rework Handler trait (#2549)

src/handler.rs

@@ -3,9 +3,8 @@ use std::future::Future;
 use actix_service::{boxed, fn_service};
 
 use crate::{
-    body::MessageBody,
     service::{BoxedHttpServiceFactory, ServiceRequest, ServiceResponse},
-    BoxError, FromRequest, HttpResponse, Responder,
+    FromRequest, HttpResponse, Responder,
 };
 
 /// The interface for request handlers.
@@ -18,7 +17,7 @@ use crate::{
 ///   [`HttpResponse`] (i.e., it implements the [`Responder`] trait).
 ///
 /// # Compiler Errors
-/// If you get the error `the trait Handler<_, _, _> is not implemented`, then your handler does not
+/// If you get the error `the trait Handler<_> is not implemented`, then your handler does not
 /// fulfill one or more of the above requirements.
 ///
 /// Unfortunately we cannot provide a better compile error message (while keeping the trait's
@@ -78,22 +77,18 @@ use crate::{
 /// [arity]: https://en.wikipedia.org/wiki/Arity
 /// [`from_request`]: FromRequest::from_request
 /// [on_unimpl]: https://github.com/rust-lang/rust/issues/29628
-pub trait Handler<Args, R>: Clone + 'static
-where
-    R: Future,
-    R::Output: Responder,
-{
-    fn call(&self, args: Args) -> R;
+pub trait Handler<Args>: Clone + 'static {
+    type Output;
+    type Future: Future<Output = Self::Output>;
+
+    fn call(&self, args: Args) -> Self::Future;
 }
 
-pub(crate) fn handler_service<F, Args, R>(handler: F) -> BoxedHttpServiceFactory
+pub(crate) fn handler_service<F, Args>(handler: F) -> BoxedHttpServiceFactory
 where
-    F: Handler<Args, R>,
+    F: Handler<Args>,
     Args: FromRequest,
-    R: Future,
-    R::Output: Responder,
-    <R::Output as Responder>::Body: MessageBody,
-    <<R::Output as Responder>::Body as MessageBody>::Error: Into<BoxError>,
+    F::Output: Responder,
 {
     boxed::factory(fn_service(move |req: ServiceRequest| {
         let handler = handler.clone();
@@ -125,14 +120,16 @@ where
 /// factory_tuple! { A B C }  // implements Handler for types: fn(A, B, C) -> R
 /// ```
 macro_rules! factory_tuple ({ $($param:ident)* } => {
-    impl<Func, $($param,)* R> Handler<($($param,)*), R> for Func
-    where Func: Fn($($param),*) -> R + Clone + 'static,
-          R: Future,
-          R::Output: Responder,
+    impl<Func, Fut, $($param,)*> Handler<($($param,)*)> for Func
+    where Func: Fn($($param),*) -> Fut + Clone + 'static,
+          Fut: Future,
     {
+        type Output = Fut::Output;
+        type Future = Fut;
+
         #[inline]
         #[allow(non_snake_case)]
-        fn call(&self, ($($param,)*): ($($param,)*)) -> R {
+        fn call(&self, ($($param,)*): ($($param,)*)) -> Self::Future {
             (self)($($param,)*)
         }
     }

src/resource.rs

@@ -20,7 +20,7 @@ use crate::{
         BoxedHttpService, BoxedHttpServiceFactory, HttpServiceFactory, ServiceRequest,
         ServiceResponse,
     },
-    BoxError, Error, FromRequest, HttpResponse, Responder,
+    Error, FromRequest, HttpResponse, Responder,
 };
 
 /// A collection of [`Route`]s that respond to the same path pattern.
@@ -230,14 +230,11 @@ where
     /// # fn index(req: HttpRequest) -> HttpResponse { unimplemented!() }
     /// App::new().service(web::resource("/").route(web::route().to(index)));
     /// ```
-    pub fn to<F, Args, R>(mut self, handler: F) -> Self
+    pub fn to<F, Args>(mut self, handler: F) -> Self
     where
-        F: Handler<Args, R>,
+        F: Handler<Args>,
         Args: FromRequest + 'static,
-        R: Future + 'static,
-        R::Output: Responder + 'static,
-        <R::Output as Responder>::Body: MessageBody,
-        <<R::Output as Responder>::Body as MessageBody>::Error: Into<BoxError>,
+        F::Output: Responder + 'static,
     {
         self.routes.push(Route::new().to(handler));
         self

src/route.rs

@@ -1,4 +1,4 @@
-use std::{future::Future, mem, rc::Rc};
+use std::{mem, rc::Rc};
 
 use actix_http::Method;
 use actix_service::{
@@ -8,11 +8,10 @@ use actix_service::{
 use futures_core::future::LocalBoxFuture;
 
 use crate::{
-    body::MessageBody,
     guard::{self, Guard},
     handler::{handler_service, Handler},
     service::{BoxedHttpServiceFactory, ServiceRequest, ServiceResponse},
-    BoxError, Error, FromRequest, HttpResponse, Responder,
+    Error, FromRequest, HttpResponse, Responder,
 };
 
 /// A request handler with [guards](guard).
@@ -176,14 +175,11 @@ impl Route {
     ///     );
     /// }
     /// ```
-    pub fn to<F, Args, R>(mut self, handler: F) -> Self
+    pub fn to<F, Args>(mut self, handler: F) -> Self
     where
-        F: Handler<Args, R>,
+        F: Handler<Args>,
         Args: FromRequest + 'static,
-        R: Future + 'static,
-        R::Output: Responder + 'static,
-        <R::Output as Responder>::Body: MessageBody,
-        <<R::Output as Responder>::Body as MessageBody>::Error: Into<BoxError>,
+        F::Output: Responder + 'static,
     {
         self.service = handler_service(handler);
         self

src/web.rs

@@ -1,14 +1,14 @@
 //! Essentials helper functions and types for application registration.
 
-use std::{error::Error as StdError, future::Future};
+use std::future::Future;
 
 use actix_http::Method;
 use actix_router::IntoPatterns;
 pub use bytes::{Buf, BufMut, Bytes, BytesMut};
 
 use crate::{
-    body::MessageBody, error::BlockingError, extract::FromRequest, handler::Handler,
-    resource::Resource, route::Route, scope::Scope, service::WebService, Responder,
+    error::BlockingError, extract::FromRequest, handler::Handler, resource::Resource,
+    route::Route, scope::Scope, service::WebService, Responder,
 };
 
 pub use crate::config::ServiceConfig;
@@ -146,14 +146,11 @@ pub fn method(method: Method) -> Route {
 ///         web::to(index))
 /// );
 /// ```
-pub fn to<F, Args, R>(handler: F) -> Route
+pub fn to<F, Args>(handler: F) -> Route
 where
-    F: Handler<Args, R>,
+    F: Handler<Args>,
     Args: FromRequest + 'static,
-    R: Future + 'static,
-    R::Output: Responder + 'static,
-    <R::Output as Responder>::Body: MessageBody + 'static,
-    <<R::Output as Responder>::Body as MessageBody>::Error: Into<Box<dyn StdError + 'static>>,
+    F::Output: Responder + 'static,
 {
     Route::new().to(handler)
 }