jobs: don't early exit when there are no jobs (#1621)

* jobs: don't early exit when there are no jobs

* utils: fix merged test

* utils: less verbose

* utils: add an assert subsystem is running

* utils: use TimeoutExt from test-helpers

* test-helpers: use TimeoutExt

polkadot/node/subsystem-util/src/lib.rs

@@ -643,12 +643,17 @@ where
 
 	fn poll_next(self: Pin<&mut Self>, cx: &mut task::Context) -> task::Poll<Option<Self::Item>> {
 		// pin-project the outgoing messages
-		self.project().outgoing_msgs.poll_next(cx).map(|opt| {
+		let result = self.project().outgoing_msgs.poll_next(cx).map(|opt| {
 			opt.and_then(|(stream_yield, _)| match stream_yield {
 				StreamYield::Item(msg) => Some(msg),
 				StreamYield::Finished(_) => None,
 			})
-		})
+		});
+		// we don't want the stream to end if the jobs are empty at some point
+		match result {
+			task::Poll::Ready(None) => task::Poll::Pending,
+			otherwise => otherwise,
+		}
 	}
 }
 
@@ -731,7 +736,7 @@ where
 		loop {
 			select! {
 				incoming = ctx.recv().fuse() => if Self::handle_incoming(incoming, &mut jobs, &run_args, &metrics, &mut err_tx).await { break },
-				outgoing = jobs.next().fuse() => if Self::handle_outgoing(outgoing, &mut ctx, &mut err_tx).await { break },
+				outgoing = jobs.next().fuse() => Self::handle_outgoing(outgoing, &mut ctx, &mut err_tx).await,
 				complete => break,
 			}
 		}
@@ -841,21 +846,16 @@ where
 		false
 	}
 
-	// handle an outgoing message. return true if we should break afterwards.
+	// handle an outgoing message.
 	async fn handle_outgoing(
 		outgoing: Option<Job::FromJob>,
 		ctx: &mut Context,
 		err_tx: &mut Option<mpsc::Sender<(Option<Hash>, JobsError<Job::Error>)>>,
-	) -> bool {
-		match outgoing {
-			Some(msg) => {
-				if let Err(e) = ctx.send_message(msg.into()).await {
-					Self::fwd_err(None, Error::from(e).into(), err_tx).await;
-				}
-			}
-			None => return true,
+	) {
+		let msg = outgoing.expect("the Jobs stream never ends; qed");
+		if let Err(e) = ctx.send_message(msg.into()).await {
+			Self::fwd_err(None, Error::from(e).into(), err_tx).await;
 		}
-		false
 	}
 }
 
@@ -985,11 +985,10 @@ mod tests {
 		channel::mpsc,
 		executor,
 		stream::{self, StreamExt},
-		Future, FutureExt, SinkExt,
+		future, Future, FutureExt, SinkExt,
 	};
-	use futures_timer::Delay;
 	use polkadot_primitives::v1::Hash;
-	use polkadot_node_subsystem_test_helpers::{self as test_helpers, make_subsystem_context};
+	use polkadot_node_subsystem_test_helpers::{self as test_helpers, make_subsystem_context, TimeoutExt as _};
 	use std::{collections::HashMap, convert::TryFrom, pin::Pin, time::Duration};
 
 	// basic usage: in a nutshell, when you want to define a subsystem, just focus on what its jobs do;
@@ -1157,16 +1156,14 @@ mod tests {
 
 		let subsystem = FakeCandidateSelectionSubsystem::run(context, run_args, (), pool, Some(err_tx));
 		let test_future = test(overseer_handle, err_rx);
-		let timeout = Delay::new(Duration::from_secs(2));
 
-		futures::pin_mut!(subsystem, test_future, timeout);
+		futures::pin_mut!(subsystem, test_future);
 
 		executor::block_on(async move {
-			futures::select! {
-				_ = test_future.fuse() => (),
-				_ = subsystem.fuse() => (),
-				_ = timeout.fuse() => panic!("test timed out instead of completing"),
-			}
+			future::join(subsystem, test_future)
+				.timeout(Duration::from_secs(2))
+				.await
+				.expect("test timed out instead of completing")
 		});
 	}
 
@@ -1195,6 +1192,10 @@ mod tests {
 				)))
 				.await;
 
+			overseer_handle
+				.send(FromOverseer::Signal(OverseerSignal::Conclude))
+				.await;
+
 			let errs: Vec<_> = err_rx.collect().await;
 			assert_eq!(errs.len(), 0);
 		});
@@ -1224,12 +1225,23 @@ mod tests {
 
 	#[test]
 	fn sending_to_a_non_running_job_do_not_stop_the_subsystem() {
-		let run_args = HashMap::new();
+		let relay_parent = Hash::repeat_byte(0x01);
+		let mut run_args = HashMap::new();
+		run_args.insert(
+			relay_parent.clone(),
+			vec![FromJob::Test],
+		);
 
 		test_harness(run_args, |mut overseer_handle, err_rx| async move {
+			overseer_handle
+				.send(FromOverseer::Signal(OverseerSignal::ActiveLeaves(
+					ActiveLeavesUpdate::start_work(relay_parent),
+				)))
+				.await;
+
 			// send to a non running job
 			overseer_handle
-				.send(FromOverseer::Communication { 
+				.send(FromOverseer::Communication {
 					msg: Default::default(),
 				})
 				.await;
@@ -1240,6 +1252,10 @@ mod tests {
 				AllMessages::CandidateSelection(_)
 			);
 
+			overseer_handle
+				.send(FromOverseer::Signal(OverseerSignal::Conclude))
+				.await;
+
 			let errs: Vec<_> = err_rx.collect().await;
 			assert_eq!(errs.len(), 0);
 		});