From a9db219e50b7d27e48cd44e76941113a36b72e26 Mon Sep 17 00:00:00 2001
From: Lucio Franco <luciofranco14@gmail.com>
Date: Mon, 20 Mar 2023 13:04:46 -0400
Subject: [PATCH] fix(web): Fix `enable` and update docs (#1326)

* fix(web): Fix `enable` and update docs

* fix example, update deny

* fix namedservice path
---
 deny.toml                       |  1 +
 examples/src/grpc-web/server.rs | 10 +----
 tonic-web/src/lib.rs            | 75 +++++++++++++++++++++++++++------
 3 files changed, 63 insertions(+), 23 deletions(-)

diff --git a/deny.toml b/deny.toml
index ab45c04e8..aea2fb0de 100644
--- a/deny.toml
+++ b/deny.toml
@@ -18,6 +18,7 @@ skip-tree = [
     { name = "rustls-pemfile" },
     { name = "windows-sys" },
     { name = "hermit-abi" },
+    { name = "syn" },
 ]
 
 [licenses]
diff --git a/examples/src/grpc-web/server.rs b/examples/src/grpc-web/server.rs
index 0e8d51f32..7734a7663 100644
--- a/examples/src/grpc-web/server.rs
+++ b/examples/src/grpc-web/server.rs
@@ -2,8 +2,6 @@ use tonic::{transport::Server, Request, Response, Status};
 
 use hello_world::greeter_server::{Greeter, GreeterServer};
 use hello_world::{HelloReply, HelloRequest};
-use tonic_web::GrpcWebLayer;
-use tower_http::cors::CorsLayer;
 
 pub mod hello_world {
     tonic::include_proto!("helloworld");
@@ -41,13 +39,7 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
     Server::builder()
         // GrpcWeb is over http1 so we must enable it.
         .accept_http1(true)
-        // Use the Cors layer from `tower-http`.
-        .layer(CorsLayer::new())
-        // Apply the tonic-web layer to convert
-        // http1 requests into something that
-        // the core tonic code can understand.
-        .layer(GrpcWebLayer::new())
-        .add_service(greeter)
+        .add_service(tonic_web::enable(greeter))
         .serve(addr)
         .await?;
 
diff --git a/tonic-web/src/lib.rs b/tonic-web/src/lib.rs
index 00c2326f9..94f5f0f29 100644
--- a/tonic-web/src/lib.rs
+++ b/tonic-web/src/lib.rs
@@ -5,13 +5,6 @@
 //! with a [tower] service that performs the translation between protocols and handles `cors`
 //! requests.
 //!
-//! ## Getting Started
-//!
-//! ```toml
-//! [dependencies]
-//! tonic_web = "0.1"
-//! ```
-//!
 //! ## Enabling tonic services
 //!
 //! The easiest way to get started, is to call the [`enable`] function with your tonic service
@@ -31,12 +24,29 @@
 //!
 //!    Ok(())
 //! }
-//!
 //! ```
 //! This will apply a default configuration that works well with grpc-web clients out of the box.
 //!
 //! You can customize the CORS configuration composing the [`GrpcWebLayer`] with the cors layer of your choice.
 //!
+//! ```ignore
+//! #[tokio::main]
+//! async fn main() -> Result<(), Box<dyn std::error::Error>> {
+//!     let addr = "[::1]:50051".parse().unwrap();
+//!     let greeter = GreeterServer::new(MyGreeter::default());
+//!
+//!     Server::builder()
+//!        .accept_http1(true)
+//!        // This will apply the gRPC-Web translation layer
+//!        .layer(GrpcWebLayer::new())
+//!        .add_service(greeter)
+//!        .serve(addr)
+//!        .await?;
+//!
+//!    Ok(())
+//! }
+//! ```
+//!
 //! Alternatively, if you have a tls enabled server, you could skip setting `accept_http1` to `true`.
 //! This works because the browser will handle `ALPN`.
 //!
@@ -96,8 +106,8 @@ mod service;
 
 use http::header::HeaderName;
 use std::time::Duration;
-use tonic::body::BoxBody;
-use tower_http::cors::{AllowOrigin, Cors, CorsLayer};
+use tonic::{body::BoxBody, server::NamedService};
+use tower_http::cors::{AllowOrigin, CorsLayer};
 use tower_layer::Layer;
 use tower_service::Service;
 
@@ -112,14 +122,14 @@ type BoxError = Box<dyn std::error::Error + Send + Sync>;
 /// Enable a tonic service to handle grpc-web requests with the default configuration.
 ///
 /// You can customize the CORS configuration composing the [`GrpcWebLayer`] with the cors layer of your choice.
-pub fn enable<S>(service: S) -> Cors<GrpcWebService<S>>
+pub fn enable<S>(service: S) -> CorsGrpcWeb<S>
 where
     S: Service<http::Request<hyper::Body>, Response = http::Response<BoxBody>>,
     S: Clone + Send + 'static,
     S::Future: Send + 'static,
     S::Error: Into<BoxError> + Send,
 {
-    CorsLayer::new()
+    let cors = CorsLayer::new()
         .allow_origin(AllowOrigin::mirror_request())
         .allow_credentials(true)
         .max_age(DEFAULT_MAX_AGE)
@@ -136,8 +146,45 @@ where
                 .cloned()
                 .map(HeaderName::from_static)
                 .collect::<Vec<HeaderName>>(),
-        )
-        .layer(GrpcWebService::new(service))
+        );
+
+    tower_layer::layer_fn(|s| CorsGrpcWeb(cors.layer(s))).layer(GrpcWebService::new(service))
+}
+
+/// A newtype wrapper around [`GrpcWebLayer`] and [`tower_http::cors::CorsLayer`] to allow
+/// `tonic_web::enable` to implement the [`NamedService`] trait.
+#[derive(Debug, Clone)]
+pub struct CorsGrpcWeb<S>(tower_http::cors::Cors<GrpcWebService<S>>);
+
+impl<S> Service<http::Request<hyper::Body>> for CorsGrpcWeb<S>
+where
+    S: Service<http::Request<hyper::Body>, Response = http::Response<BoxBody>>,
+    S: Clone + Send + 'static,
+    S::Future: Send + 'static,
+    S::Error: Into<BoxError> + Send,
+{
+    type Response = S::Response;
+    type Error = S::Error;
+    type Future =
+        <tower_http::cors::Cors<GrpcWebService<S>> as Service<http::Request<hyper::Body>>>::Future;
+
+    fn poll_ready(
+        &mut self,
+        cx: &mut std::task::Context<'_>,
+    ) -> std::task::Poll<Result<(), Self::Error>> {
+        self.0.poll_ready(cx)
+    }
+
+    fn call(&mut self, req: http::Request<hyper::Body>) -> Self::Future {
+        self.0.call(req)
+    }
+}
+
+impl<S> NamedService for CorsGrpcWeb<S>
+where
+    S: NamedService,
+{
+    const NAME: &'static str = S::NAME;
 }
 
 pub(crate) mod util {