server: Fix connection double-polling

src/server/mod.rs

@@ -4,7 +4,6 @@ use std::task::{self, Poll};
 
 use futures::io::{AsyncRead, AsyncWrite};
 use imap_codec::types::response::Capability;
-use tower::Service;
 
 use crate::proto::{Request, Response};
 use accept::Accept;
@@ -51,6 +50,7 @@ where
     S::MakeError: Into<Box<dyn std::error::Error + Send + Sync + 'static>> + std::fmt::Display,
     S::Error: std::fmt::Display,
     S::Future: Send + 'static,
+    S::Service: Send + 'static,
 {
     type Output = Result<(), Error<I::Error>>;
 
@@ -67,9 +67,9 @@ where
 
                 let service_fut = this.make_service.make_service_ref(&conn);
 
-                tokio::task::spawn(Connecting {
+                tokio::task::spawn(conn::Connecting {
                     conn,
-                    service_fut,
+                    state: conn::ConnectingState::Waiting { service_fut },
                     protocol: this.protocol.clone(),
                 });
             } else {
@@ -114,55 +114,92 @@ impl<I: Accept> Builder<I> {
     }
 }
 
-#[pin_project::pin_project]
-struct Connecting<C, F> {
-    conn: C,
-    #[pin]
-    service_fut: F,
-    protocol: Imap,
-}
+mod conn {
+    use std::future::Future;
+    use std::pin::Pin;
+    use std::task::{self, Poll};
 
-impl<C, F, ME, S> Future for Connecting<C, F>
-where
-    C: AsyncRead + AsyncWrite + Unpin,
-    F: Future<Output = std::result::Result<S, ME>>,
-    ME: std::fmt::Display,
-    S: Service<Request, Response = Response>,
-    S::Error: std::fmt::Display,
-{
-    type Output = ();
+    use futures::io::{AsyncRead, AsyncWrite};
+    use tower::Service;
 
-    fn poll(self: Pin<&mut Self>, cx: &mut task::Context<'_>) -> Poll<Self::Output> {
-        use tokio_tower::pipeline::Server as PipelineServer;
+    use super::Imap;
+    use crate::proto::{Request, Response};
 
-        use pipeline::Connection;
+    #[pin_project::pin_project]
+    pub struct Connecting<C, F, S> {
+        pub conn: C,
+        #[pin]
+        pub state: ConnectingState<F, S>,
+        pub protocol: Imap,
+    }
 
-        let this = self.project();
+    #[pin_project::pin_project(project = ConnectingStateProj)]
+    pub enum ConnectingState<F, S> {
+        Waiting {
+            #[pin]
+            service_fut: F,
+        },
+        Ready {
+            service: S,
+        },
+    }
 
-        let service = match futures::ready!(this.service_fut.poll(cx)) {
-            Ok(service) => service,
-            Err(err) => {
-                tracing::debug!("Connection error: {}", err);
-                return Poll::Ready(());
+    impl<C, F, ME, S> Future for Connecting<C, F, S>
+    where
+        C: AsyncRead + AsyncWrite + Unpin,
+        F: Future<Output = std::result::Result<S, ME>>,
+        ME: std::fmt::Display,
+        S: Service<Request, Response = Response>,
+        S::Error: std::fmt::Display,
+    {
+        type Output = ();
+
+        fn poll(self: Pin<&mut Self>, cx: &mut task::Context<'_>) -> Poll<Self::Output> {
+            use tokio_tower::pipeline::Server as PipelineServer;
+
+            use super::pipeline::Connection;
+
+            let mut this = self.project();
+
+            loop {
+                let next = match this.state.as_mut().project() {
+                    ConnectingStateProj::Waiting { service_fut } => {
+                        let service = match futures::ready!(service_fut.poll(cx)) {
+                            Ok(service) => service,
+                            Err(err) => {
+                                tracing::debug!("Connection error: {}", err);
+                                return Poll::Ready(());
+                            }
+                        };
+
+                        ConnectingState::Ready { service }
+                    }
+                    ConnectingStateProj::Ready { service } => {
+                        let mut conn = Connection::new(this.conn);
+
+                        // TODO: Properly handle server greeting
+                        {
+                            use imap_codec::types::response::{Response, Status};
+
+                            let status = Status::ok(None, None, "Hello").unwrap();
+                            let res = Response::Status(status);
+
+                            conn.send(res).unwrap();
+                        }
+
+                        let server = PipelineServer::new(conn, service);
+                        futures::pin_mut!(server);
+
+                        if let Err(err) = futures::ready!(server.poll(cx)) {
+                            tracing::debug!("Connection error: {}", err);
+                        }
+
+                        return Poll::Ready(());
+                    }
+                };
+
+                this.state.set(next);
             }
-        };
-        let mut conn = Connection::new(this.conn);
-
-        // TODO: Properly handle server greeting
-        {
-            use imap_codec::types::response::{Response, Status};
-
-            let status = Status::ok(None, None, "Hello").unwrap();
-            let res = Response::Status(status);
-
-            conn.send(res).unwrap();
         }
-
-        let mut server = PipelineServer::new(conn, service);
-        if let Err(err) = futures::ready!(Future::poll(Pin::new(&mut server), cx)) {
-            tracing::debug!("Connection error: {}", err);
-        }
-
-        Poll::Ready(())
     }
 }