implemented default handlers for error middleware and associated unit tests

actix-web/src/middleware/err_handlers.rs

@@ -30,6 +30,8 @@ pub enum ErrorHandlerResponse<B> {
 
 type ErrorHandler<B> = dyn Fn(ServiceResponse<B>) -> Result<ErrorHandlerResponse<B>>;
 
+type DefaultHandler<B> = Option<Rc<ErrorHandler<B>>>;
+
 /// Middleware for registering custom status code based error handlers.
 ///
 /// Register handlers with the `ErrorHandlers::handler()` method to register a custom error handler
@@ -54,6 +56,8 @@ type ErrorHandler<B> = dyn Fn(ServiceResponse<B>) -> Result<ErrorHandlerResponse
 ///     .service(web::resource("/").route(web::get().to(HttpResponse::InternalServerError)));
 /// ```
 pub struct ErrorHandlers<B> {
+    default_client: DefaultHandler<B>,
+    default_server: DefaultHandler<B>,
     handlers: Handlers<B>,
 }
 
@@ -62,6 +66,8 @@ type Handlers<B> = Rc<AHashMap<StatusCode, Box<ErrorHandler<B>>>>;
 impl<B> Default for ErrorHandlers<B> {
     fn default() -> Self {
         ErrorHandlers {
+            default_client: Default::default(),
+            default_server: Default::default(),
             handlers: Default::default(),
         }
     }
@@ -83,6 +89,46 @@ impl<B> ErrorHandlers<B> {
             .insert(status, Box::new(handler));
         self
     }
+
+    pub fn default_handler<F>(self, handler: F) -> Self
+    where
+        F: Fn(ServiceResponse<B>) -> Result<ErrorHandlerResponse<B>> + 'static,
+    {
+        let handler = Rc::new(handler);
+        Self {
+            default_server: Some(handler.clone()),
+            default_client: Some(handler),
+            ..self
+        }
+    }
+
+    pub fn default_handler_server<F>(self, handler: F) -> Self
+    where
+        F: Fn(ServiceResponse<B>) -> Result<ErrorHandlerResponse<B>> + 'static,
+    {
+        Self { default_server: Some(Rc::new(handler)), ..self }
+    }
+
+    pub fn default_handler_client<F>(self, handler: F) -> Self
+    where
+        F: Fn(ServiceResponse<B>) -> Result<ErrorHandlerResponse<B>> + 'static,
+    {
+        Self { default_client: Some(Rc::new(handler)), ..self }
+    }
+
+    fn get_handler<'a>(
+        status: &StatusCode,
+        default_client: Option<&'a dyn Fn(ServiceResponse<B>) -> Result<ErrorHandlerResponse<B>>>,
+        default_server: Option<&'a dyn Fn(ServiceResponse<B>) -> Result<ErrorHandlerResponse<B>>>,
+        handlers: &'a Handlers<B>,
+    ) -> Option<&'a dyn Fn(ServiceResponse<B>) -> Result<ErrorHandlerResponse<B>>>
+    {
+        handlers
+            .get(status)
+            .map(|h| h.as_ref())
+            .or_else(|| status.is_client_error().then(|| default_client).flatten())
+            .or_else(|| status.is_server_error().then(|| default_server).flatten())
+    }
 }
 
 impl<S, B> Transform<S, ServiceRequest> for ErrorHandlers<B>
@@ -99,13 +145,22 @@ where
 
     fn new_transform(&self, service: S) -> Self::Future {
         let handlers = self.handlers.clone();
-        Box::pin(async move { Ok(ErrorHandlersMiddleware { service, handlers }) })
+        let default_client = self.default_client.clone();
+        let default_server = self.default_server.clone();
+        Box::pin(async move { Ok(ErrorHandlersMiddleware {
+            service,
+            default_client,
+            default_server,
+            handlers
+        }) })
     }
 }
 
 #[doc(hidden)]
 pub struct ErrorHandlersMiddleware<S, B> {
     service: S,
+    default_client: DefaultHandler<B>,
+    default_server: DefaultHandler<B>,
     handlers: Handlers<B>,
 }
 
@@ -123,8 +178,10 @@ where
 
     fn call(&self, req: ServiceRequest) -> Self::Future {
         let handlers = self.handlers.clone();
+        let default_client = self.default_client.clone();
+        let default_server = self.default_server.clone();
         let fut = self.service.call(req);
-        ErrorHandlersFuture::ServiceFuture { fut, handlers }
+        ErrorHandlersFuture::ServiceFuture { fut, default_client, default_server, handlers }
     }
 }
 
@@ -137,6 +194,8 @@ pin_project! {
         ServiceFuture {
             #[pin]
             fut: Fut,
+            default_client: DefaultHandler<B>,
+            default_server: DefaultHandler<B>,
             handlers: Handlers<B>,
         },
         ErrorHandlerFuture {
@@ -153,10 +212,17 @@ where
 
     fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
         match self.as_mut().project() {
-            ErrorHandlersProj::ServiceFuture { fut, handlers } => {
+            ErrorHandlersProj::ServiceFuture { fut, default_client, default_server, handlers } => {
                 let res = ready!(fut.poll(cx))?;
+                let status = res.status();
 
-                match handlers.get(&res.status()) {
+                let handler = ErrorHandlers::get_handler(
+                    &status,
+                    default_client.as_mut().map(|f| Rc::as_ref(f)),
+                    default_server.as_mut().map(|f| Rc::as_ref(f)),
+                    handlers
+                );
+                match handler {
                     Some(handler) => match handler(res)? {
                         ErrorHandlerResponse::Response(res) => Poll::Ready(Ok(res)),
                         ErrorHandlerResponse::Future(fut) => {
@@ -165,8 +231,7 @@ where
 
                             self.poll(cx)
                         }
-                    },
-
+                    }
                     None => Poll::Ready(Ok(res.map_into_left_body())),
                 }
             }
@@ -298,4 +363,103 @@ mod tests {
             "error in error handler"
         );
     }
+
+    #[actix_rt::test]
+    async fn default_error_handler() {
+        #[allow(clippy::unnecessary_wraps)]
+        fn error_handler<B>(mut res: ServiceResponse<B>) -> Result<ErrorHandlerResponse<B>> {
+            res.response_mut()
+                .headers_mut()
+                .insert(CONTENT_TYPE, HeaderValue::from_static("0001"));
+            Ok(ErrorHandlerResponse::Response(res.map_into_left_body()))
+        }
+
+        let make_mw = |status| async move {
+            ErrorHandlers::new()
+                .default_handler(error_handler)
+                .new_transform(test::status_service(status).into_service())
+                .await
+                .unwrap()
+        };
+        let mw_server = make_mw(StatusCode::INTERNAL_SERVER_ERROR).await;
+        let mw_client = make_mw(StatusCode::BAD_REQUEST).await;
+
+        let resp = test::call_service(&mw_client, TestRequest::default().to_srv_request()).await;
+        assert_eq!(resp.headers().get(CONTENT_TYPE).unwrap(), "0001");
+
+        let resp = test::call_service(&mw_server, TestRequest::default().to_srv_request()).await;
+        assert_eq!(resp.headers().get(CONTENT_TYPE).unwrap(), "0001");
+    }
+
+    #[actix_rt::test]
+    async fn default_handlers_separate_client_server() {
+        #[allow(clippy::unnecessary_wraps)]
+        fn error_handler_client<B>(mut res: ServiceResponse<B>) -> Result<ErrorHandlerResponse<B>> {
+            res.response_mut()
+                .headers_mut()
+                .insert(CONTENT_TYPE, HeaderValue::from_static("0001"));
+            Ok(ErrorHandlerResponse::Response(res.map_into_left_body()))
+        }
+
+        #[allow(clippy::unnecessary_wraps)]
+        fn error_handler_server<B>(mut res: ServiceResponse<B>) -> Result<ErrorHandlerResponse<B>> {
+            res.response_mut()
+                .headers_mut()
+                .insert(CONTENT_TYPE, HeaderValue::from_static("0002"));
+            Ok(ErrorHandlerResponse::Response(res.map_into_left_body()))
+        }
+
+        let make_mw = |status| async move {
+            ErrorHandlers::new()
+                .default_handler_server(error_handler_server)
+                .default_handler_client(error_handler_client)
+                .new_transform(test::status_service(status).into_service())
+                .await
+                .unwrap()
+        };
+        let mw_server = make_mw(StatusCode::INTERNAL_SERVER_ERROR).await;
+        let mw_client = make_mw(StatusCode::BAD_REQUEST).await;
+
+        let resp = test::call_service(&mw_client, TestRequest::default().to_srv_request()).await;
+        assert_eq!(resp.headers().get(CONTENT_TYPE).unwrap(), "0001");
+
+        let resp = test::call_service(&mw_server, TestRequest::default().to_srv_request()).await;
+        assert_eq!(resp.headers().get(CONTENT_TYPE).unwrap(), "0002");
+    }
+
+    #[actix_rt::test]
+    async fn default_handlers_specialization() {
+        #[allow(clippy::unnecessary_wraps)]
+        fn error_handler_client<B>(mut res: ServiceResponse<B>) -> Result<ErrorHandlerResponse<B>> {
+            res.response_mut()
+                .headers_mut()
+                .insert(CONTENT_TYPE, HeaderValue::from_static("0001"));
+            Ok(ErrorHandlerResponse::Response(res.map_into_left_body()))
+        }
+
+        #[allow(clippy::unnecessary_wraps)]
+        fn error_handler_specific<B>(mut res: ServiceResponse<B>) -> Result<ErrorHandlerResponse<B>> {
+            res.response_mut()
+                .headers_mut()
+                .insert(CONTENT_TYPE, HeaderValue::from_static("0003"));
+            Ok(ErrorHandlerResponse::Response(res.map_into_left_body()))
+        }
+
+        let make_mw = |status| async move {
+            ErrorHandlers::new()
+                .default_handler_client(error_handler_client)
+                .handler(StatusCode::UNPROCESSABLE_ENTITY, error_handler_specific)
+                .new_transform(test::status_service(status).into_service())
+                .await
+                .unwrap()
+        };
+        let mw_client = make_mw(StatusCode::BAD_REQUEST).await;
+        let mw_specific = make_mw(StatusCode::UNPROCESSABLE_ENTITY).await;
+
+        let resp = test::call_service(&mw_client, TestRequest::default().to_srv_request()).await;
+        assert_eq!(resp.headers().get(CONTENT_TYPE).unwrap(), "0001");
+
+        let resp = test::call_service(&mw_specific, TestRequest::default().to_srv_request()).await;
+        assert_eq!(resp.headers().get(CONTENT_TYPE).unwrap(), "0003");
+    }
 }