add Allow header to resource's default 405 handler

actix-web/src/guard/mod.rs

@@ -286,11 +286,26 @@ pub fn Method(method: HttpMethod) -> impl Guard {
     MethodGuard(method)
 }
 
+#[derive(Debug, Clone)]
+pub(crate) struct RegisteredMethods(pub(crate) Vec<HttpMethod>);
+
 /// HTTP method guard.
-struct MethodGuard(HttpMethod);
+#[derive(Debug)]
+pub(crate) struct MethodGuard(HttpMethod);
 
 impl Guard for MethodGuard {
     fn check(&self, ctx: &GuardContext<'_>) -> bool {
+        let registered = ctx.req_data_mut().remove::<RegisteredMethods>();
+
+        if let Some(mut methods) = registered {
+            eprintln!("here one");
+            methods.0.push(self.0.clone());
+            ctx.req_data_mut().insert(methods);
+        } else {
+            ctx.req_data_mut()
+                .insert(RegisteredMethods(vec![self.0.clone()]));
+        }
+
         ctx.head().method == self.0
     }
 }

actix-web/src/resource.rs

@@ -13,8 +13,9 @@ use crate::{
     body::MessageBody,
     data::Data,
     dev::{ensure_leading_slash, AppService, ResourceDef},
-    guard::Guard,
+    guard::{self, Guard},
     handler::Handler,
+    http::header,
     route::{Route, RouteService},
     service::{
         BoxedHttpService, BoxedHttpServiceFactory, HttpServiceFactory, ServiceRequest,
@@ -66,7 +67,19 @@ impl Resource {
             guards: Vec::new(),
             app_data: None,
             default: boxed::factory(fn_service(|req: ServiceRequest| async {
+                use crate::HttpMessage as _;
+
+                let allowed = req.extensions().get::<guard::RegisteredMethods>().cloned();
+
+                if let Some(methods) = allowed {
+                    Ok(req.into_response(
+                        HttpResponse::MethodNotAllowed()
+                            .insert_header(header::Allow(methods.0))
+                            .finish(),
+                    ))
+                } else {
                     Ok(req.into_response(HttpResponse::MethodNotAllowed()))
+                }
             })),
         }
     }
@@ -606,7 +619,11 @@ mod tests {
     async fn test_default_resource() {
         let srv = init_service(
             App::new()
-                .service(web::resource("/test").route(web::get().to(HttpResponse::Ok)))
+                .service(
+                    web::resource("/test")
+                        .route(web::get().to(HttpResponse::Ok))
+                        .route(web::delete().to(HttpResponse::Ok)),
+                )
                 .default_service(|r: ServiceRequest| {
                     ok(r.into_response(HttpResponse::BadRequest()))
                 }),
@@ -621,6 +638,10 @@ mod tests {
             .to_request();
         let resp = call_service(&srv, req).await;
         assert_eq!(resp.status(), StatusCode::METHOD_NOT_ALLOWED);
+        assert_eq!(
+            resp.headers().get(header::ALLOW).unwrap().as_bytes(),
+            b"GET, DELETE"
+        );
 
         let srv = init_service(
             App::new().service(