Convert SyncingEngine::run to use tokio::select! instead of polli…

…ng (paritytech#2132)

substrate/client/network/sync/Cargo.toml

@@ -30,6 +30,7 @@ schnellru = "0.2.1"
 smallvec = "1.11.0"
 thiserror = "1.0"
 tokio-stream = "0.1.14"
+tokio = { version = "1.32.0", features = ["time", "macros"] }
 fork-tree = { path = "../../../utils/fork-tree" }
 prometheus-endpoint = { package = "substrate-prometheus-endpoint", path = "../../../utils/prometheus" }
 sc-client-api = { path = "../../api" }

substrate/client/network/sync/src/block_announce_validator.rs

@@ -16,10 +16,11 @@
 // You should have received a copy of the GNU General Public License
 // along with this program. If not, see <https://www.gnu.org/licenses/>.
 
-//! `BlockAnnounceValidator` is responsible for async validation of block announcements.
+//! [`BlockAnnounceValidator`] is responsible for async validation of block announcements.
+//! [`Stream`] implemented by [`BlockAnnounceValidator`] never terminates.
 
 use crate::futures_stream::FuturesStream;
-use futures::{Future, FutureExt, Stream, StreamExt};
+use futures::{stream::FusedStream, Future, FutureExt, Stream, StreamExt};
 use libp2p::PeerId;
 use log::{debug, error, trace, warn};
 use sc_network_common::sync::message::BlockAnnounce;
@@ -300,6 +301,13 @@ impl<B: BlockT> Stream for BlockAnnounceValidator<B> {
 	}
 }
 
+// As [`BlockAnnounceValidator`] never terminates, we can easily implement [`FusedStream`] for it.
+impl<B: BlockT> FusedStream for BlockAnnounceValidator<B> {
+	fn is_terminated(&self) -> bool {
+		false
+	}
+}
+
 #[cfg(test)]
 mod tests {
 	use super::*;