tweak default_service docs

src/app.rs

@@ -238,8 +238,12 @@ where
 
     /// Default service that is invoked when no matching resource could be found.
     ///
-    /// You must use a [`Route`] as default service:
+    /// You can use a [`Route`] as default service.
     ///
+    /// If a default service is not registered, an empty `404 Not Found` response will be sent to
+    /// the client instead.
+    ///
+    /// # Examples
     /// ```
     /// use actix_web::{web, App, HttpResponse};
     ///
@@ -248,10 +252,8 @@ where
     /// }
     ///
     /// let app = App::new()
-    ///     .service(
-    ///         web::resource("/index.html").route(web::get().to(index)))
-    ///     .default_service(
-    ///         web::route().to(|| HttpResponse::NotFound()));
+    ///     .service(web::resource("/index.html").route(web::get().to(index)))
+    ///     .default_service(web::to(|| HttpResponse::NotFound()));
     /// ```
     pub fn default_service<F, U>(mut self, svc: F) -> Self
     where

src/app_service.rs

@@ -72,7 +72,7 @@ where
             })))
         });
 
-        // App config
+        // create App config to pass to child services
         let mut config = AppService::new(config, default.clone());
 
         // register services

src/resource.rs

@@ -313,10 +313,12 @@ where
     }
 
     /// Default service to be used if no matching route could be found.
-    /// You can pass a [`Route`] as default_service.
     ///
-    /// If no default service is specified, a `405 Method Not Allowed` response will be returned to the caller.  
-    /// [`Resource`] does **not** inherit the default handler specified on the parent [`App`](crate::App) or [`Scope`](crate::Scope).
+    /// You can use a [`Route`] as default service.
+    ///
+    /// If a default service is not registered, an empty `405 Method Not Allowed` response will be
+    /// sent to the client instead. Unlike [`Scope`](crate::Scope)s, a [`Resource`] does **not**
+    /// inherit its parent's default service.
     pub fn default_service<F, U>(mut self, f: F) -> Self
     where
         F: IntoServiceFactory<U, ServiceRequest>,

src/scope.rs

@@ -262,10 +262,10 @@ where
         )
     }
 
-    /// Default service to be used if no matching route could be found.
+    /// Default service to be used if no matching resource could be found.
     ///
     /// If a default service is not registered, it will fall back to the default service of
-    /// the parent [`App`](crate::App) (see [`App::default_service`](crate::App::default_service).
+    /// the parent [`App`](crate::App) (see [`App::default_service`](crate::App::default_service)).
     pub fn default_service<F, U>(mut self, f: F) -> Self
     where
         F: IntoServiceFactory<U, ServiceRequest>,