stdin.rs

@@ -5,7 +5,7 @@ use cfg_if::cfg_if;
 
 use crate::future::{self, Future};
 use crate::io::{self, Read};
-use crate::task::{blocking, Context, Poll};
+use crate::task::{blocking, Context, JoinHandle, Poll};
 
 /// Constructs a new handle to the standard input of the current process.
 ///
@@ -57,7 +57,7 @@ enum State {
     /// The stdin is blocked on an asynchronous operation.
     ///
     /// Awaiting this operation will result in the new state of the stdin.
-    Busy(blocking::JoinHandle<State>),
+    Busy(JoinHandle<State>),
 }
 
 /// Inner representation of the asynchronous stdin.

src/io/stdout.rs

@@ -5,7 +5,7 @@ use cfg_if::cfg_if;
 
 use crate::future::Future;
 use crate::io::{self, Write};
-use crate::task::{blocking, Context, Poll};
+use crate::task::{blocking, Context, JoinHandle, Poll};
 
 /// Constructs a new handle to the standard output of the current process.
 ///
@@ -56,7 +56,7 @@ enum State {
     /// The stdout is blocked on an asynchronous operation.
     ///
     /// Awaiting this operation will result in the new state of the stdout.
-    Busy(blocking::JoinHandle<State>),
+    Busy(JoinHandle<State>),
 }
 
 /// Inner representation of the asynchronous stdout.

src/net/addr.rs

@@ -7,8 +7,7 @@ use cfg_if::cfg_if;
 
 use crate::future::Future;
 use crate::io;
-use crate::task::blocking;
-use crate::task::{Context, Poll};
+use crate::task::{blocking, Context, JoinHandle, Poll};
 
 cfg_if! {
     if #[cfg(feature = "docs")] {
@@ -48,7 +47,7 @@ pub trait ToSocketAddrs {
 #[allow(missing_debug_implementations)]
 pub enum ToSocketAddrsFuture<'a, I> {
     Phantom(PhantomData<&'a ()>),
-    Join(blocking::JoinHandle<io::Result<I>>),
+    Join(JoinHandle<io::Result<I>>),
     Ready(Option<io::Result<I>>),
 }
 

src/task/blocking.rs

@@ -1,7 +1,5 @@
 //! A thread pool for running blocking functions asynchronously.
 
-use std::fmt;
-use std::pin::Pin;
 use std::sync::atomic::{AtomicU64, Ordering};
 use std::thread;
 use std::time::Duration;
@@ -10,16 +8,16 @@ use crossbeam_channel::{bounded, Receiver, Sender};
 use lazy_static::lazy_static;
 
 use crate::future::Future;
-use crate::task::{Context, Poll};
+use crate::task::task::{JoinHandle, Tag};
 use crate::utils::abort_on_panic;
 
 const MAX_THREADS: u64 = 10_000;
 
 static DYNAMIC_THREAD_COUNT: AtomicU64 = AtomicU64::new(0);
 
 struct Pool {
-    sender: Sender<async_task::Task<()>>,
-    receiver: Receiver<async_task::Task<()>>,
+    sender: Sender<async_task::Task<Tag>>,
+    receiver: Receiver<async_task::Task<Tag>>,
 }
 
 lazy_static! {
@@ -85,7 +83,7 @@ fn maybe_create_another_blocking_thread() {
 // Enqueues work, attempting to send to the threadpool in a
 // nonblocking way and spinning up another worker thread if
 // there is not a thread ready to accept the work.
-fn schedule(t: async_task::Task<()>) {
+fn schedule(t: async_task::Task<Tag>) {
     if let Err(err) = POOL.sender.try_send(t) {
         // We were not able to send to the channel without
         // blocking. Try to spin up another thread and then
@@ -98,35 +96,15 @@ fn schedule(t: async_task::Task<()>) {
 /// Spawns a blocking task.
 ///
 /// The task will be spawned onto a thread pool specifically dedicated to blocking tasks.
-pub fn spawn<F, R>(future: F) -> JoinHandle<R>
+pub(crate) fn spawn<F, R>(future: F) -> JoinHandle<R>
 where
     F: Future<Output = R> + Send + 'static,
     R: Send + 'static,
 {
-    let (task, handle) = async_task::spawn(future, schedule, ());
+    let tag = Tag::new(None);
+    let (task, handle) = async_task::spawn(future, schedule, tag);
     task.schedule();
-    JoinHandle(handle)
-}
-
-/// A handle to a blocking task.
-pub struct JoinHandle<R>(async_task::JoinHandle<R, ()>);
-
-impl<R> Unpin for JoinHandle<R> {}
-
-impl<R> Future for JoinHandle<R> {
-    type Output = R;
-
-    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
-        Pin::new(&mut self.0).poll(cx).map(|out| out.unwrap())
-    }
-}
-
-impl<R> fmt::Debug for JoinHandle<R> {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        f.debug_struct("JoinHandle")
-            .field("handle", &self.0)
-            .finish()
-    }
+    JoinHandle::new(handle)
 }
 
 /// Generates a random number in `0..n`.

src/task/mod.rs

@@ -48,3 +48,19 @@ mod task_local;
 mod worker;
 
 pub(crate) mod blocking;
+
+/// Spawns a blocking task.
+///
+/// The task will be spawned onto a thread pool specifically dedicated to blocking tasks.
+// Once this function stabilizes we should merge `blocking::spawn` into this so
+// all code in our crate uses `task::blocking` too.
+#[cfg(any(feature = "unstable", feature = "docs"))]
+#[cfg_attr(feature = "docs", doc(cfg(unstable)))]
+#[inline]
+pub fn blocking<F, R>(future: F) -> task::JoinHandle<R>
+where
+    F: crate::future::Future<Output = R> + Send + 'static,
+    R: Send + 'static,
+{
+    blocking::spawn(future)
+}