Add an error associated type to ProtocolsHandler (#795)

core/src/protocols_handler/dummy.rs

@@ -27,7 +27,7 @@ use crate::{
     }
 };
 use futures::prelude::*;
-use std::{io, marker::PhantomData};
+use std::marker::PhantomData;
 use tokio_io::{AsyncRead, AsyncWrite};
 use void::Void;
 
@@ -53,6 +53,7 @@ where
 {
     type InEvent = Void;
     type OutEvent = Void;
+    type Error = Void;
     type Substream = TSubstream;
     type InboundProtocol = DeniedUpgrade;
     type OutboundProtocol = DeniedUpgrade;
@@ -97,7 +98,7 @@ where
         &mut self,
     ) -> Poll<
         Option<ProtocolsHandlerEvent<Self::OutboundProtocol, Self::OutboundOpenInfo, Self::OutEvent>>,
-        io::Error,
+        Void,
     > {
         if self.shutting_down {
             Ok(Async::Ready(None))

core/src/protocols_handler/map_in.rs

@@ -26,7 +26,7 @@ use crate::{
     }
 };
 use futures::prelude::*;
-use std::{io, marker::PhantomData};
+use std::marker::PhantomData;
 
 /// Wrapper around a protocol handler that turns the input event into something else.
 pub struct MapInEvent<TProtoHandler, TNewIn, TMap> {
@@ -54,6 +54,7 @@ where
 {
     type InEvent = TNewIn;
     type OutEvent = TProtoHandler::OutEvent;
+    type Error = TProtoHandler::Error;
     type Substream = TProtoHandler::Substream;
     type InboundProtocol = TProtoHandler::InboundProtocol;
     type OutboundProtocol = TProtoHandler::OutboundProtocol;
@@ -108,7 +109,7 @@ where
         &mut self,
     ) -> Poll<
         Option<ProtocolsHandlerEvent<Self::OutboundProtocol, Self::OutboundOpenInfo, Self::OutEvent>>,
-        io::Error,
+        Self::Error,
     > {
         self.inner.poll()
     }

core/src/protocols_handler/map_out.rs

@@ -26,7 +26,6 @@ use crate::{
     }
 };
 use futures::prelude::*;
-use std::io;
 
 /// Wrapper around a protocol handler that turns the output event into something else.
 pub struct MapOutEvent<TProtoHandler, TMap> {
@@ -52,6 +51,7 @@ where
 {
     type InEvent = TProtoHandler::InEvent;
     type OutEvent = TNewOut;
+    type Error = TProtoHandler::Error;
     type Substream = TProtoHandler::Substream;
     type InboundProtocol = TProtoHandler::InboundProtocol;
     type OutboundProtocol = TProtoHandler::OutboundProtocol;
@@ -104,7 +104,7 @@ where
         &mut self,
     ) -> Poll<
         Option<ProtocolsHandlerEvent<Self::OutboundProtocol, Self::OutboundOpenInfo, Self::OutEvent>>,
-        io::Error,
+        Self::Error,
     > {
         Ok(self.inner.poll()?.map(|ev| {
             ev.map(|ev| match ev {

core/src/protocols_handler/mod.rs

@@ -24,7 +24,7 @@ use crate::upgrade::{
     UpgradeError,
 };
 use futures::prelude::*;
-use std::{error, fmt, io, time::Duration};
+use std::{error, fmt, time::Duration};
 use tokio_io::{AsyncRead, AsyncWrite};
 
 pub use self::dummy::DummyProtocolsHandler;
@@ -89,6 +89,8 @@ pub trait ProtocolsHandler {
     type InEvent;
     /// Custom event that can be produced by the handler and that will be returned to the outside.
     type OutEvent;
+    /// Error that can happen when polling.
+    type Error: error::Error;
     /// The type of the substream that contains the raw data.
     type Substream: AsyncRead + AsyncWrite;
     /// The upgrade for the protocol or protocols handled by this handler.
@@ -144,7 +146,7 @@ pub trait ProtocolsHandler {
     /// > **Note**: If this handler is combined with other handlers, as soon as `poll()` returns
     /// >           `Ok(Async::Ready(None))`, all the other handlers will receive a call to
     /// >           `shutdown()` and will eventually be closed and destroyed.
-    fn poll(&mut self) -> Poll<Option<ProtocolsHandlerEvent<Self::OutboundProtocol, Self::OutboundOpenInfo, Self::OutEvent>>, io::Error>;
+    fn poll(&mut self) -> Poll<Option<ProtocolsHandlerEvent<Self::OutboundProtocol, Self::OutboundOpenInfo, Self::OutEvent>>, Self::Error>;
 
     /// Adds a closure that turns the input event into something else.
     #[inline]

core/src/protocols_handler/node_handler.rs

@@ -29,7 +29,7 @@ use crate::{
     }
 };
 use futures::prelude::*;
-use std::{io, time::Duration};
+use std::time::Duration;
 use tokio_timer::Timeout;
 
 /// Prototype for a `NodeHandlerWrapper`.
@@ -123,7 +123,7 @@ where
 {
     type InEvent = TProtoHandler::InEvent;
     type OutEvent = TProtoHandler::OutEvent;
-    type Error = io::Error;       // TODO: better error type
+    type Error = TProtoHandler::Error;
     type Substream = TProtoHandler::Substream;
     // The first element of the tuple is the unique upgrade identifier
     // (see `unique_dial_upgrade_id`).
@@ -198,7 +198,7 @@ where
         self.handler.shutdown();
     }
 
-    fn poll(&mut self) -> Poll<Option<NodeHandlerEvent<Self::OutboundOpenInfo, Self::OutEvent>>, io::Error> {
+    fn poll(&mut self) -> Poll<Option<NodeHandlerEvent<Self::OutboundOpenInfo, Self::OutEvent>>, Self::Error> {
         // Continue negotiation of newly-opened substreams on the listening side.
         // We remove each element from `negotiating_in` one by one and add them back if not ready.
         for n in (0..self.negotiating_in.len()).rev() {

core/src/protocols_handler/select.rs

@@ -31,7 +31,6 @@ use crate::{
     }
 };
 use futures::prelude::*;
-use std::io;
 use tokio_io::{AsyncRead, AsyncWrite};
 
 /// Implementation of `ProtocolsHandler` that combines two protocols into one.
@@ -65,6 +64,7 @@ where
 {
     type InEvent = EitherOutput<TProto1::InEvent, TProto2::InEvent>;
     type OutEvent = EitherOutput<TProto1::OutEvent, TProto2::OutEvent>;
+    type Error = EitherError<TProto1::Error, TProto2::Error>;
     type Substream = TSubstream;
     type InboundProtocol = SelectUpgrade<TProto1::InboundProtocol, TProto2::InboundProtocol>;
     type OutboundProtocol = EitherUpgrade<TProto1::OutboundProtocol, TProto2::OutboundProtocol>;
@@ -161,8 +161,8 @@ where
         self.proto2.shutdown();
     }
 
-    fn poll(&mut self) -> Poll<Option<ProtocolsHandlerEvent<Self::OutboundProtocol, Self::OutboundOpenInfo, Self::OutEvent>>, io::Error> {
-        match self.proto1.poll()? {
+    fn poll(&mut self) -> Poll<Option<ProtocolsHandlerEvent<Self::OutboundProtocol, Self::OutboundOpenInfo, Self::OutEvent>>, Self::Error> {
+        match self.proto1.poll().map_err(EitherError::A)? {
             Async::Ready(Some(ProtocolsHandlerEvent::Custom(event))) => {
                 return Ok(Async::Ready(Some(ProtocolsHandlerEvent::Custom(EitherOutput::First(event)))));
             },
@@ -176,7 +176,7 @@ where
             Async::NotReady => ()
         };
 
-        match self.proto2.poll()? {
+        match self.proto2.poll().map_err(EitherError::B)? {
             Async::Ready(Some(ProtocolsHandlerEvent::Custom(event))) => {
                 return Ok(Async::Ready(Some(ProtocolsHandlerEvent::Custom(EitherOutput::Second(event)))));
             },