Make <SubstreamRef as AsyncWrite>::shutdown imply flush (#1180)

* Make `<SubstreamRef as AsyncWrite>::shutdown` imply flush

* Use try_ready

* Apply suggestions from code review

Co-Authored-By: Toralf Wittner <tw@dtex.org>

core/src/muxing.rs

@@ -338,6 +338,7 @@ where
     SubstreamRef {
         muxer,
         substream: Some(substream),
+        shutdown_state: ShutdownState::Shutdown,
     }
 }
 
@@ -349,6 +350,13 @@ where
 {
     muxer: P,
     substream: Option<<P::Target as StreamMuxer>::Substream>,
+    shutdown_state: ShutdownState,
+}
+
+enum ShutdownState {
+    Shutdown,
+    Flush,
+    Done,
 }
 
 impl<P> fmt::Debug for SubstreamRef<P>
@@ -431,8 +439,21 @@ where
     #[inline]
     fn shutdown(&mut self) -> Poll<(), io::Error> {
         let s = self.substream.as_mut().expect("substream was empty");
-        self.muxer.shutdown_substream(s).map_err(|e| e.into())?;
-        Ok(Async::Ready(()))
+        loop {
+            match self.shutdown_state {
+                ShutdownState::Shutdown => {
+                    try_ready!(self.muxer.shutdown_substream(s).map_err(|e| e.into()));
+                    self.shutdown_state = ShutdownState::Flush;
+                }
+                ShutdownState::Flush => {
+                    try_ready!(self.muxer.flush_substream(s).map_err(|e| e.into()));
+                    self.shutdown_state = ShutdownState::Done;
+                }
+                ShutdownState::Done => {
+                    return Ok(Async::Ready(()));
+                }
+            }
+        }
     }
 
     #[inline]

muxers/mplex/tests/async_write.rs

@@ -0,0 +1,86 @@
+// Copyright 2019 Parity Technologies (UK) Ltd.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a
+// copy of this software and associated documentation files (the "Software"),
+// to deal in the Software without restriction, including without limitation
+// the rights to use, copy, modify, merge, publish, distribute, sublicense,
+// and/or sell copies of the Software, and to permit persons to whom the
+// Software is furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+use libp2p_core::{muxing, Transport, transport::ListenerEvent};
+use libp2p_tcp::TcpConfig;
+use futures::prelude::*;
+use std::sync::{Arc, mpsc};
+use std::thread;
+use tokio::runtime::current_thread::Runtime;
+
+#[test]
+fn async_write() {
+    // Tests that `AsyncWrite::shutdown` implies flush.
+
+    let (tx, rx) = mpsc::channel();
+
+    let bg_thread = thread::spawn(move || {
+        let transport =
+            TcpConfig::new().with_upgrade(libp2p_mplex::MplexConfig::new());
+
+        let mut listener = transport
+            .listen_on("/ip4/127.0.0.1/tcp/0".parse().unwrap())
+            .unwrap();
+
+        let addr = listener.by_ref().wait()
+            .next()
+            .expect("some event")
+            .expect("no error")
+            .into_new_address()
+            .expect("listen address");
+
+        tx.send(addr).unwrap();
+
+        let future = listener
+            .filter_map(ListenerEvent::into_upgrade)
+            .into_future()
+            .map_err(|(err, _)| panic!("{:?}", err))
+            .and_then(|(client, _)| client.unwrap().0)
+            .map_err(|err| panic!("{:?}", err))
+            .and_then(|client| muxing::outbound_from_ref_and_wrap(Arc::new(client)))
+            .and_then(|client| {
+                tokio::io::read_to_end(client, vec![])
+            })
+            .and_then(|(_, msg)| {
+                assert_eq!(msg, b"hello world");
+                Ok(())
+            });
+
+        let mut rt = Runtime::new().unwrap();
+        let _ = rt.block_on(future).unwrap();
+    });
+
+    let transport = TcpConfig::new().with_upgrade(libp2p_mplex::MplexConfig::new());
+
+    let future = transport
+        .dial(rx.recv().unwrap())
+        .unwrap()
+        .map_err(|err| panic!("{:?}", err))
+        .and_then(|client| muxing::inbound_from_ref_and_wrap(Arc::new(client)))
+        .and_then(|server| tokio::io::write_all(server, b"hello world"))
+        .and_then(|(server, _)| {
+            tokio::io::shutdown(server)
+        })
+        .map(|_| ());
+
+    let mut rt = Runtime::new().unwrap();
+    let _ = rt.block_on(future).unwrap();
+    bg_thread.join().unwrap();
+}