fix(client): don't error on read before writing request

src/proto/conn.rs

@@ -238,7 +238,21 @@ where I: AsyncRead + AsyncWrite,
         ret
     }
 
-    pub fn maybe_park_read(&mut self) {
+    pub fn read_keep_alive(&mut self) -> Result<(), ::Error> {
+        debug_assert!(!self.can_read_head() && !self.can_read_body());
+
+        trace!("Conn::read_keep_alive");
+
+        if T::should_read_first() || !self.state.is_idle() {
+            self.maybe_park_read();
+        } else {
+            self.try_empty_read()?;
+        }
+
+        Ok(())
+    }
+
+    fn maybe_park_read(&mut self) {
         if !self.io.is_read_blocked() {
             // the Io object is ready to read, which means it will never alert
             // us that it is ready until we drain it. However, we're currently
@@ -258,7 +272,7 @@ where I: AsyncRead + AsyncWrite,
     //
     // This should only be called for Clients wanting to enter the idle
     // state.
-    pub fn try_empty_read(&mut self) -> io::Result<()> {
+    fn try_empty_read(&mut self) -> io::Result<()> {
         assert!(!self.can_read_head() && !self.can_read_body());
 
         if !self.io.read_buf().is_empty() {

src/proto/dispatch.rs

@@ -66,6 +66,20 @@ where
         self.conn.disable_keep_alive()
     }
 
+    fn poll2(&mut self) -> Poll<(), ::Error> {
+        self.poll_read()?;
+        self.poll_write()?;
+        self.poll_flush()?;
+
+        if self.is_done() {
+            try_ready!(self.conn.shutdown());
+            trace!("Dispatch::poll done");
+            Ok(Async::Ready(()))
+        } else {
+            Ok(Async::NotReady)
+        }
+    }
+
     fn poll_read(&mut self) -> Poll<(), ::Error> {
         loop {
             if self.is_closing {
@@ -163,12 +177,8 @@ where
                 } else {
                     // just drop, the body will close automatically
                 }
-            } else if !T::should_read_first() {
-                self.conn.try_empty_read()?;
-                return Ok(Async::NotReady);
             } else {
-                self.conn.maybe_park_read();
-                return Ok(Async::Ready(()));
+                return self.conn.read_keep_alive().map(Async::Ready);
             }
         }
     }
@@ -266,17 +276,13 @@ where
     #[inline]
     fn poll(&mut self) -> Poll<Self::Item, Self::Error> {
         trace!("Dispatcher::poll");
-        self.poll_read()?;
-        self.poll_write()?;
-        self.poll_flush()?;
-
-        if self.is_done() {
-            try_ready!(self.conn.shutdown());
-            trace!("Dispatch::poll done");
-            Ok(Async::Ready(()))
-        } else {
-            Ok(Async::NotReady)
-        }
+        self.poll2().or_else(|e| {
+            // An error means we're shutting down either way.
+            // We just try to give the error to the user,
+            // and close the connection with an Ok. If we
+            // cannot give it to the user, then return the Err.
+            self.dispatch.recv_msg(Err(e)).map(Async::Ready)
+        })
     }
 }
 
@@ -399,6 +405,9 @@ where
                 if let Some(cb) = self.callback.take() {
                     let _ = cb.send(Err(err));
                     Ok(())
+                } else if let Ok(Async::Ready(Some(ClientMsg::Request(_, _, cb)))) = self.rx.poll() {
+                    let _ = cb.send(Err(err));
+                    Ok(())
                 } else {
                     Err(err)
                 }
@@ -424,3 +433,39 @@ where
         self.callback.is_none()
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use futures::Sink;
+
+    use super::*;
+    use mock::AsyncIo;
+    use proto::ClientTransaction;
+
+    #[test]
+    fn client_read_response_before_writing_request() {
+        extern crate pretty_env_logger;
+        let _ = pretty_env_logger::try_init();
+        ::futures::lazy(|| {
+            let io = AsyncIo::new_buf(b"HTTP/1.1 200 OK\r\n\r\n".to_vec(), 100);
+            let (mut tx, rx) = mpsc::channel(0);
+            let conn = Conn::<_, ::Chunk, ClientTransaction>::new(io, Default::default());
+            let mut dispatcher = Dispatcher::new(Client::new(rx), conn);
+
+            let req = RequestHead {
+                version: ::HttpVersion::Http11,
+                subject: ::proto::RequestLine::default(),
+                headers: Default::default(),
+            };
+            let (res_tx, res_rx) = oneshot::channel();
+            tx.start_send(ClientMsg::Request(req, None::<::Body>, res_tx)).unwrap();
+
+            dispatcher.poll().expect("dispatcher poll 1");
+            dispatcher.poll().expect("dispatcher poll 2");
+            let _res = res_rx.wait()
+                .expect("callback poll")
+                .expect("callback response");
+            Ok::<(), ()>(())
+        }).wait().unwrap();
+    }
+}