feat(util) Implement UnsyncBoxCloneService

tower/src/util/boxed_clone/mod.rs

@@ -0,0 +1,7 @@
+mod sync;
+mod unsync;
+
+#[allow(unreachable_pub)] // https://github.com/rust-lang/rust/issues/57411
+pub use self::{
+    sync::BoxCloneService, unsync::UnsyncBoxCloneService,
+};

tower/src/util/boxed_clone.rs → tower/src/util/boxed_clone/sync.rs

@@ -1,4 +1,4 @@
-use super::ServiceExt;
+use crate::ServiceExt;
 use futures_util::future::BoxFuture;
 use std::{
     fmt,

tower/src/util/boxed_clone/unsync.rs

@@ -0,0 +1,90 @@
+use crate::ServiceExt;
+use futures_util::future::LocalBoxFuture;
+use std::{
+    fmt,
+    task::{Context, Poll},
+};
+use tower_layer::{layer_fn, LayerFn};
+use tower_service::Service;
+
+/// A boxed [`CloneService`] trait object.
+///
+/// This type alias represents a boxed future that is *not* [`Send`] and must
+/// remain on the current thread.
+pub struct UnsyncBoxCloneService<T, U, E>(
+    Box<
+        dyn UnsyncCloneService<T, Response = U, Error = E, Future = LocalBoxFuture<'static, Result<U, E>>>
+    >,
+);
+
+impl<T, U, E> UnsyncBoxCloneService<T, U, E> {
+    /// Create a new `BoxCloneService`.
+    pub fn new<S>(inner: S) -> Self
+    where
+        S: Service<T, Response = U, Error = E> + Clone + 'static,
+        S::Future: 'static,
+    {
+        let inner = inner.map_future(|f| Box::pin(f) as _);
+        UnsyncBoxCloneService(Box::new(inner))
+    }
+
+    /// Returns a [`Layer`] for wrapping a [`Service`] in a [`BoxCloneService`]
+    /// middleware.
+    ///
+    /// [`Layer`]: crate::Layer
+    pub fn layer<S>() -> LayerFn<fn(S) -> Self>
+    where
+        S: Service<T, Response = U, Error = E> + Clone + 'static,
+        S::Future: 'static,
+    {
+        layer_fn(Self::new)
+    }
+}
+
+impl<T, U, E> Service<T> for UnsyncBoxCloneService<T, U, E> {
+    type Response = U;
+    type Error = E;
+    type Future = LocalBoxFuture<'static, Result<U, E>>;
+
+    #[inline]
+    fn poll_ready(&mut self, cx: &mut Context<'_>) -> Poll<Result<(), E>> {
+        self.0.poll_ready(cx)
+    }
+
+    #[inline]
+    fn call(&mut self, request: T) -> Self::Future {
+        self.0.call(request)
+    }
+}
+
+impl<T, U, E> Clone for UnsyncBoxCloneService<T, U, E> {
+    fn clone(&self) -> Self {
+        Self(self.0.clone_box())
+    }
+}
+
+trait UnsyncCloneService<R>: Service<R> {
+    fn clone_box(
+        &self,
+    ) -> Box<
+        dyn UnsyncCloneService<R, Response = Self::Response, Error = Self::Error, Future = Self::Future>,
+    >;
+}
+
+impl<R, T> UnsyncCloneService<R> for T
+where
+    T: Service<R> + Clone + 'static,
+{
+    fn clone_box(
+        &self,
+    ) -> Box<dyn UnsyncCloneService<R, Response = T::Response, Error = T::Error, Future = T::Future>>
+    {
+        Box::new(self.clone())
+    }
+}
+
+impl<T, U, E> fmt::Debug for UnsyncBoxCloneService<T, U, E> {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        fmt.debug_struct("BoxCloneService").finish()
+    }
+}

tower/src/util/mod.rs

@@ -24,7 +24,7 @@ pub mod rng;
 pub use self::{
     and_then::{AndThen, AndThenLayer},
     boxed::{BoxCloneServiceLayer, BoxLayer, BoxService, UnsyncBoxService},
-    boxed_clone::BoxCloneService,
+    boxed_clone::{BoxCloneService, UnsyncBoxCloneService},
     either::Either,
     future_service::{future_service, FutureService},
     map_err::{MapErr, MapErrLayer},

tower/tests/util/service_fn.rs

@@ -1,5 +1,5 @@
 use futures_util::future::ready;
-use tower::util::service_fn;
+use tower::util::{service_fn, UnsyncBoxCloneService};
 use tower_service::Service;
 
 #[tokio::test(flavor = "current_thread")]
@@ -10,3 +10,15 @@
     let answer = add_one.call(1).await.unwrap();
     assert_eq!(answer, 2);
 }
+
+#[tokio::test(flavor = "current_thread")]
+async fn boxed_clone() {
+    let _t = super::support::trace_init();
+    let x = std::rc::Rc::new(1);
+    let mut add_one = service_fn(|req| ready(Ok::<_, ()>(req + 1)));
+    let mut cloned = UnsyncBoxCloneService::new(add_one);
+    let answer = cloned.call(1).await.unwrap();
+    assert_eq!(answer, 2);
+    let answer = add_one.call(1).await.unwrap();
+    assert_eq!(answer, 2);
+}