Switch RPCs to stable futures (#3287)

substrate/core/rpc/src/helpers.rs

@@ -14,11 +14,12 @@
 // You should have received a copy of the GNU General Public License
 // along with Substrate.  If not, see <http://www.gnu.org/licenses/>.
 
-use futures::{prelude::*, sync::oneshot};
+use futures::prelude::*;
+use futures03::{channel::oneshot, compat::Compat};
 
 /// Wraps around `oneshot::Receiver` and adjusts the error type to produce an internal error if the
 /// sender gets dropped.
-pub struct Receiver<T>(pub oneshot::Receiver<T>);
+pub struct Receiver<T>(pub Compat<oneshot::Receiver<T>>);
 
 impl<T> Future for Receiver<T> {
 	type Item = T;

substrate/core/rpc/src/system/mod.rs

@@ -23,7 +23,7 @@ pub mod helpers;
 mod tests;
 
 use crate::helpers::Receiver;
-use futures::sync::{mpsc, oneshot};
+use futures03::{channel::{mpsc, oneshot}, compat::Compat};
 use jsonrpc_derive::rpc;
 use network;
 use sr_primitives::traits::{self, Header as HeaderT};
@@ -124,18 +124,18 @@ impl<B: traits::Block> SystemApi<B::Hash, <B::Header as HeaderT>::Number> for Sy
 	fn system_health(&self) -> Receiver<Health> {
 		let (tx, rx) = oneshot::channel();
 		let _ = self.send_back.unbounded_send(Request::Health(tx));
-		Receiver(rx)
+		Receiver(Compat::new(rx))
 	}
 
 	fn system_peers(&self) -> Receiver<Vec<PeerInfo<B::Hash, <B::Header as HeaderT>::Number>>> {
 		let (tx, rx) = oneshot::channel();
 		let _ = self.send_back.unbounded_send(Request::Peers(tx));
-		Receiver(rx)
+		Receiver(Compat::new(rx))
 	}
 
 	fn system_network_state(&self) -> Receiver<network::NetworkState> {
 		let (tx, rx) = oneshot::channel();
 		let _ = self.send_back.unbounded_send(Request::NetworkState(tx));
-		Receiver(rx)
+		Receiver(Compat::new(rx))
 	}
 }

substrate/core/rpc/src/system/tests.rs

@@ -20,7 +20,7 @@ use network::{self, PeerId};
 use network::config::Roles;
 use test_client::runtime::Block;
 use assert_matches::assert_matches;
-use futures::{prelude::*, sync::mpsc};
+use futures03::{prelude::*, channel::mpsc};
 use std::thread;
 
 struct Status {
@@ -46,7 +46,7 @@ fn api<T: Into<Option<Status>>>(sync: T) -> System<Block> {
 	let should_have_peers = !status.is_dev;
 	let (tx, rx) = mpsc::unbounded();
 	thread::spawn(move || {
-		tokio::run(rx.for_each(move |request| {
+		futures03::executor::block_on(rx.for_each(move |request| {
 			match request {
 				Request::Health(sender) => {
 					let _ = sender.send(Health {
@@ -82,7 +82,7 @@ fn api<T: Into<Option<Status>>>(sync: T) -> System<Block> {
 				}
 			};
 
-			Ok(())
+			future::ready(())
 		}))
 	});
 	System::new(SystemInfo {