diff --git a/tower-http/Cargo.toml b/tower-http/Cargo.toml
index b88ddeb3..c9de6366 100644
--- a/tower-http/Cargo.toml
+++ b/tower-http/Cargo.toml
@@ -68,6 +68,7 @@ full = [
"map-response-body",
"metrics",
"normalize-path",
+ "propagate-extension",
"propagate-header",
"redirect",
"request-id",
@@ -91,6 +92,7 @@ map-request-body = []
map-response-body = []
metrics = ["tokio/time"]
normalize-path = []
+propagate-extension = []
propagate-header = []
redirect = []
request-id = ["uuid"]
diff --git a/tower-http/src/builder.rs b/tower-http/src/builder.rs
index 2cb4f94a..5784274a 100644
--- a/tower-http/src/builder.rs
+++ b/tower-http/src/builder.rs
@@ -54,6 +54,16 @@ pub trait ServiceBuilderExt<L>: crate::sealed::Sealed<L> + Sized {
header: HeaderName,
) -> ServiceBuilder<Stack<crate::propagate_header::PropagateHeaderLayer, L>>;
+ /// Propagate an extension from the request to the response.
+ ///
+ /// See [`tower_http::propagate_extension`] for more details.
+ ///
+ /// [`tower_http::propagate_extension`]: crate::propagate_extension
+ #[cfg(feature = "propagate-extension")]
+ fn propagate_extension<T>(
+ self
+ ) -> ServiceBuilder<Stack<crate::propagate_extension::PropagateExtensionLayer<T>, L>>;
+
/// Add some shareable value to [request extensions].
///
/// See [`tower_http::add_extension`] for more details.
@@ -380,6 +390,13 @@ impl<L> ServiceBuilderExt<L> for ServiceBuilder<L> {
self.layer(crate::propagate_header::PropagateHeaderLayer::new(header))
}
+ #[cfg(feature = "propagate-extension")]
+ fn propagate_extension<X>(
+ self,
+ ) -> ServiceBuilder<Stack<crate::propagate_extension::PropagateExtensionLayer<X>, L>> {
+ self.layer(crate::propagate_extension::PropagateExtensionLayer::<X>::new())
+ }
+
#[cfg(feature = "add-extension")]
fn add_extension<T>(
self,
diff --git a/tower-http/src/compression/future.rs b/tower-http/src/compression/future.rs
index 426bb161..bfccff52 100644
--- a/tower-http/src/compression/future.rs
+++ b/tower-http/src/compression/future.rs
@@ -73,6 +73,7 @@ where
CompressionBody::new(BodyInner::zstd(WrapBody::new(body, self.quality)))
}
#[cfg(feature = "fs")]
+ #[allow(unreachable_patterns)]
(true, _) => {
// This should never happen because the `AcceptEncoding` struct which is used to determine
// `self.encoding` will only enable the different compression algorithms if the
diff --git a/tower-http/src/lib.rs b/tower-http/src/lib.rs
index 6719ddbd..a5777b24 100644
--- a/tower-http/src/lib.rs
+++ b/tower-http/src/lib.rs
@@ -231,6 +231,9 @@ pub mod auth;
#[cfg(feature = "set-header")]
pub mod set_header;
+#[cfg(feature = "propagate-extension")]
+pub mod propagate_extension;
+
#[cfg(feature = "propagate-header")]
pub mod propagate_header;
diff --git a/tower-http/src/propagate_extension.rs b/tower-http/src/propagate_extension.rs
new file mode 100644
index 00000000..3438cf2d
--- /dev/null
+++ b/tower-http/src/propagate_extension.rs
@@ -0,0 +1,248 @@
+//! Propagate an extension from the request to the response.
+//!
+//! This middleware is intended to wrap a Request->Response service handler that is _unaware_ of the
+//! extension. Consequently it _removes_ the extension from the request before forwarding the request, and then
+//! inserts it into the response when the response is ready. As a usage example, if you have pre-service mappers
+//! that need to share state with post-service mappers, you can store the state in the Request extensions,
+//! and this middleware will ensure that it is available to the post service mappers via the Response extensions.
+//!
+//! # Example
+//!
+//! ```rust
+//! use http::{Request, Response};
+//! use std::convert::Infallible;
+//! use tower::{Service, ServiceExt, ServiceBuilder, service_fn};
+//! use tower_http::add_extension::AddExtensionLayer;
+//! use tower_http::propagate_extension::PropagateExtensionLayer;
+//! use tower_http::ServiceBuilderExt;
+//! use hyper::Body;
+//!
+//! # #[tokio::main]
+//! # async fn main() -> Result<(), Box<dyn std::error::Error>> {
+//! async fn handle(req: Request<Body>) -> Result<Response<Body>, Infallible> {
+//! // ...
+//! # Ok(Response::new(Body::empty()))
+//! }
+//!
+//! //
+//! // Note that while the state object must _implement_ Clone, it should never actually
+//! // _be_ cloned due to the manner in which it is used within the middleware.
+//! //
+//! #[derive(Clone)]
+//! struct MyState {
+//! state_message: String
+//! };
+//!
+//! let my_state = MyState { state_message: "propagated state".to_string() };
+//!
+//! let mut svc = ServiceBuilder::new()
+//! .add_extension(my_state) // any other way of adding the extension to the request is OK too
+//! .propagate_extension::<MyState>()
+//! .service_fn(handle);
+//!
+//! // Call the service.
+//! let request = Request::builder()
+//! .body(Body::empty())?;
+//!
+//! let response = svc.ready().await?.call(request).await?;
+//!
+//! assert_eq!(response.extensions().get::<MyState>().unwrap().state_message, "propagated state");
+//! #
+//! # Ok(())
+//! # }
+//! ```
+
+use futures_util::ready;
+use http::{Request, Response};
+use pin_project_lite::pin_project;
+use std::future::Future;
+use std::{
+ pin::Pin,
+ task::{Context, Poll},
+ marker::PhantomData,
+};
+use tower_layer::Layer;
+use tower_service::Service;
+
+#[allow(unused_imports)]
+use tracing::{
+ trace,
+ debug,
+ info,
+ warn,
+ error,
+};
+
+/// Layer that applies [`PropagateExtension`] which propagates an extension from the request to the response.
+///
+/// This middleware is intended to wrap a Request->Response service handler that is _unaware_ of the
+/// extension. Consequently it _removes_ the extension from the request before forwarding the request, and then
+/// inserts it into the response when the response is ready. As a usage example, if you have pre-service mappers
+/// that need to share state with post-service mappers, you can store the state in the Request extensions,
+/// and this middleware will ensure that it is available to the post service mappers via the Response extensions.
+///
+/// See the [module docs](crate::propagate_extension) for more details.
+#[derive(Clone, Debug)]
+pub struct PropagateExtensionLayer<X> {
+ _phantom: PhantomData<X>
+}
+
+impl<X> PropagateExtensionLayer<X> {
+ /// Create a new [`PropagateExtensionLayer`].
+ pub fn new() -> Self {
+ Self { _phantom: PhantomData }
+ }
+}
+
+impl<S,X> Layer<S> for PropagateExtensionLayer<X> {
+ type Service = PropagateExtension<S,X>;
+
+ fn layer(&self, inner: S) -> Self::Service {
+ PropagateExtension::<S,X> {
+ inner,
+ _phantom: PhantomData
+ }
+ }
+}
+
+/// Middleware that propagates extensions from requests to responses.
+///
+/// If the extension is present on the request it'll be removed from the request and
+/// inserted into the response.
+///
+/// See the [module docs](crate::propagate_extension) for more details.
+#[derive(Clone,Debug)]
+pub struct PropagateExtension<S,X> {
+ inner: S,
+ _phantom: PhantomData<X>
+}
+
+impl<S,X> PropagateExtension<S,X> {
+ /// Create a new [`PropagateExtension`] that propagates the given extension type.
+ pub fn new(inner: S) -> Self {
+ Self { inner, _phantom: PhantomData }
+ }
+
+ define_inner_service_accessors!();
+
+ /// Returns a new [`Layer`] that wraps services with a `PropagateExtension` middleware.
+ ///
+ /// [`Layer`]: tower_layer::Layer
+ pub fn layer() -> PropagateExtensionLayer<X> {
+ PropagateExtensionLayer::<X>::new()
+ }
+}
+
+impl<ReqBody, ResBody, S, X> Service<Request<ReqBody>> for PropagateExtension<S,X>
+where
+ X: Sync + Send + 'static,
+ S: Service<Request<ReqBody>, Response = Response<ResBody>>,
+{
+ type Response = S::Response;
+ type Error = S::Error;
+ type Future = ResponseFuture<S::Future,X>;
+
+ #[inline]
+ fn poll_ready(&mut self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
+ self.inner.poll_ready(cx)
+ }
+
+ fn call(&mut self, mut req: Request<ReqBody>) -> Self::Future {
+ let extension: Option<X> = req.extensions_mut().remove();
+ debug!("Removed state from request extensions. is_some? {}", extension.is_some());
+
+ ResponseFuture {
+ future: self.inner.call(req),
+ extension,
+ }
+ }
+}
+
+pin_project! {
+ /// Response future for [`PropagateExtension`].
+ #[derive(Debug)]
+ pub struct ResponseFuture<F,X> {
+ #[pin]
+ future: F,
+ extension: Option<X>,
+ }
+}
+
+impl<F, ResBody, E, X> Future for ResponseFuture<F,X>
+where
+ X: Sync + Send + 'static,
+ F: Future<Output = Result<Response<ResBody>, E>>,
+{
+ type Output = F::Output;
+
+ fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+ let this = self.project();
+ let mut res = ready!(this.future.poll(cx)?);
+
+ if let Some(extension) = this.extension.take() {
+ debug!("Inserting state into response extensions");
+ res.extensions_mut().insert(extension);
+ } else {
+ debug!("No state to insert into response");
+ }
+
+ Poll::Ready(Ok(res))
+ }
+}
+
+#[cfg(test)]
+mod tests {
+ use super::*;
+
+ use http::{Request, Response};
+ use std::convert::Infallible;
+ use tower::{Service, ServiceExt, ServiceBuilder};
+ use crate::add_extension::AddExtensionLayer;
+ use crate::builder::ServiceBuilderExt;
+ use hyper::Body;
+
+ async fn handle(_req: Request<Body>) -> Result<Response<Body>, Infallible> {
+ Ok(Response::new(Body::empty()))
+ }
+
+ #[derive(Clone)]
+ struct MyState {
+ state_message: String
+ }
+
+ #[test]
+ fn basic_test() {
+
+ let my_state = MyState { state_message: "propagated state".to_string() };
+
+ let mut svc = ServiceBuilder::new()
+ .layer(AddExtensionLayer::new(my_state)) // any other way of adding the extension to the request is OK too
+ .layer(PropagateExtensionLayer::<MyState>::new())
+ .service_fn(handle);
+
+ let request = Request::builder().body(Body::empty()).expect("Expected an empty body");
+
+ // Call the service.
+ let ready = futures::executor::block_on(svc.ready()).expect("Expected the service to be ready");
+ let response = futures::executor::block_on(ready.call(request)).expect("Expected the service to be successful");
+ assert_eq!(response.extensions().get::<MyState>().unwrap().state_message, "propagated state");
+ }
+
+ #[test]
+ fn test_server_builder_ext() {
+
+ let my_state = MyState { state_message: "propagated state".to_string() };
+
+ let mut svc = ServiceBuilder::new()
+ .add_extension(my_state) // any other way of adding the extension to the request is OK too
+ .propagate_extension::<MyState>()
+ .service_fn(handle);
+
+ let request = Request::builder().body(Body::empty()).expect("Expected an empty body");
+
+ // Call the service.
+ let ready = futures::executor::block_on(svc.ready()).expect("Expected the service to be ready");
+ let response = futures::executor::block_on(ready.call(request)).expect("Expected the service to be successful");
+ assert_eq!(response.extensions().get::<MyState>().unwrap().state_message, "propagated state");
+ }
+}