check point

axum/src/extract/matched_path.rs

@@ -149,7 +149,7 @@ mod tests {
                 "/public",
                 Router::new().route("/assets/*path", get(handler)),
             )
-            .nest_service("/foo", handler.into_service())
+            .nest_service("/foo", handler.into_service(()))
             .layer(tower::layer::layer_fn(SetMatchedPathExtension))
             .state(());
 

axum/src/handler/into_extension_service.rs

@@ -0,0 +1,67 @@
+use super::Handler;
+use crate::response::Response;
+use http::Request;
+use std::{
+    convert::Infallible,
+    marker::PhantomData,
+    task::{Context, Poll},
+};
+use tower_service::Service;
+
+/// A `Handler` converted into a `Service` that reads the state from request extensions. Panics if
+/// the state is missing.
+pub(crate) struct IntoExtensionService<H, S, T, B> {
+    handler: H,
+    _marker: PhantomData<fn() -> (S, T, B)>,
+}
+
+impl<H, S, T, B> IntoExtensionService<H, S, T, B> {
+    pub(crate) fn new(handler: H) -> Self {
+        Self {
+            handler,
+            _marker: PhantomData,
+        }
+    }
+}
+
+impl<H, S, T, B> Clone for IntoExtensionService<H, S, T, B>
+where
+    H: Clone,
+{
+    fn clone(&self) -> Self {
+        Self {
+            handler: self.handler.clone(),
+            _marker: PhantomData,
+        }
+    }
+}
+
+impl<H, S, T, B> Service<Request<B>> for IntoExtensionService<H, S, T, B>
+where
+    H: Handler<S, T, B> + Clone + Send + 'static,
+    B: Send + 'static,
+    S: Clone + Send + Sync + 'static,
+{
+    type Response = Response;
+    type Error = Infallible;
+    type Future = super::future::IntoServiceFuture<H::Future>;
+
+    #[inline]
+    fn poll_ready(&mut self, _cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
+        // `IntoService` can only be constructed from async functions which are always ready, or
+        // from `Layered` which bufferes in `<Layered as Handler>::call` and is therefore
+        // also always ready.
+        Poll::Ready(Ok(()))
+    }
+
+    fn call(&mut self, req: Request<B>) -> Self::Future {
+        use futures_util::future::FutureExt;
+
+        let handler = self.handler.clone();
+        let state = req.extensions().get::<S>().unwrap().clone();
+        let future = Handler::call(handler, state, req);
+        let future = future.map(Ok as _);
+
+        super::future::IntoServiceFuture::new(future)
+    }
+}

axum/src/handler/into_service.rs

@@ -18,13 +18,6 @@ pub struct IntoService<H, S, T, B> {
     _marker: PhantomData<fn() -> (T, B)>,
 }
 
-#[test]
-fn traits() {
-    use crate::test_helpers::*;
-    assert_send::<IntoService<(), (), NotSendSync, NotSendSync>>();
-    assert_sync::<IntoService<(), (), NotSendSync, NotSendSync>>();
-}
-
 impl<H, S, T, B> IntoService<H, S, T, B> {
     pub(super) fn new(handler: H, state: S) -> Self {
         Self {
@@ -89,3 +82,10 @@ where
         super::future::IntoServiceFuture::new(future)
     }
 }
+
+#[test]
+fn traits() {
+    use crate::test_helpers::*;
+    assert_send::<IntoService<(), (), NotSendSync, NotSendSync>>();
+    assert_sync::<IntoService<(), (), NotSendSync, NotSendSync>>();
+}

axum/src/handler/mod.rs

@@ -43,16 +43,19 @@ use crate::{
     BoxError,
 };
 use http::Request;
-use std::{fmt, future::Future, marker::PhantomData, pin::Pin};
+use std::{convert::Infallible, fmt, future::Future, marker::PhantomData, pin::Pin};
 use tower::ServiceExt;
 use tower_layer::Layer;
 use tower_service::Service;
 
-pub mod future;
+mod into_extension_service;
 mod into_service;
 
+pub(crate) use self::into_extension_service::IntoExtensionService;
 pub use self::into_service::IntoService;
 
+pub mod future;
+
 /// Trait for async functions that can be used to handle requests.
 ///
 /// You shouldn't need to depend on this trait directly. It is automatically
@@ -61,7 +64,8 @@ pub use self::into_service::IntoService;
 /// See the [module docs](crate::handler) for more details.
 ///
 #[doc = include_str!("../docs/debugging_handler_type_errors.md")]
-pub trait Handler<S, T, B = Body>: Clone + Send + Sized + 'static {
+// TODO(david): Add back `B = Body` default
+pub trait Handler<S, T, B>: Clone + Send + Sized + 'static {
     /// The type of future calling this handler returns.
     type Future: Future<Output = Response> + Send + 'static;
 
@@ -104,13 +108,15 @@ pub trait Handler<S, T, B = Body>: Clone + Send + Sized + 'static {
     /// # axum::Server::bind(&"".parse().unwrap()).serve(app.into_make_service()).await.unwrap();
     /// # };
     /// ```
-    fn layer<L>(self, layer: L) -> Layered<L::Service, T>
+    fn layer<L>(self, layer: L) -> Layered<Self, S, B, L>
     where
         L: Layer<IntoService<Self, S, T, B>>,
     {
-        // TODO(david): write this, somehow
+        Layered {
-        todo!()
+            handler: self,
-        // Layered::new(layer.layer(self.into_service()))
+            layer,
+            _marker: PhantomData,
+        }
     }
 
     /// Convert the handler into a [`Service`].
@@ -145,6 +151,7 @@ pub trait Handler<S, T, B = Body>: Clone + Send + Sized + 'static {
     /// ```
     ///
     /// [`Router::fallback`]: crate::routing::Router::fallback
+    // TODO(david): remove this
     fn into_service(self, state: S) -> IntoService<Self, S, T, B> {
         IntoService::new(self, state)
     }
@@ -172,6 +179,7 @@ pub trait Handler<S, T, B = Body>: Clone + Send + Sized + 'static {
     /// ```
     ///
     /// [`MakeService`]: tower::make::MakeService
+    // TODO(david): remove this
     fn into_make_service(self, state: S) -> IntoMakeService<IntoService<Self, S, T, B>> {
         IntoMakeService::new(self.into_service(state))
     }
@@ -204,6 +212,7 @@ pub trait Handler<S, T, B = Body>: Clone + Send + Sized + 'static {
     ///
     /// [`MakeService`]: tower::make::MakeService
     /// [`Router::into_make_service_with_connect_info`]: crate::routing::Router::into_make_service_with_connect_info
+    // TODO(david): remove this
     fn into_make_service_with_connect_info<C>(
         self,
         state: S,
@@ -264,63 +273,79 @@ all_the_tuples!(impl_handler);
 /// A [`Service`] created from a [`Handler`] by applying a Tower middleware.
 ///
 /// Created with [`Handler::layer`]. See that method for more details.
-pub struct Layered<S, T> {
+pub struct Layered<H, S, B, L> {
-    svc: S,
+    handler: H,
-    _input: PhantomData<fn() -> T>,
+    layer: L,
+    _marker: PhantomData<(S, B)>,
 }
 
-impl<S, T> fmt::Debug for Layered<S, T>
+impl<H, S, B, L> Clone for Layered<H, S, B, L>
 where
-    S: fmt::Debug,
+    H: Clone,
-{
+    L: Clone,
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        f.debug_struct("Layered").field("svc", &self.svc).finish()
-    }
-}
-
-impl<S, T> Clone for Layered<S, T>
-where
-    S: Clone,
 {
     fn clone(&self) -> Self {
-        Self::new(self.svc.clone())
+        Self {
+            handler: self.handler.clone(),
+            layer: self.layer.clone(),
+            _marker: self._marker,
+        }
     }
 }
 
-impl<S, T, ReqBody, ResBody, St> Handler<St, T, ReqBody> for Layered<S, T>
+impl<H, S, B, L> Copy for Layered<H, S, B, L>
 where
-    S: Service<Request<ReqBody>, Response = Response<ResBody>> + Clone + Send + 'static,
+    H: Copy,
-    S::Error: IntoResponse,
+    L: Copy,
-    S::Future: Send,
+{
-    T: 'static,
+}
-    ReqBody: Send + 'static,
+
+impl<H, S, B, L> fmt::Debug for Layered<H, S, B, L>
+where
+    L: fmt::Debug,
+{
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let Self {
+            handler: _,
+            layer,
+            _marker,
+        } = self;
+        f.debug_struct("Layered").field("layer", &layer).finish()
+    }
+}
+
+impl<H, L, S, T, B, ResBody> Handler<S, T, B> for Layered<H, S, B, L>
+where
+    H: Handler<S, T, B> + Clone + Send + 'static,
+    S: Send + 'static,
+    L: Layer<IntoService<H, S, T, B>> + Clone + Send + 'static,
+    L::Service: Service<Request<B>, Response = Response<ResBody>, Error = Infallible>
+        + Clone
+        + Send
+        + 'static,
+    <L::Service as Service<Request<B>>>::Future: Send,
+    B: Send + 'static,
     ResBody: HttpBody<Data = Bytes> + Send + 'static,
     ResBody::Error: Into<BoxError>,
 {
-    type Future = future::LayeredFuture<S, ReqBody>;
+    type Future = future::LayeredFuture<L::Service, B>;
 
-    fn call(self, state: St, req: Request<ReqBody>) -> Self::Future {
+    fn call(self, state: S, req: Request<B>) -> Self::Future {
         use futures_util::future::{FutureExt, Map};
 
-        let future: Map<_, fn(Result<S::Response, S::Error>) -> _> =
+        let svc = self.handler.into_service(state);
-            self.svc.oneshot(req).map(|result| match result {
+        let svc = self.layer.layer(svc);
+
+        let future: Map<_, fn(Result<Response<ResBody>, Infallible>) -> _> =
+            svc.oneshot(req).map(|result| match result {
                 Ok(res) => res.map(boxed),
-                Err(res) => res.into_response(),
+                Err(err) => match err {},
             });
 
         future::LayeredFuture::new(future)
     }
 }
 
-impl<S, T> Layered<S, T> {
-    pub(crate) fn new(svc: S) -> Self {
-        Self {
-            svc,
-            _input: PhantomData,
-        }
-    }
-}
-
 #[cfg(test)]
 mod tests {
     use super::*;

axum/src/routing/method_routing.rs

@@ -1,9 +1,9 @@
-use super::IntoMakeService;
+use super::{IntoMakeService, MissingState, WithState};
 use crate::{
     body::{boxed, Body, Bytes, Empty, HttpBody},
     error_handling::{HandleError, HandleErrorLayer},
-    extract::connect_info::IntoMakeServiceWithConnectInfo,
+    extract::{connect_info::IntoMakeServiceWithConnectInfo, State},
-    handler::Handler,
+    handler::{Handler, IntoExtensionService},
     http::{Method, Request, StatusCode},
     response::Response,
     routing::{future::RouteFuture, Fallback, MethodFilter, Route},
@@ -76,10 +76,10 @@ macro_rules! top_level_service_fn {
         $name:ident, $method:ident
     ) => {
         $(#[$m])+
-        pub fn $name<S, ReqBody, ResBody>(svc: S) -> MethodRouter<ReqBody, S::Error>
+        pub fn $name<T, ReqBody, ResBody, S>(svc: T) -> MethodRouter<S, ReqBody, T::Error, MissingState>
         where
-            S: Service<Request<ReqBody>, Response = Response<ResBody>> + Clone + Send + 'static,
+            T: Service<Request<ReqBody>, Response = Response<ResBody>> + Clone + Send + 'static,
-            S::Future: Send + 'static,
+            T::Future: Send + 'static,
             ResBody: HttpBody<Data = Bytes> + Send + 'static,
             ResBody::Error: Into<BoxError>,
         {
@@ -137,11 +137,12 @@ macro_rules! top_level_handler_fn {
         $name:ident, $method:ident
     ) => {
         $(#[$m])+
-        pub fn $name<H, T, B>(handler: H) -> MethodRouter<B, Infallible>
+        pub fn $name<H, S, T, B>(handler: H) -> MethodRouter<S, B, Infallible, MissingState>
         where
-            H: Handler<T, B>,
+            H: Handler<S, T, B>,
             B: Send + 'static,
             T: 'static,
+            S: Clone + Send + Sync + 'static,
         {
             on(MethodFilter::$method, handler)
         }
@@ -208,13 +209,13 @@ macro_rules! chained_service_fn {
         $name:ident, $method:ident
     ) => {
         $(#[$m])+
-        pub fn $name<S, ResBody>(self, svc: S) -> Self
+        pub fn $name<T, ResBody>(self, svc: T) -> Self
         where
-            S: Service<Request<ReqBody>, Response = Response<ResBody>, Error = E>
+            T: Service<Request<B>, Response = Response<ResBody>, Error = E>
                 + Clone
                 + Send
                 + 'static,
-            S::Future: Send + 'static,
+            T::Future: Send + 'static,
             ResBody: HttpBody<Data = Bytes> + Send + 'static,
             ResBody::Error: Into<BoxError>,
         {
@@ -274,8 +275,9 @@ macro_rules! chained_handler_fn {
         $(#[$m])+
         pub fn $name<H, T>(self, handler: H) -> Self
         where
-            H: Handler<T, B>,
+            H: Handler<S, T, B>,
             T: 'static,
+            S: Clone + Send + Sync + 'static,
         {
             self.on(MethodFilter::$method, handler)
         }
@@ -316,13 +318,13 @@ top_level_service_fn!(trace_service, TRACE);
 /// # axum::Server::bind(&"".parse().unwrap()).serve(app.into_make_service()).await.unwrap();
 /// # };
 /// ```
-pub fn on_service<S, ReqBody, ResBody>(
+pub fn on_service<T, ReqBody, ResBody, S>(
     filter: MethodFilter,
-    svc: S,
+    svc: T,
-) -> MethodRouter<ReqBody, S::Error>
+) -> MethodRouter<S, ReqBody, T::Error, MissingState>
 where
-    S: Service<Request<ReqBody>, Response = Response<ResBody>> + Clone + Send + 'static,
+    T: Service<Request<ReqBody>, Response = Response<ResBody>> + Clone + Send + 'static,
-    S::Future: Send + 'static,
+    T::Future: Send + 'static,
     ResBody: HttpBody<Data = Bytes> + Send + 'static,
     ResBody::Error: Into<BoxError>,
 {
@@ -382,14 +384,18 @@ where
 /// # axum::Server::bind(&"".parse().unwrap()).serve(app.into_make_service()).await.unwrap();
 /// # };
 /// ```
-pub fn any_service<S, ReqBody, ResBody>(svc: S) -> MethodRouter<ReqBody, S::Error>
+pub fn any_service<T, ReqBody, ResBody, S>(
+    svc: T,
+) -> MethodRouter<S, ReqBody, T::Error, MissingState>
 where
-    S: Service<Request<ReqBody>, Response = Response<ResBody>> + Clone + Send + 'static,
+    T: Service<Request<ReqBody>, Response = Response<ResBody>> + Clone + Send + 'static,
-    S::Future: Send + 'static,
+    T::Future: Send + 'static,
     ResBody: HttpBody<Data = Bytes> + Send + 'static,
     ResBody::Error: Into<BoxError>,
 {
-    MethodRouter::new().fallback(svc).skip_allow_header()
+    MethodRouter::new()
+        .fallback_service(svc)
+        .skip_allow_header()
 }
 
 top_level_handler_fn!(delete, DELETE);
@@ -420,11 +426,15 @@ top_level_handler_fn!(trace, TRACE);
 /// # axum::Server::bind(&"".parse().unwrap()).serve(app.into_make_service()).await.unwrap();
 /// # };
 /// ```
-pub fn on<H, T, B>(filter: MethodFilter, handler: H) -> MethodRouter<B, Infallible>
+pub fn on<H, S, T, B>(
+    filter: MethodFilter,
+    handler: H,
+) -> MethodRouter<S, B, Infallible, MissingState>
 where
-    H: Handler<T, B>,
+    H: Handler<S, T, B>,
     B: Send + 'static,
     T: 'static,
+    S: Clone + Send + Sync + 'static,
 {
     MethodRouter::new().on(filter, handler)
 }
@@ -466,20 +476,26 @@ where
 /// # axum::Server::bind(&"".parse().unwrap()).serve(app.into_make_service()).await.unwrap();
 /// # };
 /// ```
-pub fn any<H, T, B>(handler: H) -> MethodRouter<B, Infallible>
+pub fn any<H, S, T, B>(handler: H) -> MethodRouter<S, B, Infallible, MissingState>
 where
-    H: Handler<T, B>,
+    H: Handler<S, T, B>,
     B: Send + 'static,
     T: 'static,
+    S: Clone + Send + Sync + 'static,
 {
     MethodRouter::new()
-        .fallback_boxed_response_body(handler.into_service())
+        .fallback_boxed_response_body(IntoExtensionService::new(handler))
         .skip_allow_header()
 }
 
 /// A [`Service`] that accepts requests based on a [`MethodFilter`] and
 /// allows chaining additional handlers and services.
-pub struct MethodRouter<B = Body, E = Infallible> {
+// TODO(david): Bring back `B = Body, E = Infallible` defaults
+pub struct MethodRouter<S, B, E, R> {
+    // Invariant: If `R == MissingState` then `state` is `None`
+    // If `R == WithState` then state is `Some`
+    // `R` cannot have other values
+    state: Option<S>,
     get: Option<Route<B, E>>,
     head: Option<Route<B, E>>,
     delete: Option<Route<B, E>>,
@@ -490,7 +506,7 @@ pub struct MethodRouter<B = Body, E = Infallible> {
     trace: Option<Route<B, E>>,
     fallback: Fallback<B, E>,
     allow_header: AllowHeader,
-    _request_body: PhantomData<fn() -> (B, E)>,
+    _marker: PhantomData<R>,
 }
 
 #[derive(Clone)]
@@ -503,9 +519,13 @@ enum AllowHeader {
     Bytes(BytesMut),
 }
 
-impl<B, E> fmt::Debug for MethodRouter<B, E> {
+impl<S, B, E, R> fmt::Debug for MethodRouter<S, B, E, R>
+where
+    S: fmt::Debug,
+{
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_struct("MethodRouter")
+            .field("state", &self.state)
             .field("get", &self.get)
             .field("head", &self.head)
             .field("delete", &self.delete)
@@ -519,7 +539,7 @@ impl<B, E> fmt::Debug for MethodRouter<B, E> {
     }
 }
 
-impl<B, E> MethodRouter<B, E> {
+impl<S, B, E> MethodRouter<S, B, E, MissingState> {
     /// Create a default `MethodRouter` that will respond with `405 Method Not Allowed` to all
     /// requests.
     pub fn new() -> Self {
@@ -530,6 +550,7 @@ impl<B, E> MethodRouter<B, E> {
         }));
 
         Self {
+            state: None,
             get: None,
             head: None,
             delete: None,
@@ -540,14 +561,47 @@ impl<B, E> MethodRouter<B, E> {
             trace: None,
             allow_header: AllowHeader::None,
             fallback: Fallback::Default(fallback),
-            _request_body: PhantomData,
+            _marker: PhantomData,
+        }
+    }
+
+    /// TODO(david): docs
+    pub fn state(self, state: S) -> MethodRouter<S, B, E, WithState> {
+        MethodRouter {
+            state: Some(state),
+            get: self.get,
+            head: self.head,
+            delete: self.delete,
+            options: self.options,
+            patch: self.patch,
+            post: self.post,
+            put: self.put,
+            trace: self.trace,
+            fallback: self.fallback,
+            allow_header: self.allow_header,
+            _marker: PhantomData,
         }
     }
 }
 
-impl<B> MethodRouter<B, Infallible>
+impl<S, B, E> MethodRouter<S, B, E, WithState> {
+    /// TODO(david): docs
+    pub fn with_state(state: S) -> Self {
+        MethodRouter::new().state(state)
+    }
+}
+
+impl<B, E> MethodRouter<(), B, E, WithState> {
+    /// TODO(david): docs
+    pub fn without_state() -> Self {
+        MethodRouter::with_state(())
+    }
+}
+
+impl<S, B, R> MethodRouter<S, B, Infallible, R>
 where
     B: Send + 'static,
+    S: Clone + Send + Sync + 'static,
 {
     /// Chain an additional handler that will accept requests matching the given
     /// `MethodFilter`.
@@ -574,10 +628,10 @@ where
     /// ```
     pub fn on<H, T>(self, filter: MethodFilter, handler: H) -> Self
     where
-        H: Handler<T, B>,
+        H: Handler<S, T, B>,
         T: 'static,
     {
-        self.on_service_boxed_response_body(filter, handler.into_service())
+        self.on_service_boxed_response_body(filter, IntoExtensionService::new(handler))
     }
 
     chained_handler_fn!(delete, DELETE);
@@ -589,6 +643,22 @@ where
     chained_handler_fn!(put, PUT);
     chained_handler_fn!(trace, TRACE);
 
+    #[doc = include_str!("../docs/routing/fallback.md")]
+    pub fn fallback<H, T>(mut self, handler: H) -> Self
+    where
+        H: Handler<S, T, B>,
+        T: 'static,
+        S: Clone + Send + Sync + 'static,
+    {
+        self.fallback_boxed_response_body(IntoExtensionService::new(handler))
+    }
+}
+
+impl<S, B> MethodRouter<S, B, Infallible, WithState>
+where
+    B: Send + 'static,
+    S: Clone + Send + Sync + 'static,
+{
     /// Convert the handler into a [`MakeService`].
     ///
     /// This allows you to serve a single handler if you don't need any routing:
@@ -658,7 +728,7 @@ where
     }
 }
 
-impl<ReqBody, E> MethodRouter<ReqBody, E> {
+impl<S, B, E, R> MethodRouter<S, B, E, R> {
     /// Chain an additional service that will accept requests matching the given
     /// `MethodFilter`.
     ///
@@ -684,13 +754,10 @@ impl<ReqBody, E> MethodRouter<ReqBody, E> {
     /// # axum::Server::bind(&"".parse().unwrap()).serve(app.into_make_service()).await.unwrap();
     /// # };
     /// ```
-    pub fn on_service<S, ResBody>(self, filter: MethodFilter, svc: S) -> Self
+    pub fn on_service<T, ResBody>(self, filter: MethodFilter, svc: T) -> Self
     where
-        S: Service<Request<ReqBody>, Response = Response<ResBody>, Error = E>
+        T: Service<Request<B>, Response = Response<ResBody>, Error = E> + Clone + Send + 'static,
-            + Clone
+        T::Future: Send + 'static,
-            + Send
-            + 'static,
-        S::Future: Send + 'static,
         ResBody: HttpBody<Data = Bytes> + Send + 'static,
         ResBody::Error: Into<BoxError>,
     {
@@ -707,13 +774,10 @@ impl<ReqBody, E> MethodRouter<ReqBody, E> {
     chained_service_fn!(trace_service, TRACE);
 
     #[doc = include_str!("../docs/method_routing/fallback.md")]
-    pub fn fallback<S, ResBody>(mut self, svc: S) -> Self
+    pub fn fallback_service<T, ResBody>(mut self, svc: T) -> Self
     where
-        S: Service<Request<ReqBody>, Response = Response<ResBody>, Error = E>
+        T: Service<Request<B>, Response = Response<ResBody>, Error = E> + Clone + Send + 'static,
-            + Clone
+        T::Future: Send + 'static,
-            + Send
-            + 'static,
-        S::Future: Send + 'static,
         ResBody: HttpBody<Data = Bytes> + Send + 'static,
         ResBody::Error: Into<BoxError>,
     {
@@ -721,10 +785,10 @@ impl<ReqBody, E> MethodRouter<ReqBody, E> {
         self
     }
 
-    fn fallback_boxed_response_body<S>(mut self, svc: S) -> Self
+    fn fallback_boxed_response_body<T>(mut self, svc: T) -> Self
     where
-        S: Service<Request<ReqBody>, Response = Response, Error = E> + Clone + Send + 'static,
+        T: Service<Request<B>, Response = Response, Error = E> + Clone + Send + 'static,
-        S::Future: Send + 'static,
+        T::Future: Send + 'static,
     {
         self.fallback = Fallback::Custom(Route::new(svc));
         self
@@ -734,9 +798,9 @@ impl<ReqBody, E> MethodRouter<ReqBody, E> {
     pub fn layer<L, NewReqBody, NewResBody, NewError>(
         self,
         layer: L,
-    ) -> MethodRouter<NewReqBody, NewError>
+    ) -> MethodRouter<S, NewReqBody, NewError, R>
     where
-        L: Layer<Route<ReqBody, E>>,
+        L: Layer<Route<B, E>>,
         L::Service: Service<Request<NewReqBody>, Response = Response<NewResBody>, Error = NewError>
             + Clone
             + Send
@@ -753,6 +817,7 @@ impl<ReqBody, E> MethodRouter<ReqBody, E> {
         let layer_fn = |s| layer.layer(s);
 
         MethodRouter {
+            state: self.state,
             get: self.get.map(layer_fn),
             head: self.head.map(layer_fn),
             delete: self.delete.map(layer_fn),
@@ -763,19 +828,19 @@ impl<ReqBody, E> MethodRouter<ReqBody, E> {
             trace: self.trace.map(layer_fn),
             fallback: self.fallback.map(layer_fn),
             allow_header: self.allow_header,
-            _request_body: PhantomData,
+            _marker: self._marker,
         }
     }
 
     #[doc = include_str!("../docs/method_routing/route_layer.md")]
-    pub fn route_layer<L, NewResBody>(self, layer: L) -> MethodRouter<ReqBody, E>
+    pub fn route_layer<L, NewResBody>(self, layer: L) -> MethodRouter<S, B, E, R>
     where
-        L: Layer<Route<ReqBody, E>>,
+        L: Layer<Route<B, E>>,
-        L::Service: Service<Request<ReqBody>, Response = Response<NewResBody>, Error = E>
+        L::Service: Service<Request<B>, Response = Response<NewResBody>, Error = E>
             + Clone
             + Send
             + 'static,
-        <L::Service as Service<Request<ReqBody>>>::Future: Send + 'static,
+        <L::Service as Service<Request<B>>>::Future: Send + 'static,
         NewResBody: HttpBody<Data = Bytes> + Send + 'static,
         NewResBody::Error: Into<BoxError>,
     {
@@ -787,6 +852,7 @@ impl<ReqBody, E> MethodRouter<ReqBody, E> {
         let layer_fn = |s| layer.layer(s);
 
         MethodRouter {
+            state: self.state,
             get: self.get.map(layer_fn),
             head: self.head.map(layer_fn),
             delete: self.delete.map(layer_fn),
@@ -797,12 +863,12 @@ impl<ReqBody, E> MethodRouter<ReqBody, E> {
             trace: self.trace.map(layer_fn),
             fallback: self.fallback,
             allow_header: self.allow_header,
-            _request_body: PhantomData,
+            _marker: self._marker,
         }
     }
 
     #[doc = include_str!("../docs/method_routing/merge.md")]
-    pub fn merge(self, other: MethodRouter<ReqBody, E>) -> Self {
+    pub fn merge(self, other: MethodRouter<S, B, E, MissingState>) -> Self {
         macro_rules! merge {
             ( $first:ident, $second:ident ) => {
                 match ($first, $second) {
@@ -819,6 +885,7 @@ impl<ReqBody, E> MethodRouter<ReqBody, E> {
         }
 
         let Self {
+            state,
             get,
             head,
             delete,
@@ -829,10 +896,11 @@ impl<ReqBody, E> MethodRouter<ReqBody, E> {
             trace,
             fallback,
             allow_header,
-            _request_body: _,
+            _marker: _,
         } = self;
 
-        let Self {
+        let MethodRouter {
+            state: state_other,
             get: get_other,
             head: head_other,
             delete: delete_other,
@@ -843,8 +911,9 @@ impl<ReqBody, E> MethodRouter<ReqBody, E> {
             trace: trace_other,
             fallback: fallback_other,
             allow_header: allow_header_other,
-            _request_body: _,
+            _marker: _,
         } = other;
+        debug_assert!(state_other.is_none());
 
         let get = merge!(get, get_other);
         let head = merge!(head, head_other);
@@ -877,6 +946,7 @@ impl<ReqBody, E> MethodRouter<ReqBody, E> {
         };
 
         Self {
+            state,
             get,
             head,
             delete,
@@ -887,30 +957,30 @@ impl<ReqBody, E> MethodRouter<ReqBody, E> {
             trace,
             fallback,
             allow_header,
-            _request_body: PhantomData,
+            _marker: PhantomData,
         }
     }
 
     /// Apply a [`HandleErrorLayer`].
     ///
     /// This is a convenience method for doing `self.layer(HandleErrorLayer::new(f))`.
-    pub fn handle_error<F, T>(self, f: F) -> MethodRouter<ReqBody, Infallible>
+    pub fn handle_error<F, T>(self, f: F) -> MethodRouter<S, B, Infallible, R>
     where
         F: Clone + Send + 'static,
-        HandleError<Route<ReqBody, E>, F, T>:
+        HandleError<Route<B, E>, F, T>:
-            Service<Request<ReqBody>, Response = Response, Error = Infallible>,
+            Service<Request<B>, Response = Response, Error = Infallible>,
-        <HandleError<Route<ReqBody, E>, F, T> as Service<Request<ReqBody>>>::Future: Send,
+        <HandleError<Route<B, E>, F, T> as Service<Request<B>>>::Future: Send,
         T: 'static,
         E: 'static,
-        ReqBody: 'static,
+        B: 'static,
     {
         self.layer(HandleErrorLayer::new(f))
     }
 
-    fn on_service_boxed_response_body<S>(self, filter: MethodFilter, svc: S) -> Self
+    fn on_service_boxed_response_body<T>(self, filter: MethodFilter, svc: T) -> Self
     where
-        S: Service<Request<ReqBody>, Response = Response, Error = E> + Clone + Send + 'static,
+        T: Service<Request<B>, Response = Response, Error = E> + Clone + Send + 'static,
-        S::Future: Send + 'static,
+        T::Future: Send + 'static,
     {
         macro_rules! set_service {
             (
@@ -940,6 +1010,7 @@ impl<ReqBody, E> MethodRouter<ReqBody, E> {
 
         // written with a pattern match like this to ensure we update all fields
         let Self {
+            state,
             mut get,
             mut head,
             mut delete,
@@ -950,7 +1021,7 @@ impl<ReqBody, E> MethodRouter<ReqBody, E> {
             mut trace,
             fallback,
             mut allow_header,
-            _request_body: _,
+            _marker,
         } = self;
         let svc = Some(Route::new(svc));
         set_service!(
@@ -969,6 +1040,7 @@ impl<ReqBody, E> MethodRouter<ReqBody, E> {
             ]
         );
         Self {
+            state,
             get,
             head,
             delete,
@@ -979,7 +1051,7 @@ impl<ReqBody, E> MethodRouter<ReqBody, E> {
             trace,
             fallback,
             allow_header,
-            _request_body: PhantomData,
+            _marker,
         }
     }
 
@@ -1009,9 +1081,13 @@ fn append_allow_header(allow_header: &mut AllowHeader, method: &'static str) {
     }
 }
 
-impl<B, E> Clone for MethodRouter<B, E> {
+impl<S, B, E, R> Clone for MethodRouter<S, B, E, R>
+where
+    S: Clone,
+{
     fn clone(&self) -> Self {
         Self {
+            state: self.state.clone(),
             get: self.get.clone(),
             head: self.head.clone(),
             delete: self.delete.clone(),
@@ -1022,12 +1098,12 @@ impl<B, E> Clone for MethodRouter<B, E> {
             trace: self.trace.clone(),
             fallback: self.fallback.clone(),
             allow_header: self.allow_header.clone(),
-            _request_body: PhantomData,
+            _marker: self._marker,
         }
     }
 }
 
-impl<B, E> Default for MethodRouter<B, E>
+impl<S, B, E> Default for MethodRouter<S, B, E, MissingState>
 where
     B: Send + 'static,
 {
@@ -1036,9 +1112,10 @@ where
     }
 }
 
-impl<B, E> Service<Request<B>> for MethodRouter<B, E>
+impl<S, B, E> Service<Request<B>> for MethodRouter<S, B, E, WithState>
 where
     B: HttpBody,
+    S: Clone + Send + Sync + 'static,
 {
     type Response = Response;
     type Error = E;
@@ -1049,7 +1126,7 @@ where
         Poll::Ready(Ok(()))
     }
 
-    fn call(&mut self, req: Request<B>) -> Self::Future {
+    fn call(&mut self, mut req: Request<B>) -> Self::Future {
         macro_rules! call {
             (
                 $req:expr,
@@ -1070,6 +1147,7 @@ where
 
         // written with a pattern match like this to ensure we call all routes
         let Self {
+            state,
             get,
             head,
             delete,
@@ -1080,9 +1158,17 @@ where
             trace,
             fallback,
             allow_header,
-            _request_body: _,
+            _marker,
         } = self;
 
+        if req.extensions().get::<State<S>>().is_none() {
+            // the `unwrap` is safe because `self.state` is always some if `R = WithState`, which it is
+            let prev = req
+                .extensions_mut()
+                .insert(State(state.as_ref().unwrap().clone()));
+            debug_assert!(prev.is_none());
+        }
+
         call!(req, method, HEAD, head);
         call!(req, method, HEAD, get);
         call!(req, method, GET, get);
@@ -1120,7 +1206,7 @@ mod tests {
 
     #[tokio::test]
     async fn method_not_allowed_by_default() {
-        let mut svc = MethodRouter::new();
+        let mut svc = MethodRouter::new().state(());
         let (status, _, body) = call(Method::GET, &mut svc).await;
         assert_eq!(status, StatusCode::METHOD_NOT_ALLOWED);
         assert!(body.is_empty());
@@ -1128,7 +1214,7 @@ mod tests {
 
     #[tokio::test]
     async fn get_handler() {
-        let mut svc = MethodRouter::new().get(ok);
+        let mut svc = MethodRouter::without_state().get(ok);
         let (status, _, body) = call(Method::GET, &mut svc).await;
         assert_eq!(status, StatusCode::OK);
         assert_eq!(body, "ok");
@@ -1136,7 +1222,7 @@ mod tests {
 
     #[tokio::test]
     async fn get_accepts_head() {
-        let mut svc = MethodRouter::new().get(ok);
+        let mut svc = MethodRouter::without_state().get(ok);
         let (status, _, body) = call(Method::HEAD, &mut svc).await;
         assert_eq!(status, StatusCode::OK);
         assert!(body.is_empty());
@@ -1144,7 +1230,7 @@ mod tests {
 
     #[tokio::test]
     async fn head_takes_precedence_over_get() {
-        let mut svc = MethodRouter::new().head(created).get(ok);
+        let mut svc = MethodRouter::without_state().head(created).get(ok);
         let (status, _, body) = call(Method::HEAD, &mut svc).await;
         assert_eq!(status, StatusCode::CREATED);
         assert!(body.is_empty());
@@ -1152,7 +1238,7 @@ mod tests {
 
     #[tokio::test]
     async fn merge() {
-        let mut svc = get(ok).merge(post(ok));
+        let mut svc = get(ok).merge(post(ok)).state(());
 
         let (status, _, _) = call(Method::GET, &mut svc).await;
         assert_eq!(status, StatusCode::OK);
@@ -1163,7 +1249,7 @@ mod tests {
 
     #[tokio::test]
     async fn layer() {
-        let mut svc = MethodRouter::new()
+        let mut svc = MethodRouter::without_state()
             .get(|| async { std::future::pending::<()>().await })
             .layer(RequireAuthorizationLayer::bearer("password"));
 
@@ -1178,7 +1264,7 @@ mod tests {
 
     #[tokio::test]
     async fn route_layer() {
-        let mut svc = MethodRouter::new()
+        let mut svc = MethodRouter::without_state()
             .get(|| async { std::future::pending::<()>().await })
             .route_layer(RequireAuthorizationLayer::bearer("password"));
 
@@ -1204,7 +1290,7 @@ mod tests {
                         delete_service(ServeDir::new("."))
                             .handle_error(|_| async { StatusCode::NOT_FOUND }),
                     )
-                    .fallback((|| async { StatusCode::NOT_FOUND }).into_service())
+                    .fallback(|| async { StatusCode::NOT_FOUND })
                     .put(ok)
                     .layer(
                         ServiceBuilder::new()
@@ -1221,7 +1307,7 @@ mod tests {
 
     #[tokio::test]
     async fn sets_allow_header() {
-        let mut svc = MethodRouter::new().put(ok).patch(ok);
+        let mut svc = MethodRouter::without_state().put(ok).patch(ok);
         let (status, headers, _) = call(Method::GET, &mut svc).await;
         assert_eq!(status, StatusCode::METHOD_NOT_ALLOWED);
         assert_eq!(headers[ALLOW], "PUT,PATCH");
@@ -1229,7 +1315,7 @@ mod tests {
 
     #[tokio::test]
     async fn sets_allow_header_get_head() {
-        let mut svc = MethodRouter::new().get(ok).head(ok);
+        let mut svc = MethodRouter::without_state().get(ok).head(ok);
         let (status, headers, _) = call(Method::PUT, &mut svc).await;
         assert_eq!(status, StatusCode::METHOD_NOT_ALLOWED);
         assert_eq!(headers[ALLOW], "GET,HEAD");
@@ -1237,7 +1323,7 @@ mod tests {
 
     #[tokio::test]
     async fn empty_allow_header_by_default() {
-        let mut svc = MethodRouter::new();
+        let mut svc = MethodRouter::without_state();
         let (status, headers, _) = call(Method::PATCH, &mut svc).await;
         assert_eq!(status, StatusCode::METHOD_NOT_ALLOWED);
         assert_eq!(headers[ALLOW], "");
@@ -1247,7 +1333,7 @@ mod tests {
     async fn allow_header_when_merging() {
         let a = put(ok).patch(ok);
         let b = get(ok).head(ok);
-        let mut svc = a.merge(b);
+        let mut svc = a.merge(b).state(());
 
         let (status, headers, _) = call(Method::DELETE, &mut svc).await;
         assert_eq!(status, StatusCode::METHOD_NOT_ALLOWED);
@@ -1256,7 +1342,7 @@ mod tests {
 
     #[tokio::test]
     async fn allow_header_any() {
-        let mut svc = any(ok);
+        let mut svc = any(ok).state(());
 
         let (status, headers, _) = call(Method::GET, &mut svc).await;
         assert_eq!(status, StatusCode::OK);
@@ -1265,9 +1351,9 @@ mod tests {
 
     #[tokio::test]
     async fn allow_header_with_fallback() {
-        let mut svc = MethodRouter::new().get(ok).fallback(
+        let mut svc = MethodRouter::without_state()
-            (|| async { (StatusCode::METHOD_NOT_ALLOWED, "Method not allowed") }).into_service(),
+            .get(ok)
-        );
+            .fallback(|| async { (StatusCode::METHOD_NOT_ALLOWED, "Method not allowed") });
 
         let (status, headers, _) = call(Method::DELETE, &mut svc).await;
         assert_eq!(status, StatusCode::METHOD_NOT_ALLOWED);
@@ -1289,9 +1375,7 @@ mod tests {
             }
         }
 
-        let mut svc = MethodRouter::new()
+        let mut svc = MethodRouter::without_state().get(ok).fallback(fallback);
-            .get(ok)
-            .fallback(fallback.into_service());
 
         let (status, _, _) = call(Method::GET, &mut svc).await;
         assert_eq!(status, StatusCode::OK);
@@ -1309,7 +1393,7 @@ mod tests {
         expected = "Overlapping method route. Cannot add two method routes that both handle `GET`"
     )]
     async fn handler_overlaps() {
-        let _: MethodRouter = get(ok).get(ok);
+        let _: MethodRouter<(), Body, Infallible, _> = get(ok).get(ok);
     }
 
     #[tokio::test]
@@ -1317,17 +1401,18 @@ mod tests {
         expected = "Overlapping method route. Cannot add two method routes that both handle `POST`"
     )]
     async fn service_overlaps() {
-        let _: MethodRouter = post_service(ok.into_service()).post_service(ok.into_service());
+        let _: MethodRouter<(), Body, Infallible, _> =
+            post_service(ok.into_service(())).post_service(ok.into_service(()));
     }
 
     #[tokio::test]
     async fn get_head_does_not_overlap() {
-        let _: MethodRouter = get(ok).head(ok);
+        let _: MethodRouter<(), Body, Infallible, _> = get(ok).head(ok);
     }
 
     #[tokio::test]
     async fn head_get_does_not_overlap() {
-        let _: MethodRouter = head(ok).get(ok);
+        let _: MethodRouter<(), Body, Infallible, _> = head(ok).get(ok);
     }
 
     async fn call<S>(method: Method, svc: &mut S) -> (StatusCode, HeaderMap, String)

axum/src/routing/mod.rs

@@ -4,6 +4,7 @@ use self::{future::RouteFuture, not_found::NotFound};
 use crate::{
     body::{boxed, Body, Bytes, HttpBody},
     extract::connect_info::IntoMakeServiceWithConnectInfo,
+    handler::{Handler, IntoExtensionService},
     response::Response,
     routing::strip_prefix::StripPrefix,
     util::try_downcast,
@@ -68,7 +69,7 @@ pub struct Router<S, B = Body, R = MissingState> {
     // If `R == WithState` then state is `Some`
     // `R` cannot have other values
     state: Option<S>,
-    routes: HashMap<RouteId, Endpoint<B>>,
+    routes: HashMap<RouteId, Endpoint<S, B, R>>,
     node: Arc<Node>,
     fallback: Fallback<B>,
     _marker: PhantomData<R>,
@@ -141,10 +142,27 @@ where
     }
 
     /// TODO(david): docs
-    pub fn state(self, state: S) -> Router<S, B, WithState> {
+    pub fn state(self, state: S) -> Router<S, B, WithState>
+    where
+        S: Clone,
+    {
+        let routes = self
+            .routes
+            .into_iter()
+            .map(|(id, endpoint)| {
+                let endpoint = match endpoint {
+                    Endpoint::MethodRouter(router) => {
+                        Endpoint::MethodRouter(router.state(state.clone()))
+                    }
+                    Endpoint::Route(route) => Endpoint::Route(route),
+                };
+                (id, endpoint)
+            })
+            .collect();
+
         Router {
             state: Some(state),
-            routes: self.routes,
+            routes,
             node: self.node,
             fallback: self.fallback,
             _marker: PhantomData,
@@ -155,6 +173,7 @@ where
 impl<S, B> Router<S, B, WithState>
 where
     B: HttpBody + Send + 'static,
+    S: Clone,
 {
     /// TODO(david): docs
     pub fn with_state(state: S) -> Self {
@@ -162,6 +181,16 @@ where
     }
 }
 
+impl<B> Router<(), B, WithState>
+where
+    B: HttpBody + Send + 'static,
+{
+    /// TODO(david): docs
+    pub fn without_state() -> Self {
+        Router::with_state(())
+    }
+}
+
 impl<S, B, R> Router<S, B, R>
 where
     B: HttpBody + Send + 'static,
@@ -169,72 +198,78 @@ where
     R: 'static,
 {
     #[doc = include_str!("../docs/routing/route.md")]
-    pub fn route<T>(mut self, path: &str, service: T) -> Self
+    pub fn route(
+        mut self,
+        path: &str,
+        // TODO(david): constrain this so it only accepts methods
+        // routers containing handlers
+        method_router: MethodRouter<S, B, Infallible, MissingState>,
+    ) -> Self {
+        self
+    }
+
+    /// TODO(david): docs
+    pub fn route_service<T>(mut self, path: &str, service: T) -> Self
     where
         T: Service<Request<B>, Response = Response, Error = Infallible> + Clone + Send + 'static,
         T::Future: Send + 'static,
     {
-        if path.is_empty() {
-            panic!("Paths must start with a `/`. Use \"/\" for root routes");
-        } else if !path.starts_with('/') {
-            panic!("Paths must start with a `/`");
-        }
-
-        // Downcase to `WithState` rather than `R` because `Router<S, B, R>` only implements
-        // `Service` if `R == WithState` so any other type of `R` cannot be passed to `.router` in
-        // the first place
-        let service = match try_downcast::<Router<S, B, WithState>, _>(service) {
-            Ok(_) => {
-                panic!("Invalid route: `Router::route` cannot be used with `Router`s. Use `Router::nest` instead")
-            }
-            Err(svc) => svc,
-        };
-
-        let id = RouteId::next();
-
-        let service = match try_downcast::<MethodRouter<B, Infallible>, _>(service) {
-            Ok(method_router) => {
-                if let Some((route_id, Endpoint::MethodRouter(prev_method_router))) = self
-                    .node
-                    .path_to_route_id
-                    .get(path)
-                    .and_then(|route_id| self.routes.get(route_id).map(|svc| (*route_id, svc)))
-                {
-                    // if we're adding a new `MethodRouter` to a route that already has one just
-                    // merge them. This makes `.route("/", get(_)).route("/", post(_))` work
-                    let service =
-                        Endpoint::MethodRouter(prev_method_router.clone().merge(method_router));
-                    self.routes.insert(route_id, service);
-                    return self;
-                } else {
-                    Endpoint::MethodRouter(method_router)
-                }
-            }
-            Err(service) => Endpoint::Route(Route::new(service)),
-        };
-
-        let mut node =
-            Arc::try_unwrap(Arc::clone(&self.node)).unwrap_or_else(|node| (*node).clone());
-        if let Err(err) = node.insert(path, id) {
-            panic!("Invalid route: {}", err);
-        }
-        self.node = Arc::new(node);
-
-        self.routes.insert(id, service);
-
         self
+
+        // if path.is_empty() {
+        //     panic!("Paths must start with a `/`. Use \"/\" for root routes");
+        // } else if !path.starts_with('/') {
+        //     panic!("Paths must start with a `/`");
+        // }
+
+        // // Downcase to `WithState` rather than `R` because `Router<S, B, R>` only implements
+        // // `Service` if `R == WithState` so any other type of `R` cannot be passed to `.router` in
+        // // the first place
+        // let service = match try_downcast::<Router<S, B, WithState>, _>(service) {
+        //     Ok(_) => {
+        //         panic!("Invalid route: `Router::route` cannot be used with `Router`s. Use `Router::nest` instead")
+        //     }
+        //     Err(svc) => svc,
+        // };
+
+        // let id = RouteId::next();
+
+        // let service = match try_downcast::<MethodRouter<B, Infallible>, _>(service) {
+        //     Ok(method_router) => {
+        //         if let Some((route_id, Endpoint::MethodRouter(prev_method_router))) = self
+        //             .node
+        //             .path_to_route_id
+        //             .get(path)
+        //             .and_then(|route_id| self.routes.get(route_id).map(|svc| (*route_id, svc)))
+        //         {
+        //             // if we're adding a new `MethodRouter` to a route that already has one just
+        //             // merge them. This makes `.route("/", get(_)).route("/", post(_))` work
+        //             let service =
+        //                 Endpoint::MethodRouter(prev_method_router.clone().merge(method_router));
+        //             self.routes.insert(route_id, service);
+        //             return self;
+        //         } else {
+        //             Endpoint::MethodRouter(method_router)
+        //         }
+        //     }
+        //     Err(service) => Endpoint::Route(Route::new(service)),
+        // };
+
+        // let mut node =
+        //     Arc::try_unwrap(Arc::clone(&self.node)).unwrap_or_else(|node| (*node).clone());
+        // if let Err(err) = node.insert(path, id) {
+        //     panic!("Invalid route: {}", err);
+        // }
+        // self.node = Arc::new(node);
+
+        // self.routes.insert(id, service);
+
+        // self
     }
 
     #[doc = include_str!("../docs/routing/nest.md")]
     pub fn nest(mut self, mut path: &str, router: Router<S, B, MissingState>) -> Self {
-        if path.is_empty() {
+        validate_path_for_nest(&mut path);
-            // nesting at `""` and `"/"` should mean the same thing
-            path = "/";
-        }
-
-        if path.contains('*') {
-            panic!("Invalid route: nested routes cannot contain wildcards (*)");
-        }
 
         let prefix = path;
 
@@ -268,7 +303,9 @@ where
                     &full_path,
                     method_router.layer(layer_fn(|s| StripPrefix::new(s, prefix))),
                 ),
-                Endpoint::Route(route) => self.route(&full_path, StripPrefix::new(route, prefix)),
+                Endpoint::Route(route) => {
+                    self.route_service(&full_path, StripPrefix::new(route, prefix))
+                }
             };
         }
 
@@ -283,14 +320,7 @@ where
         T: Service<Request<B>, Response = Response, Error = Infallible> + Clone + Send + 'static,
         T::Future: Send + 'static,
     {
-        if path.is_empty() {
+        validate_path_for_nest(&mut path);
-            // nesting at `""` and `"/"` should mean the same thing
-            path = "/";
-        }
-
-        if path.contains('*') {
-            panic!("Invalid route: nested routes cannot contain wildcards (*)");
-        }
 
         let prefix = path;
 
@@ -301,14 +331,14 @@ where
         };
 
         let svc = strip_prefix::StripPrefix::new(svc, prefix);
-        self = self.route(&path, svc.clone());
+        self = self.route_service(&path, svc.clone());
 
         // `/*rest` is not matched by `/` so we need to also register a router at the
         // prefix itself. Otherwise if you were to nest at `/foo` then `/foo` itself
         // wouldn't match, which it should
-        self = self.route(prefix, svc.clone());
+        self = self.route_service(prefix, svc.clone());
         // same goes for `/foo/`, that should also match
-        self = self.route(&format!("{}/", prefix), svc);
+        self = self.route_service(&format!("{}/", prefix), svc);
 
         self
     }
@@ -335,7 +365,7 @@ where
                 .expect("no path for route id. This is a bug in axum. Please file an issue");
             self = match route {
                 Endpoint::MethodRouter(route) => self.route(path, route),
-                Endpoint::Route(route) => self.route(path, route),
+                Endpoint::Route(route) => self.route_service(path, route),
             };
         }
 
@@ -433,7 +463,17 @@ where
     }
 
     #[doc = include_str!("../docs/routing/fallback.md")]
-    pub fn fallback<T>(mut self, svc: T) -> Self
+    pub fn fallback<H, T>(mut self, handler: H) -> Self
+    where
+        H: Handler<S, T, B>,
+        T: 'static,
+        S: Clone + Send + Sync + 'static,
+    {
+        self.fallback_service(IntoExtensionService::new(handler))
+    }
+
+    /// TODO(david): docs
+    pub fn fallback_service<T>(mut self, svc: T) -> Self
     where
         T: Service<Request<B>, Response = Response, Error = Infallible> + Clone + Send + 'static,
         T::Future: Send + 'static,
@@ -441,7 +481,13 @@ where
         self.fallback = Fallback::Custom(Route::new(svc));
         self
     }
+}
 
+impl<S, B> Router<S, B, WithState>
+where
+    B: HttpBody + Send + 'static,
+    S: Clone + Send + Sync + 'static,
+{
     /// Convert this router into a [`MakeService`], that is a [`Service`] whose
     /// response is another service.
     ///
@@ -473,13 +519,7 @@ where
     pub fn into_make_service_with_connect_info<C>(self) -> IntoMakeServiceWithConnectInfo<Self, C> {
         IntoMakeServiceWithConnectInfo::new(self)
     }
-}
 
-impl<S, B> Router<S, B, WithState>
-where
-    B: HttpBody + Send + 'static,
-    S: Clone + Send + Sync + 'static,
-{
     #[inline]
     fn call_route(
         &self,
@@ -515,10 +555,6 @@ where
 
         url_params::insert_url_params(req.extensions_mut(), match_.params);
 
-        // the `unwrap` is safe because `self.state` is always some if `R = WithState`, which it is
-        req.extensions_mut()
-            .insert(crate::extract::State(self.state.as_ref().unwrap().clone()));
-
         let mut route = self
             .routes
             .get(&id)
@@ -560,6 +596,12 @@ where
 
         let path = req.uri().path().to_owned();
 
+        // the `unwrap` is safe because `self.state` is always some if `R = WithState`, which it is
+        let prev = req
+            .extensions_mut()
+            .insert(crate::extract::State(self.state.as_ref().unwrap().clone()));
+        debug_assert!(prev.is_none());
+
         match self.node.at(&path) {
             Ok(match_) => self.call_route(match_, req),
             Err(
@@ -580,6 +622,17 @@ pub enum MissingState {}
 #[derive(Copy, Clone, Debug)]
 pub enum WithState {}
 
+fn validate_path_for_nest(path: &mut &str) {
+    if path.is_empty() {
+        // nesting at `""` and `"/"` should mean the same thing
+        *path = "/";
+    }
+
+    if path.contains('*') {
+        panic!("Invalid route: nested routes cannot contain wildcards (*)");
+    }
+}
+
 /// Wrapper around `matchit::Router` that supports merging two `Router`s.
 #[derive(Clone, Default)]
 struct Node {
@@ -656,12 +709,15 @@ impl<B, E> Fallback<B, E> {
     }
 }
 
-enum Endpoint<B> {
+enum Endpoint<S, B, R> {
-    MethodRouter(MethodRouter<B>),
+    MethodRouter(MethodRouter<S, B, Infallible, R>),
     Route(Route<B>),
 }
 
-impl<B> Clone for Endpoint<B> {
+impl<S, B, R> Clone for Endpoint<S, B, R>
+where
+    S: Clone,
+{
     fn clone(&self) -> Self {
         match self {
             Endpoint::MethodRouter(inner) => Endpoint::MethodRouter(inner.clone()),
@@ -670,7 +726,10 @@ impl<B> Clone for Endpoint<B> {
     }
 }
 
-impl<B> fmt::Debug for Endpoint<B> {
+impl<S, B, R> fmt::Debug for Endpoint<S, B, R>
+where
+    S: fmt::Debug,
+{
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
             Self::MethodRouter(inner) => inner.fmt(f),

axum/src/routing/tests/fallback.rs

@@ -1,11 +1,10 @@
 use super::*;
-use crate::handler::Handler;
 
 #[tokio::test]
 async fn basic() {
     let app = Router::new()
         .route("/foo", get(|| async {}))
-        .fallback((|| async { "fallback" }).into_service())
+        .fallback(|| async { "fallback" })
         .state(());
 
     let client = TestClient::new(app);
@@ -21,7 +20,7 @@ async fn basic() {
 async fn nest() {
     let app = Router::new()
         .nest("/foo", Router::new().route("/bar", get(|| async {})))
-        .fallback((|| async { "fallback" }).into_service())
+        .fallback(|| async { "fallback" })
         .state(());
 
     let client = TestClient::new(app);
@@ -38,10 +37,7 @@ async fn or() {
     let one = Router::new().route("/one", get(|| async {}));
     let two = Router::new().route("/two", get(|| async {}));
 
-    let app = one
+    let app = one.merge(two).fallback(|| async { "fallback" }).state(());
-        .merge(two)
-        .fallback((|| async { "fallback" }).into_service())
-        .state(());
 
     let client = TestClient::new(app);
 

axum/src/routing/tests/mod.rs

@@ -147,7 +147,10 @@ async fn routing_between_services() {
                 }),
             ),
         )
-        .route("/two", on_service(MethodFilter::GET, handle.into_service()));
+        .route(
+            "/two",
+            on_service(MethodFilter::GET, handle.into_service(())),
+        );
 
     let client = TestClient::new(app.state(()));
 
@@ -445,7 +448,11 @@ async fn middleware_still_run_for_unmatched_requests() {
     expected = "Invalid route: `Router::route` cannot be used with `Router`s. Use `Router::nest` instead"
 )]
 async fn routing_to_router_panics() {
-    TestClient::new(Router::new().route("/", Router::new().state(())).state(()));
+    TestClient::new(
+        Router::new()
+            .route_service("/", Router::new().state(()))
+            .state(()),
+    );
 }
 
 #[tokio::test]
@@ -520,8 +527,8 @@ async fn different_methods_added_in_different_routes_deeply_nested() {
 #[should_panic(expected = "Cannot merge two `Router`s that both have a fallback")]
 async fn merging_routers_with_fallbacks_panics() {
     async fn fallback() {}
-    let one = Router::new().fallback(fallback.into_service());
+    let one = Router::new().fallback(fallback);
-    let two = Router::new().fallback(fallback.into_service());
+    let two = Router::new().fallback(fallback);
     TestClient::new(one.merge(two).state(()));
 }
 
@@ -529,7 +536,7 @@ async fn merging_routers_with_fallbacks_panics() {
 #[should_panic(expected = "Cannot nest `Router`s that has a fallback")]
 async fn nesting_router_with_fallbacks_panics() {
     async fn fallback() {}
-    let one = Router::new().fallback(fallback.into_service());
+    let one = Router::new().fallback(fallback);
     let app = Router::new().nest("/", one);
     TestClient::new(app.state(()));
 }
@@ -569,7 +576,7 @@ async fn head_content_length_through_hyper_server() {
 
 #[tokio::test]
 async fn head_content_length_through_hyper_server_that_hits_fallback() {
-    let app = Router::new().fallback((|| async { "foo" }).into_service());
+    let app = Router::new().fallback(|| async { "foo" });
 
     let client = TestClient::new(app.state(()));
 

axum/src/routing/tests/nest.rs

@@ -114,7 +114,10 @@ async fn nesting_router_at_empty_path() {
 
 #[tokio::test]
 async fn nesting_handler_at_root() {
-    let app = Router::new().nest_service("/", get(|uri: Uri| async move { uri.to_string() }));
+    let app = Router::new().nest_service(
+        "/",
+        get(|uri: Uri| async move { uri.to_string() }).state(()),
+    );
 
     let client = TestClient::new(app.state(()));
 
@@ -183,7 +186,7 @@ async fn nested_service_sees_stripped_uri() {
         "/foo",
         Router::new().nest(
             "/bar",
-            Router::new().route(
+            Router::new().route_service(
                 "/baz",
                 service_fn(|req: Request<Body>| async move {
                     let body = boxed(Body::from(req.uri().to_string()));
@@ -204,12 +207,15 @@ async fn nested_service_sees_stripped_uri() {
 async fn nest_static_file_server() {
     let app = Router::new().nest_service(
         "/static",
-        get_service(ServeDir::new(".")).handle_error(|error| async move {
+        get_service(ServeDir::new("."))
-            (
+            .handle_error(|error| async move {
-                StatusCode::INTERNAL_SERVER_ERROR,
+                (
-                format!("Unhandled internal error: {}", error),
+                    StatusCode::INTERNAL_SERVER_ERROR,
-            )
+                    format!("Unhandled internal error: {}", error),
-        }),
+                )
+            })
+            // TODO(david): having to do this on services isn't good
+            .state(()),
     );
 
     let client = TestClient::new(app.state(()));
@@ -330,7 +336,7 @@ async fn outer_middleware_still_see_whole_url() {
         .route("/foo", get(handler))
         .route("/foo/bar", get(handler))
         .nest("/one", Router::new().route("/two", get(handler)))
-        .fallback(handler.into_service())
+        .fallback(handler)
         .layer(tower::layer::layer_fn(SetUriExtension));
 
     let client = TestClient::new(app.state(()));
@@ -366,7 +372,7 @@ async fn nest_at_capture() {
 
 #[tokio::test]
 async fn nest_with_and_without_trailing() {
-    let app = Router::new().nest_service("/foo", get(|| async {}));
+    let app = Router::new().nest_service("/foo", get(|| async {}).state(()));
 
     let client = TestClient::new(app.state(()));