sync: add async APIs to oneshot and mpsc (#1211)

Adds:

- oneshot::Sender::close
- mpsc::Receiver::recv
- mpsc::Sender::send

Also renames `poll_next` to `poll_recv`.

Refs: #1210

10 files changed, 143 insertions, 41 deletions

diff --git a/tokio-macros/src/lib.rs b/tokio-macros/src/lib.rs
index 1562b877..c036f552 100644
--- a/tokio-macros/src/lib.rs
+++ b/tokio-macros/src/lib.rs
@@ -67,12 +67,14 @@ pub fn main(args: TokenStream, item: TokenStream) -> TokenStream {
 
     for arg in args {
         match arg {
-            syn::NestedMeta::Meta(syn::Meta::Word(ident)) => match ident.to_string().to_lowercase().as_str() {
-                "multi_thread" => runtime = RuntimeType::Multi,
-                "single_thread" => runtime = RuntimeType::Single,
-                name => panic!("Unknown attribute {} is specified", name),
-            },
-            _ => ()
+            syn::NestedMeta::Meta(syn::Meta::Word(ident)) => {
+                match ident.to_string().to_lowercase().as_str() {
+                    "multi_thread" => runtime = RuntimeType::Multi,
+                    "single_thread" => runtime = RuntimeType::Single,
+                    name => panic!("Unknown attribute {} is specified", name),
+                }
+            }
+            _ => (),
         }
     }
 
@@ -90,7 +92,7 @@ pub fn main(args: TokenStream, item: TokenStream) -> TokenStream {
                 let mut rt = tokio::runtime::current_thread::Runtime::new().unwrap();
                 rt.block_on(async { #body })
             }
-        }
+        },
     };
 
     result.into()
diff --git a/tokio-sync/Cargo.toml b/tokio-sync/Cargo.toml
index aedd4c62..154c6601 100644
--- a/tokio-sync/Cargo.toml
+++ b/tokio-sync/Cargo.toml
@@ -25,14 +25,14 @@ publish = false
 async-traits = ["async-sink", "futures-core-preview"]
 
 [dependencies]
-fnv = "1.0.6"
+async-util = { git = "https://github.com/tokio-rs/async" }
 async-sink = { git = "https://github.com/tokio-rs/async", optional = true }
+fnv = "1.0.6"
 futures-core-preview = { version = "0.3.0-alpha.16", optional = true }
 
 [dev-dependencies]
-async-util = { git = "https://github.com/tokio-rs/async" }
 env_logger = { version = "0.5", default-features = false }
 pin-utils = "0.1.0-alpha.4"
-# tokio = { version = "0.2.0", path = "../tokio" }
+tokio = { version = "*", path = "../tokio" }
 tokio-test = { version = "0.2.0", path = "../tokio-test" }
 loom = { git = "https://github.com/carllerche/loom", branch = "std-future2", features = ["futures"] }
diff --git a/tokio-sync/src/lib.rs b/tokio-sync/src/lib.rs
index 67903ace..384740ac 100644
--- a/tokio-sync/src/lib.rs
+++ b/tokio-sync/src/lib.rs
@@ -7,6 +7,7 @@
 )]
 #![cfg_attr(test, deny(warnings))]
 #![doc(test(no_crate_inject, attr(deny(rust_2018_idioms))))]
+#![feature(async_await)]
 
 //! Asynchronous synchronization primitives.
 //!
diff --git a/tokio-sync/src/mpsc/bounded.rs b/tokio-sync/src/mpsc/bounded.rs
index 67134156..0dc9012f 100644
--- a/tokio-sync/src/mpsc/bounded.rs
+++ b/tokio-sync/src/mpsc/bounded.rs
@@ -132,7 +132,14 @@ impl<T> Receiver<T> {
     }
 
     /// TODO: Dox
-    pub fn poll_next(&mut self, cx: &mut Context<'_>) -> Poll<Option<T>> {
+    pub async fn recv(&mut self) -> Option<T> {
+        use async_util::future::poll_fn;
+
+        poll_fn(|cx| self.poll_recv(cx)).await
+    }
+
+    /// TODO: Dox
+    pub fn poll_recv(&mut self, cx: &mut Context<'_>) -> Poll<Option<T>> {
         self.chan.recv(cx)
     }
 
@@ -150,7 +157,7 @@ impl<T> futures_core::Stream for Receiver<T> {
     type Item = T;
 
     fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<T>> {
-        Receiver::poll_next(self.get_mut(), cx)
+        self.get_mut().poll_recv(cx)
     }
 }
 
@@ -189,6 +196,21 @@ impl<T> Sender<T> {
         self.chan.try_send(message)?;
         Ok(())
     }
+
+    /// Send a value, waiting until there is capacity.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// unimplemented!();
+    /// ```
+    pub async fn send(&mut self, value: T) -> Result<(), SendError> {
+        use async_util::future::poll_fn;
+
+        poll_fn(|cx| self.poll_ready(cx)).await?;
+
+        self.try_send(value).map_err(|_| SendError(()))
+    }
 }
 
 #[cfg(feature = "async-traits")]
diff --git a/tokio-sync/src/mpsc/unbounded.rs b/tokio-sync/src/mpsc/unbounded.rs
index 960bee41..4f7c6b26 100644
--- a/tokio-sync/src/mpsc/unbounded.rs
+++ b/tokio-sync/src/mpsc/unbounded.rs
@@ -88,10 +88,17 @@ impl<T> UnboundedReceiver<T> {
     }
 
     /// TODO: dox
-    pub fn poll_next(&mut self, cx: &mut Context<'_>) -> Poll<Option<T>> {
+    pub fn poll_recv(&mut self, cx: &mut Context<'_>) -> Poll<Option<T>> {
         self.chan.recv(cx)
     }
 
+    /// TODO: Dox
+    pub async fn recv(&mut self) -> Option<T> {
+        use async_util::future::poll_fn;
+
+        poll_fn(|cx| self.poll_recv(cx)).await
+    }
+
     /// Closes the receiving half of a channel, without dropping it.
     ///
     /// This prevents any further messages from being sent on the channel while
diff --git a/tokio-sync/src/oneshot.rs b/tokio-sync/src/oneshot.rs
index c38bb0ce..8e01b3f0 100644
--- a/tokio-sync/src/oneshot.rs
+++ b/tokio-sync/src/oneshot.rs
@@ -217,6 +217,25 @@ impl<T> Sender<T> {
         Pending
     }
 
+    /// Wait for the associated [`Receiver`] handle to drop.
+    ///
+    /// # Return
+    ///
+    /// Returns a `Future` which must be awaited on.
+    ///
+    /// [`Receiver`]: struct.Receiver.html
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// unimplemented!();
+    /// ```
+    pub async fn closed(&mut self) {
+        use async_util::future::poll_fn;
+
+        poll_fn(|cx| self.poll_close(cx)).await
+    }
+
     /// Check if the associated [`Receiver`] handle has been dropped.
     ///
     /// Unlike [`poll_close`], this function does not register a task for
diff --git a/tokio-sync/tests/fuzz_mpsc.rs b/tokio-sync/tests/fuzz_mpsc.rs
index 4a0b6441..57074ea8 100644
--- a/tokio-sync/tests/fuzz_mpsc.rs
+++ b/tokio-sync/tests/fuzz_mpsc.rs
@@ -1,4 +1,5 @@
 #![deny(warnings, rust_2018_idioms)]
+#![feature(async_await)]
 
 #[macro_use]
 extern crate loom;
@@ -32,10 +33,10 @@ fn closing_tx() {
             drop(tx);
         });
 
-        let v = block_on(poll_fn(|cx| rx.poll_next(cx)));
+        let v = block_on(poll_fn(|cx| rx.poll_recv(cx)));
         assert!(v.is_some());
 
-        let v = block_on(poll_fn(|cx| rx.poll_next(cx)));
+        let v = block_on(poll_fn(|cx| rx.poll_recv(cx)));
         assert!(v.is_none());
     });
 }
diff --git a/tokio-sync/tests/fuzz_oneshot.rs b/tokio-sync/tests/fuzz_oneshot.rs
index 9e0a1c40..1872efe0 100644
--- a/tokio-sync/tests/fuzz_oneshot.rs
+++ b/tokio-sync/tests/fuzz_oneshot.rs
@@ -1,4 +1,5 @@
 #![deny(warnings, rust_2018_idioms)]
+#![feature(async_await)]
 
 /// Unwrap a ready value or propagate `Async::Pending`.
 #[macro_export]
diff --git a/tokio-sync/tests/mpsc.rs b/tokio-sync/tests/mpsc.rs
index 17dd3e64..e6b61854 100644
--- a/tokio-sync/tests/mpsc.rs
+++ b/tokio-sync/tests/mpsc.rs
@@ -1,4 +1,5 @@
 #![deny(warnings, rust_2018_idioms)]
+#![feature(async_await)]
 
 use tokio_sync::mpsc;
 use tokio_test::task::MockTask;
@@ -28,16 +29,30 @@ fn send_recv_with_buffer() {
 
     drop(tx);
 
-    let val = assert_ready!(t2.enter(|cx| rx.poll_next(cx)));
+    let val = assert_ready!(t2.enter(|cx| rx.poll_recv(cx)));
     assert_eq!(val, Some(1));
 
-    let val = assert_ready!(t2.enter(|cx| rx.poll_next(cx)));
+    let val = assert_ready!(t2.enter(|cx| rx.poll_recv(cx)));
     assert_eq!(val, Some(2));
 
-    let val = assert_ready!(t2.enter(|cx| rx.poll_next(cx)));
+    let val = assert_ready!(t2.enter(|cx| rx.poll_recv(cx)));
     assert!(val.is_none());
 }
 
+#[tokio::test]
+async fn async_send_recv_with_buffer() {
+    let (mut tx, mut rx) = mpsc::channel(16);
+
+    tokio::spawn(async move {
+        assert_ok!(tx.send(1).await);
+        assert_ok!(tx.send(2).await);
+    });
+
+    assert_eq!(Some(1), rx.recv().await);
+    assert_eq!(Some(2), rx.recv().await);
+    assert_eq!(None, rx.recv().await);
+}
+
 #[test]
 #[cfg(feature = "async-traits")]
 fn send_sink_recv_with_buffer() {
@@ -65,13 +80,13 @@ fn send_sink_recv_with_buffer() {
     t1.enter(|cx| {
         pin_mut!(rx);
 
-        let val = assert_ready!(Stream::poll_next(rx.as_mut(), cx));
+        let val = assert_ready!(rx.as_mut().poll_next(cx));
         assert_eq!(val, Some(1));
 
-        let val = assert_ready!(Stream::poll_next(rx.as_mut(), cx));
+        let val = assert_ready!(rx.as_mut().poll_next(cx));
         assert_eq!(val, Some(2));
 
-        let val = assert_ready!(Stream::poll_next(rx.as_mut(), cx));
+        let val = assert_ready!(rx.as_mut().poll_next(cx));
         assert!(val.is_none());
     });
 }
@@ -97,7 +112,7 @@ fn start_send_past_cap() {
 
     drop(tx1);
 
-    let val = t3.enter(|cx| assert_ready!(rx.poll_next(cx)));
+    let val = t3.enter(|cx| assert_ready!(rx.poll_recv(cx)));
     assert!(val.is_some());
 
     assert!(t2.is_woken());
@@ -105,7 +120,7 @@ fn start_send_past_cap() {
 
     drop(tx2);
 
-    let val = t3.enter(|cx| assert_ready!(rx.poll_next(cx)));
+    let val = t3.enter(|cx| assert_ready!(rx.poll_recv(cx)));
     assert!(val.is_none());
 }
 
@@ -125,18 +140,32 @@ fn send_recv_unbounded() {
     assert_ok!(tx.try_send(1));
     assert_ok!(tx.try_send(2));
 
-    let val = assert_ready!(t1.enter(|cx| rx.poll_next(cx)));
+    let val = assert_ready!(t1.enter(|cx| rx.poll_recv(cx)));
     assert_eq!(val, Some(1));
 
-    let val = assert_ready!(t1.enter(|cx| rx.poll_next(cx)));
+    let val = assert_ready!(t1.enter(|cx| rx.poll_recv(cx)));
     assert_eq!(val, Some(2));
 
     drop(tx);
 
-    let val = assert_ready!(t1.enter(|cx| rx.poll_next(cx)));
+    let val = assert_ready!(t1.enter(|cx| rx.poll_recv(cx)));
     assert!(val.is_none());
 }
 
+#[tokio::test]
+async fn async_send_recv_unbounded() {
+    let (mut tx, mut rx) = mpsc::unbounded_channel();
+
+    tokio::spawn(async move {
+        assert_ok!(tx.try_send(1));
+        assert_ok!(tx.try_send(2));
+    });
+
+    assert_eq!(Some(1), rx.recv().await);
+    assert_eq!(Some(2), rx.recv().await);
+    assert_eq!(None, rx.recv().await);
+}
+
 #[test]
 #[cfg(feature = "async-traits")]
 fn sink_send_recv_unbounded() {
@@ -164,13 +193,13 @@ fn sink_send_recv_unbounded() {
     t1.enter(|cx| {
         pin_mut!(rx);
 
-        let val = assert_ready!(Stream::poll_next(rx.as_mut(), cx));
+        let val = assert_ready!(rx.as_mut().poll_next(cx));
         assert_eq!(val, Some(1));
 
-        let val = assert_ready!(Stream::poll_next(rx.as_mut(), cx));
+        let val = assert_ready!(rx.as_mut().poll_next(cx));
         assert_eq!(val, Some(2));
 
-        let val = assert_ready!(Stream::poll_next(rx.as_mut(), cx));
+        let val = assert_ready!(rx.as_mut().poll_next(cx));
         assert!(val.is_none());
     });
 }
@@ -189,7 +218,7 @@ fn no_t_bounds_buffer() {
     // and sender should be Clone even though T isn't Clone
     assert!(tx.clone().try_send(NoImpls).is_ok());
 
-    let val = assert_ready!(t1.enter(|cx| rx.poll_next(cx)));
+    let val = assert_ready!(t1.enter(|cx| rx.poll_recv(cx)));
     assert!(val.is_some());
 }
 
@@ -207,7 +236,7 @@ fn no_t_bounds_unbounded() {
     // and sender should be Clone even though T isn't Clone
     assert!(tx.clone().try_send(NoImpls).is_ok());
 
-    let val = assert_ready!(t1.enter(|cx| rx.poll_next(cx)));
+    let val = assert_ready!(t1.enter(|cx| rx.poll_recv(cx)));
     assert!(val.is_some());
 }
 
@@ -234,7 +263,7 @@ fn send_recv_buffer_limited() {
 
     t2.enter(|cx| {
         // Take the value
-        let val = assert_ready!(rx.poll_next(cx));
+        let val = assert_ready!(rx.poll_recv(cx));
         assert_eq!(Some(1), val);
     });
 
@@ -251,7 +280,7 @@ fn send_recv_buffer_limited() {
 
     t2.enter(|cx| {
         // Take the value
-        let val = assert_ready!(rx.poll_next(cx));
+        let val = assert_ready!(rx.poll_recv(cx));
         assert_eq!(Some(2), val);
     });
 
@@ -269,7 +298,7 @@ fn recv_close_gets_none_idle() {
     rx.close();
 
     t1.enter(|cx| {
-        let val = assert_ready!(rx.poll_next(cx));
+        let val = assert_ready!(rx.poll_recv(cx));
         assert!(val.is_none());
         assert_ready_err!(tx.poll_ready(cx));
     });
@@ -298,7 +327,7 @@ fn recv_close_gets_none_reserved() {
         assert_ready_err!(tx2.poll_ready(cx));
     });
 
-    t3.enter(|cx| assert_pending!(rx.poll_next(cx)));
+    t3.enter(|cx| assert_pending!(rx.poll_recv(cx)));
 
     assert!(!t1.is_woken());
     assert!(!t2.is_woken());
@@ -308,10 +337,10 @@ fn recv_close_gets_none_reserved() {
     assert!(t3.is_woken());
 
     t3.enter(|cx| {
-        let v = assert_ready!(rx.poll_next(cx));
+        let v = assert_ready!(rx.poll_recv(cx));
         assert_eq!(v, Some(123));
 
-        let v = assert_ready!(rx.poll_next(cx));
+        let v = assert_ready!(rx.poll_recv(cx));
         assert!(v.is_none());
     });
 }
@@ -324,7 +353,7 @@ fn tx_close_gets_none() {
 
     // Run on a task context
     t1.enter(|cx| {
-        let v = assert_ready!(rx.poll_next(cx));
+        let v = assert_ready!(rx.poll_recv(cx));
         assert!(v.is_none());
     });
 }
@@ -341,16 +370,16 @@ fn try_send_fail() {
     let err = assert_err!(tx.try_send("fail"));
     assert!(err.is_full());
 
-    let val = assert_ready!(t1.enter(|cx| rx.poll_next(cx)));
+    let val = assert_ready!(t1.enter(|cx| rx.poll_recv(cx)));
     assert_eq!(val, Some("hello"));
 
     assert_ok!(tx.try_send("goodbye"));
     drop(tx);
 
-    let val = assert_ready!(t1.enter(|cx| rx.poll_next(cx)));
+    let val = assert_ready!(t1.enter(|cx| rx.poll_recv(cx)));
     assert_eq!(val, Some("goodbye"));
 
-    let val = assert_ready!(t1.enter(|cx| rx.poll_next(cx)));
+    let val = assert_ready!(t1.enter(|cx| rx.poll_recv(cx)));
     assert!(val.is_none());
 }
 
diff --git a/tokio-sync/tests/oneshot.rs b/tokio-sync/tests/oneshot.rs
index fc78bd2e..d19fe977 100644
--- a/tokio-sync/tests/oneshot.rs
+++ b/tokio-sync/tests/oneshot.rs
@@ -1,4 +1,5 @@
 #![deny(warnings, rust_2018_idioms)]
+#![feature(async_await)]
 
 use tokio_sync::oneshot;
 use tokio_test::task::MockTask;
@@ -23,6 +24,14 @@ fn send_recv() {
     assert_eq!(val, 1);
 }
 
+#[tokio::test]
+async fn async_send_recv() {
+    let (tx, rx) = oneshot::channel();
+
+    assert_ok!(tx.send(1));
+    assert_eq!(1, assert_ok!(rx.await));
+}
+
 #[test]
 fn close_tx() {
     let (tx, mut rx) = oneshot::channel::<i32>();
@@ -60,6 +69,17 @@ fn close_rx() {
     assert_err!(tx.send(1));
 }
 
+#[tokio::test]
+async fn async_rx_closed() {
+    let (mut tx, rx) = oneshot::channel::<()>();
+
+    tokio::spawn(async move {
+        drop(rx);
+    });
+
+    tx.closed().await;
+}
+
 #[test]
 fn explicit_close_poll() {
     // First, with message sent