Use 'async_trait' for 'Fairing' trait.

Also re-exports the 'async_trait' attribute from 'rocket'.

contrib/lib/src/helmet/helmet.rs

@@ -188,6 +188,7 @@ impl SpaceHelmet {
     }
 }
 
+#[rocket::async_trait]
 impl Fairing for SpaceHelmet {
     fn info(&self) -> Info {
         Info {
@@ -196,10 +197,8 @@ impl Fairing for SpaceHelmet {
         }
     }
 
-    fn on_response<'a>(&'a self, _request: &'a Request<'_>, response: &'a mut Response<'_>) -> std::pin::Pin<Box<dyn std::future::Future<Output=()> + Send + 'a>> {
+    async fn on_response<'a>(&'a self, _: &'a Request<'_>, res: &'a mut Response<'_>) {
-        Box::pin(async move {
+        self.apply(res);
-            self.apply(response);
-        })
     }
 
     fn on_launch(&self, rocket: &Rocket) {

contrib/lib/src/templates/fairing.rs

@@ -124,17 +124,26 @@ pub struct TemplateFairing {
     pub custom_callback: Box<dyn Fn(&mut Engines) + Send + Sync + 'static>,
 }
 
+#[rocket::async_trait]
 impl Fairing for TemplateFairing {
     fn info(&self) -> Info {
         // The on_request part of this fairing only applies in debug
         // mode, so only register it in debug mode.
-        Info {
-            name: "Templates",
         #[cfg(debug_assertions)]
+        let info = Info {
+            name: "Templates",
             kind: Kind::Attach | Kind::Request,
+        };
+
+        // FIXME: We declare two `info` variables here, instead of just one with
+        // `cfg`s on `kind`, due to issue #63 in `async_trait`.
         #[cfg(not(debug_assertions))]
+        let info = Info {
+            name: "Templates",
             kind: Kind::Attach,
-        }
+        };
+
+        info
     }
 
     /// Initializes the template context. Templates will be searched for in the
@@ -163,14 +172,10 @@ impl Fairing for TemplateFairing {
     }
 
     #[cfg(debug_assertions)]
-    fn on_request<'a>(&'a self, req: &'a mut rocket::Request<'_>, _data: &'a rocket::Data)
+    async fn on_request<'a>(&'a self, req: &'a mut rocket::Request<'_>, _data: &'a rocket::Data) {
-        -> std::pin::Pin<Box<dyn std::future::Future<Output=()> + Send + 'a>>
-    {
-        Box::pin(async move {
         let cm = req.guard::<rocket::State<'_, ContextManager>>()
             .expect("Template ContextManager registered in on_attach");
 
         cm.reload_if_needed(&*self.custom_callback);
-        })
     }
 }

core/codegen/tests/async-routes.rs

@@ -1,4 +1,5 @@
 #![feature(proc_macro_hygiene)]
+#![allow(dead_code)]
 
 #[macro_use] extern crate rocket;
 use rocket::http::uri::Origin;

core/lib/Cargo.toml

@@ -39,6 +39,7 @@ memchr = "2" # TODO: Use pear instead.
 binascii = "0.1"
 pear = "0.1"
 atty = "0.2"
+async-trait = "0.1"
 
 [build-dependencies]
 yansi = "0.5"

core/lib/src/fairing/ad_hoc.rs

@@ -68,8 +68,8 @@ impl AdHoc {
     /// // The no-op attach fairing.
     /// let fairing = AdHoc::on_attach("No-Op", |rocket| Ok(rocket));
     /// ```
-    pub fn on_attach<F>(name: &'static str, f: F) -> AdHoc
+    pub fn on_attach<F: Send + 'static>(name: &'static str, f: F) -> AdHoc
-        where F: FnOnce(Rocket) -> Result<Rocket, Rocket> + Send + 'static
+        where F: FnOnce(Rocket) -> Result<Rocket, Rocket>
     {
         AdHoc { name, kind: AdHocKind::Attach(Mutex::new(Some(Box::new(f)))) }
     }
@@ -87,8 +87,8 @@ impl AdHoc {
     ///     println!("Launching in T-3..2..1..");
     /// });
     /// ```
-    pub fn on_launch<F>(name: &'static str, f: F) -> AdHoc
+    pub fn on_launch<F: Send + 'static>(name: &'static str, f: F) -> AdHoc
-        where F: FnOnce(&Rocket) + Send + 'static
+        where F: FnOnce(&Rocket)
     {
         AdHoc { name, kind: AdHocKind::Launch(Mutex::new(Some(Box::new(f)))) }
     }
@@ -110,8 +110,8 @@ impl AdHoc {
     ///     })
     /// });
     /// ```
-    pub fn on_request<F>(name: &'static str, f: F) -> AdHoc
+    pub fn on_request<F: Send + Sync + 'static>(name: &'static str, f: F) -> AdHoc
-        where F: for<'a> Fn(&'a mut Request<'_>, &'a Data) -> BoxFuture<'a, ()> + Send + Sync + 'static
+        where F: for<'a> Fn(&'a mut Request<'_>, &'a Data) -> BoxFuture<'a, ()>
     {
         AdHoc { name, kind: AdHocKind::Request(Box::new(f)) }
     }
@@ -133,13 +133,14 @@ impl AdHoc {
     ///     })
     /// });
     /// ```
-    pub fn on_response<F>(name: &'static str, f: F) -> AdHoc
+    pub fn on_response<F: Send + Sync + 'static>(name: &'static str, f: F) -> AdHoc
-        where F: for<'a> Fn(&'a Request<'_>, &'a mut Response<'_>) -> BoxFuture<'a, ()> + Send + Sync + 'static
+        where F: for<'a> Fn(&'a Request<'_>, &'a mut Response<'_>) -> BoxFuture<'a, ()>
     {
         AdHoc { name, kind: AdHocKind::Response(Box::new(f)) }
     }
 }
 
+#[crate::async_trait]
 impl Fairing for AdHoc {
     fn info(&self) -> Info {
         let kind = match self.kind {
@@ -170,19 +171,15 @@ impl Fairing for AdHoc {
         }
     }
 
-    fn on_request<'a>(&'a self, request: &'a mut Request<'_>, data: &'a Data) -> BoxFuture<'a, ()> {
+    async fn on_request<'a>(&'a self, req: &'a mut Request<'_>, data: &'a Data) {
         if let AdHocKind::Request(ref callback) = self.kind {
-            callback(request, data)
+            callback(req, data).await;
-        } else {
-            Box::pin(async { })
         }
     }
 
-    fn on_response<'a>(&'a self, request: &'a Request<'_>, response: &'a mut Response<'_>) -> BoxFuture<'a, ()> {
+    async fn on_response<'a>(&'a self, req: &'a Request<'_>, res: &'a mut Response<'_>) {
         if let AdHocKind::Response(ref callback) = self.kind {
-            callback(request, response)
+            callback(req, res).await;
-        } else {
-            Box::pin(async { })
         }
     }
 }

core/lib/src/fairing/mod.rs

@@ -47,8 +47,6 @@
 //! of other `Fairings` are not jeopardized. For instance, unless it is made
 //! abundantly clear, a fairing should not rewrite every request.
 
-use futures_util::future::BoxFuture;
-
 use crate::{Rocket, Request, Response, Data};
 
 mod fairings;
@@ -138,7 +136,7 @@ pub use self::info_kind::{Info, Kind};
 ///     to the request; these issues are better handled via [request guards] or
 ///     via response callbacks. Any modifications to a request are persisted and
 ///     can potentially alter how a request is routed.
-///=
+///
 ///   * **Response (`on_response`)**
 ///
 ///     A response callback, represented by the [`Fairing::on_response()`]
@@ -192,6 +190,45 @@ pub use self::info_kind::{Info, Kind};
 /// these bounds _do not_ prohibit a `Fairing` from holding state: the state
 /// need simply be thread-safe and statically available or heap allocated.
 ///
+/// ## Async Trait
+///
+/// [`Fairing`] is an _async_ trait. Implementations of `Fairing` must be
+/// decorated with an attribute of `#[rocket::async_trait]`:
+///
+/// ```rust
+/// use rocket::{Rocket, Request, Data, Response};
+/// use rocket::fairing::{Fairing, Info, Kind};
+///
+/// # struct MyType;
+/// #[rocket::async_trait]
+/// impl Fairing for MyType {
+///     fn info(&self) -> Info {
+///         /* ... */
+///         # unimplemented!()
+///     }
+///
+///     fn on_attach(&self, rocket: Rocket) -> Result<Rocket, Rocket> {
+///         /* ... */
+///         # unimplemented!()
+///     }
+///
+///     fn on_launch(&self, rocket: &Rocket) {
+///         /* ... */
+///         # unimplemented!()
+///     }
+///
+///     async fn on_request<'a>(&'a self, req: &'a mut Request<'_>, data: &'a Data) {
+///         /* ... */
+///         # unimplemented!()
+///     }
+///
+///     async fn on_response<'a>(&'a self, req: &'a Request<'_>, res: &'a mut Response<'_>) {
+///         /* ... */
+///         # unimplemented!()
+///     }
+/// }
+/// ```
+///
 /// ## Example
 ///
 /// Imagine that we want to record the number of `GET` and `POST` requests that
@@ -220,6 +257,7 @@ pub use self::info_kind::{Info, Kind};
 ///     post: AtomicUsize,
 /// }
 ///
+/// #[rocket::async_trait]
 /// impl Fairing for Counter {
 ///     fn info(&self) -> Info {
 ///         Info {
@@ -228,33 +266,29 @@ pub use self::info_kind::{Info, Kind};
 ///         }
 ///     }
 ///
-///     fn on_request<'a>(&'a self, request: &'a mut Request, _: &'a Data) -> Pin<Box<dyn Future<Output=()> + Send + 'a>> {
+///     async fn on_request<'a>(&'a self, req: &'a mut Request<'_>, _: &'a Data) {
-///         Box::pin(async move {
+///         if req.method() == Method::Get {
-///             if request.method() == Method::Get {
 ///             self.get.fetch_add(1, Ordering::Relaxed);
-///             } else if request.method() == Method::Post {
+///         } else if req.method() == Method::Post {
 ///             self.post.fetch_add(1, Ordering::Relaxed);
 ///         }
-///         })
 ///     }
 ///
-///     fn on_response<'a>(&'a self, request: &'a Request<'_>, response: &'a mut Response<'_>) -> Pin<Box<dyn Future<Output=()> + Send + 'a>> {
+///     async fn on_response<'a>(&'a self, req: &'a Request<'_>, res: &'a mut Response<'_>) {
-///         Box::pin(async move {
 ///         // Don't change a successful user's response, ever.
-///             if response.status() != Status::NotFound {
+///         if res.status() != Status::NotFound {
 ///             return
 ///         }
 ///
-///             if request.method() == Method::Get && request.uri().path() == "/counts" {
+///         if req.method() == Method::Get && req.uri().path() == "/counts" {
 ///             let get_count = self.get.load(Ordering::Relaxed);
 ///             let post_count = self.post.load(Ordering::Relaxed);
 ///
 ///             let body = format!("Get: {}\nPost: {}", get_count, post_count);
-///                 response.set_status(Status::Ok);
+///             res.set_status(Status::Ok);
-///                 response.set_header(ContentType::Plain);
+///             res.set_header(ContentType::Plain);
-///                 response.set_sized_body(Cursor::new(body));
+///             res.set_sized_body(Cursor::new(body));
 ///         }
-///         })
 ///     }
 /// }
 /// ```
@@ -286,6 +320,7 @@ pub use self::info_kind::{Info, Kind};
 /// #[derive(Copy, Clone)]
 /// struct TimerStart(Option<SystemTime>);
 ///
+/// #[rocket::async_trait]
 /// impl Fairing for RequestTimer {
 ///     fn info(&self) -> Info {
 ///         Info {
@@ -295,25 +330,21 @@ pub use self::info_kind::{Info, Kind};
 ///     }
 ///
 ///     /// Stores the start time of the request in request-local state.
-///     fn on_request<'a>(&'a self, request: &'a mut Request, _: &'a Data) -> Pin<Box<dyn Future<Output=()> + Send + 'a>> {
+///     async fn on_request<'a>(&'a self, request: &'a mut Request<'_>, _: &'a Data) {
-///         Box::pin(async move {
 ///         // Store a `TimerStart` instead of directly storing a `SystemTime`
 ///         // to ensure that this usage doesn't conflict with anything else
 ///         // that might store a `SystemTime` in request-local cache.
 ///         request.local_cache(|| TimerStart(Some(SystemTime::now())));
-///         })
 ///     }
 ///
 ///     /// Adds a header to the response indicating how long the server took to
 ///     /// process the request.
-///     fn on_response<'a>(&'a self, request: &'a Request<'_>, response: &'a mut Response<'_>) -> Pin<Box<dyn Future<Output=()> + Send + 'a>> {
+///     async fn on_response<'a>(&'a self, req: &'a Request<'_>, res: &'a mut Response<'_>) {
-///         Box::pin(async move {
+///         let start_time = req.local_cache(|| TimerStart(None));
-///             let start_time = request.local_cache(|| TimerStart(None));
 ///         if let Some(Ok(duration)) = start_time.0.map(|st| st.elapsed()) {
 ///             let ms = duration.as_secs() * 1000 + duration.subsec_millis() as u64;
-///                 response.set_raw_header("X-Response-Time", format!("{} ms", ms));
+///             res.set_raw_header("X-Response-Time", format!("{} ms", ms));
 ///         }
-///         })
 ///     }
 /// }
 ///
@@ -336,6 +367,7 @@ pub use self::info_kind::{Info, Kind};
 ///
 /// [request-local state]: https://rocket.rs/v0.5/guide/state/#request-local-state
 
+#[crate::async_trait]
 pub trait Fairing: Send + Sync + 'static {
     /// Returns an [`Info`] structure containing the `name` and [`Kind`] of this
     /// fairing. The `name` can be any arbitrary string. `Kind` must be an `or`d
@@ -409,9 +441,7 @@ pub trait Fairing: Send + Sync + 'static {
     ///
     /// The default implementation of this method does nothing.
     #[allow(unused_variables)]
-    fn on_request<'a>(&'a self, request: &'a mut Request<'_>, data: &'a Data) -> BoxFuture<'a, ()> {
+    async fn on_request<'a>(&'a self, req: &'a mut Request<'_>, data: &'a Data) {}
-        Box::pin(async { })
-    }
 
     /// The response callback.
     ///
@@ -424,11 +454,10 @@ pub trait Fairing: Send + Sync + 'static {
     ///
     /// The default implementation of this method does nothing.
     #[allow(unused_variables)]
-    fn on_response<'a>(&'a self, request: &'a Request<'_>, response: &'a mut Response<'_>) -> BoxFuture<'a, ()> {
+    async fn on_response<'a>(&'a self, req: &'a Request<'_>, res: &'a mut Response<'_>) {}
-        Box::pin(async { })
-    }
 }
 
+#[crate::async_trait]
 impl<T: Fairing> Fairing for std::sync::Arc<T> {
     #[inline]
     fn info(&self) -> Info {
@@ -446,12 +475,12 @@ impl<T: Fairing> Fairing for std::sync::Arc<T> {
     }
 
     #[inline]
-    fn on_request<'a>(&'a self, request: &'a mut Request<'_>, data: &'a Data) -> BoxFuture<'a, ()> {
+    async fn on_request<'a>(&'a self, req: &'a mut Request<'_>, data: &'a Data) {
-        (self as &T).on_request(request, data)
+        (self as &T).on_request(req, data).await;
     }
 
     #[inline]
-    fn on_response<'a>(&'a self, request: &'a Request<'_>, response: &'a mut Response<'_>) -> BoxFuture<'a, ()> {
+    async fn on_response<'a>(&'a self, req: &'a Request<'_>, res: &'a mut Response<'_>) {
-        (self as &T).on_response(request, response)
+        (self as &T).on_response(req, res).await;
     }
 }

core/lib/src/lib.rs

@@ -94,6 +94,7 @@
 
 #[allow(unused_imports)] #[macro_use] extern crate rocket_codegen;
 pub use rocket_codegen::*;
+pub use async_trait::*;
 
 #[macro_use] extern crate log;
 #[macro_use] extern crate pear;

examples/fairings/src/main.rs

@@ -19,6 +19,7 @@ struct Counter {
     post: AtomicUsize,
 }
 
+#[rocket::async_trait]
 impl Fairing for Counter {
     fn info(&self) -> Info {
         Info {
@@ -27,36 +28,28 @@ impl Fairing for Counter {
         }
     }
 
-    fn on_request<'a>(&'a self, request: &'a mut Request<'_>, _: &'a Data)
+    async fn on_request<'a>(&'a self, request: &'a mut Request<'_>, _: &'a Data) {
-        -> std::pin::Pin<Box<dyn std::future::Future<Output=()> + Send + 'a>>
-    {
-        Box::pin(async move {
         if request.method() == Method::Get {
             self.get.fetch_add(1, Ordering::Relaxed);
         } else if request.method() == Method::Post {
             self.post.fetch_add(1, Ordering::Relaxed);
         }
-        })
     }
 
-    fn on_response<'a>(&'a self, request: &'a Request<'_>, response: &'a mut Response<'_>)
+    async fn on_response<'a>(&'a self, req: &'a Request<'_>, res: &'a mut Response<'_>) {
-        -> std::pin::Pin<Box<dyn std::future::Future<Output=()> + Send + 'a>>
+        if res.status() != Status::NotFound {
-    {
-        Box::pin(async move {
-            if response.status() != Status::NotFound {
             return
         }
 
-            if request.method() == Method::Get && request.uri().path() == "/counts" {
+        if req.method() == Method::Get && req.uri().path() == "/counts" {
             let get_count = self.get.load(Ordering::Relaxed);
             let post_count = self.post.load(Ordering::Relaxed);
 
             let body = format!("Get: {}\nPost: {}", get_count, post_count);
-                response.set_status(Status::Ok);
+            res.set_status(Status::Ok);
-                response.set_header(ContentType::Plain);
+            res.set_header(ContentType::Plain);
-                response.set_sized_body(Cursor::new(body)).await;
+            res.set_sized_body(Cursor::new(body)).await;
         }
-        })
     }
 }