Rewrite with async/await

Cargo.toml

@@ -8,22 +8,36 @@ repository = "https://github.com/paritytech/finality-grandpa"
 edition = "2018"
 
 [dependencies]
-futures = { version = "0.3.1", default-features = false }
+async-trait = "0.1.36"
+async-rwlock = { version = "1.3.0", optional = true }
+futures = { version = "0.3.7", default-features = false, features = [ "async-await" ] }
 futures-timer = { version = "2.0.2", optional = true }
 log = { version = "0.4", optional = true }
-parking_lot = { version = "0.9", optional = true }
 parity-scale-codec = { version = "1.0.3", optional = true, default-features = false, features = ["derive"] }
 num = { package = "num-traits", version = "0.2", default-features = false }
 rand = {version = "0.6.0", optional = true }
 either = { version = "1.5.3", default-features = false }
 
 [dev-dependencies]
+futures = { version = "0.3.7", default-features = false, features = [ "async-await", "thread-pool" ] }
 rand = "0.7.0"
 quickcheck = "0.9"
+parking_lot = "0.9"
+async-std = { version = "1.6.5", features = ["unstable"] }
+env_logger = "0.8"
+
 
 [features]
 default = ["std"]
-std = ["parity-scale-codec/std", "num/std", "parking_lot", "log", "futures-timer", "futures/executor"]
+std = [
+	"parity-scale-codec/std",
+	"num/std",
+	"async-rwlock",
+	"log",
+	"futures-timer",
+	"futures/executor",
+	"futures/async-await",
+]
 derive-codec = ["parity-scale-codec"]
 test-helpers = ["fuzz-helpers", "rand", "std"]
 fuzz-helpers = []

src/bridge_state.rs

@@ -15,22 +15,18 @@
 //! Bridging round state between rounds.
 
 use crate::round::State as RoundState;
-use futures::task;
-use parking_lot::{RwLock, RwLockReadGuard};
+use async_rwlock::{RwLock, RwLockReadGuard};
 use std::sync::Arc;
-use std::task::Context;
 
 // round state bridged across rounds.
 struct Bridged<H, N> {
 	inner: RwLock<RoundState<H, N>>,
-	waker: task::AtomicWaker,
 }
 
 impl<H, N> Bridged<H, N> {
 	fn new(inner: RwLock<RoundState<H, N>>) -> Self {
 		Bridged {
 			inner,
-			waker: task::AtomicWaker::new(),
 		}
 	}
 }
@@ -40,9 +36,8 @@ pub(crate) struct PriorView<H, N>(Arc<Bridged<H, N>>);
 
 impl<H, N> PriorView<H, N> {
 	/// Push an update to the latter view.
-	pub(crate) fn update(&self, new: RoundState<H, N>) {
-		*self.0.inner.write() = new;
-		self.0.waker.wake();
+	pub(crate) async fn update(&self, new: RoundState<H, N>) {
+		*self.0.inner.write().await = new;
 	}
 }
 
@@ -51,9 +46,8 @@ pub(crate) struct LatterView<H, N>(Arc<Bridged<H, N>>);
 
 impl<H, N> LatterView<H, N> {
 	/// Fetch a handle to the last round-state.
-	pub(crate) fn get(&self, cx: &mut Context) -> RwLockReadGuard<RoundState<H, N>> {
-		self.0.waker.register(cx.waker());
-		self.0.inner.read()
+	pub(crate) async fn get(&self) -> RwLockReadGuard<'_, RoundState<H, N>> {
+		self.0.inner.read().await
 	}
 }
 
@@ -73,7 +67,9 @@ pub(crate) fn bridge_state<H, N>(initial: RoundState<H, N>) -> (PriorView<H, N>,
 
 #[cfg(test)]
 mod tests {
-	use std::{sync::Barrier, task::Poll};
+	use async_std::sync::Barrier;
+	use futures::executor::LocalPool;
+	use futures::task::SpawnExt;
 	use super::*;
 
 	#[test]
@@ -85,28 +81,25 @@ mod tests {
 			completable: false,
 		};
 
+		let mut pool = LocalPool::new();
 		let (prior, latter) = bridge_state(initial);
-		let waits_for_finality = ::futures::future::poll_fn(move |cx| -> Poll<()> {
-			if latter.get(cx).finalized.is_some() {
-				Poll::Ready(())
-			} else {
-				Poll::Pending
-			}
-		});
 
 		let barrier = Arc::new(Barrier::new(2));
 		let barrier_other = barrier.clone();
-		::std::thread::spawn(move || {
-			barrier_other.wait();
+
+		pool.spawner().spawn(async move {
+			barrier_other.wait().await;
 			prior.update(RoundState {
 				prevote_ghost: Some(("5", 5)),
 				finalized: Some(("1", 1)),
 				estimate: Some(("3", 3)),
 				completable: true,
-			});
-		});
+			}).await;
+		}).unwrap();
 
-		barrier.wait();
-		futures::executor::block_on(waits_for_finality);
+		pool.run_until(async {
+			barrier.wait().await;
+			while !latter.get().await.finalized.is_some() {}
+		});
 	}
 }

src/lib.rs

@@ -24,6 +24,7 @@
 //!
 //! Equivocation detection and vote-set management is done in the `round` module.
 //! The work for actually casting votes is done in the `voter` module.
+#![recursion_limit="1024"]
 
 #![warn(missing_docs)]
 #![cfg_attr(not(feature = "std"), no_std)]