chore: remove tower dep by vendoring Oneshot

Cargo.toml

@@ -28,8 +28,7 @@ futures-channel = { version = "0.3", optional = true }
 socket2 = { version = "0.5", optional = true, features = ["all"] }
 tracing = { version = "0.1", default-features = false, features = ["std"], optional = true }
 tokio = { version = "1", optional = true, default-features = false  }
-tower-service ={ version = "0.3", optional = true }
-tower = { version = "0.4.1", optional = true, default-features = false, features = ["make", "util"] }
+tower-service = { version = "0.3", optional = true }
 
 [dev-dependencies]
 hyper = { version = "1.4.0", features = ["full"] }
@@ -58,14 +57,14 @@ full = [
     "tokio",
 ]
 
-client = ["hyper/client", "dep:tracing", "dep:futures-channel", "dep:tower", "dep:tower-service"]
+client = ["hyper/client", "dep:tracing", "dep:futures-channel", "dep:tower-service"]
 client-legacy = ["client", "dep:socket2", "tokio/sync"]
 
 server = ["hyper/server"]
 server-auto = ["server", "http1", "http2"]
-server-graceful = ["server", "tokio/sync"]
+server-graceful = ["server", "tokio/sync", "futures-util/alloc"]
 
-service = ["dep:tower", "dep:tower-service"]
+service = ["dep:tower-service"]
 
 http1 = ["hyper/http1"]
 http2 = ["hyper/http2"]

src/client/legacy/connect/mod.rs

@@ -343,8 +343,8 @@ pub(super) mod sealed {
     {
         type _Svc = S;
 
-        fn connect(self, _: Internal, dst: Uri) -> tower::util::Oneshot<S, Uri> {
-            tower::util::Oneshot::new(self, dst)
+        fn connect(self, _: Internal, dst: Uri) -> crate::service::Oneshot<S, Uri> {
+            crate::service::Oneshot::new(self, dst)
         }
     }
 
@@ -357,10 +357,10 @@ pub(super) mod sealed {
     {
         type Connection = T;
         type Error = S::Error;
-        type Future = tower::util::Oneshot<S, Uri>;
+        type Future = crate::service::Oneshot<S, Uri>;
 
         fn connect(self, _: Internal, dst: Uri) -> Self::Future {
-            tower::util::Oneshot::new(self, dst)
+            crate::service::Oneshot::new(self, dst)
         }
     }
 

src/service.rs

@@ -6,7 +6,8 @@ use std::{
     pin::Pin,
     task::{Context, Poll},
 };
-use tower::{util::Oneshot, ServiceExt};
+
+pub(crate) use self::internal::Oneshot;
 
 /// A tower service converted into a hyper service.
 #[derive(Debug, Copy, Clone)]
@@ -33,7 +34,7 @@ where
 
     fn call(&self, req: R) -> Self::Future {
         TowerToHyperServiceFuture {
-            future: self.service.clone().oneshot(req),
+            future: Oneshot::new(self.service.clone(), req),
         }
     }
 }
@@ -60,3 +61,66 @@ where
         self.project().future.poll(cx)
     }
 }
+
+mod internal {
+    use pin_project_lite::pin_project;
+    use std::future::Future;
+    use std::pin::Pin;
+    use std::task::{ready, Context, Poll};
+    use tower_service::Service;
+
+    // Not really pub, but used in a trait for bounds
+    pin_project! {
+        #[project = OneshotProj]
+        #[derive(Debug)]
+        pub enum Oneshot<S: Service<Req>, Req> {
+            NotReady {
+                svc: S,
+                req: Option<Req>,
+            },
+            Called {
+                #[pin]
+                fut: S::Future,
+            },
+            Done,
+        }
+    }
+
+    impl<S, Req> Oneshot<S, Req>
+    where
+        S: Service<Req>,
+    {
+        pub(crate) const fn new(svc: S, req: Req) -> Self {
+            Oneshot::NotReady {
+                svc,
+                req: Some(req),
+            }
+        }
+    }
+
+    impl<S, Req> Future for Oneshot<S, Req>
+    where
+        S: Service<Req>,
+    {
+        type Output = Result<S::Response, S::Error>;
+
+        fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+            loop {
+                let this = self.as_mut().project();
+                match this {
+                    OneshotProj::NotReady { svc, req } => {
+                        let _ = ready!(svc.poll_ready(cx))?;
+                        let fut = svc.call(req.take().expect("already called"));
+                        self.set(Oneshot::Called { fut });
+                    }
+                    OneshotProj::Called { fut } => {
+                        let res = ready!(fut.poll(cx))?;
+                        self.set(Oneshot::Done);
+                        return Poll::Ready(Ok(res));
+                    }
+                    OneshotProj::Done => panic!("polled after complete"),
+                }
+            }
+        }
+    }
+}