[multistream-select] Fix panic with V1Lazy (regression) and more convenient transport boxing. (#1783)

* [multistream-select] Fix panic with V1Lazy and add integration tests.

Fixes a panic when using the `V1Lazy` negotiation protocol,
a regression introduced in https://github.com/libp2p/rust-libp2p/pull/1484.

Thereby adds integration tests for a transport upgrade with both
`V1` and `V1Lazy` to the `multistream-select` crate to prevent
future regressions.

* Cleanup.

* Update changelog.

core/src/transport.rs

@@ -25,14 +25,13 @@
 //! any desired protocols. The rest of the module defines combinators for
 //! modifying a transport through composition with other transports or protocol upgrades.
 
-use crate::ConnectedPoint;
+use crate::{ConnectedPoint, ConnectionInfo, muxing::{StreamMuxer, StreamMuxerBox}};
 use futures::prelude::*;
 use multiaddr::Multiaddr;
 use std::{error::Error, fmt};
 use std::time::Duration;
 
 pub mod and_then;
-pub mod boxed;
 pub mod choice;
 pub mod dummy;
 pub mod map;
@@ -41,8 +40,10 @@ pub mod memory;
 pub mod timeout;
 pub mod upgrade;
 
+mod boxed;
 mod optional;
 
+pub use self::boxed::Boxed;
 pub use self::choice::OrTransport;
 pub use self::memory::MemoryTransport;
 pub use self::optional::OptionalTransport;
@@ -128,14 +129,24 @@ pub trait Transport {
     where
         Self: Sized;
 
-    /// Turns the transport into an abstract boxed (i.e. heap-allocated) transport.
-    fn boxed(self) -> boxed::Boxed<Self::Output, Self::Error>
-    where Self: Sized + Clone + Send + Sync + 'static,
-          Self::Dial: Send + 'static,
-          Self::Listener: Send + 'static,
-          Self::ListenerUpgrade: Send + 'static,
+    /// Boxes an authenticated, multiplexed transport, including the
+    /// `StreamMuxer` and transport errors.
+    fn boxed<I, M>(self) -> boxed::Boxed<(I, StreamMuxerBox), std::io::Error>
+    where
+        Self: Transport<Output = (I, M)> + Sized + Clone + Send + Sync + 'static,
+        Self::Dial: Send + 'static,
+        Self::Listener: Send + 'static,
+        Self::ListenerUpgrade: Send + 'static,
+        Self::Error: Send + Sync,
+        I: ConnectionInfo,
+        M: StreamMuxer + Send + Sync + 'static,
+        M::Substream: Send + 'static,
+        M::OutboundSubstream: Send + 'static
+
     {
-        boxed::boxed(self)
+        boxed::boxed(
+            self.map(|(i, m), _| (i, StreamMuxerBox::new(m)))
+                .map_err(|e| std::io::Error::new(std::io::ErrorKind::Other, e)))
     }
 
     /// Applies a function on the connections created by the transport.

core/src/transport/boxed.rs

@@ -24,7 +24,6 @@ use multiaddr::Multiaddr;
 use std::{error, fmt, pin::Pin, sync::Arc};
 
 /// See the `Transport::boxed` method.
-#[inline]
 pub fn boxed<T>(transport: T) -> Boxed<T::Output, T::Error>
 where
     T: Transport + Clone + Send + Sync + 'static,
@@ -37,9 +36,14 @@ where
     }
 }
 
-pub type Dial<O, E> = Pin<Box<dyn Future<Output = Result<O, E>> + Send>>;
-pub type Listener<O, E> = Pin<Box<dyn Stream<Item = Result<ListenerEvent<ListenerUpgrade<O, E>, E>, E>> + Send>>;
-pub type ListenerUpgrade<O, E> = Pin<Box<dyn Future<Output = Result<O, E>> + Send>>;
+/// See the `Transport::boxed` method.
+pub struct Boxed<O, E> {
+    inner: Arc<dyn Abstract<O, E> + Send + Sync>,
+}
+
+type Dial<O, E> = Pin<Box<dyn Future<Output = Result<O, E>> + Send>>;
+type Listener<O, E> = Pin<Box<dyn Stream<Item = Result<ListenerEvent<ListenerUpgrade<O, E>, E>, E>> + Send>>;
+type ListenerUpgrade<O, E> = Pin<Box<dyn Future<Output = Result<O, E>> + Send>>;
 
 trait Abstract<O, E> {
     fn listen_on(&self, addr: Multiaddr) -> Result<Listener<O, E>, TransportError<E>>;
@@ -68,11 +72,6 @@ where
     }
 }
 
-/// See the `Transport::boxed` method.
-pub struct Boxed<O, E> {
-    inner: Arc<dyn Abstract<O, E> + Send + Sync>,
-}
-
 impl<O, E> fmt::Debug for Boxed<O, E> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         write!(f, "BoxedTransport")