actix_web_lab/
catch_panic.rs

1use std::{
2    future::{Ready, ready},
3    panic::AssertUnwindSafe,
4    rc::Rc,
5};
6
7use actix_web::{
8    dev::{Service, ServiceRequest, ServiceResponse, Transform, forward_ready},
9    error,
10};
11use futures_core::future::LocalBoxFuture;
12use futures_util::FutureExt as _;
13
14/// A middleware to catch panics in wrapped handlers and middleware, returning empty 500 responses.
15///
16/// **This middleware should never be used as replacement for proper error handling.** See [this
17/// thread](https://github.com/actix/actix-web/issues/1501#issuecomment-627517783) for historical
18/// discussion on why Actix Web does not do this by default.
19///
20/// It is recommended that this middleware be registered last. That is, `wrap`ed after everything
21/// else except `Logger`.
22///
23/// # Examples
24///
25/// ```
26/// # use actix_web::App;
27/// use actix_web_lab::middleware::CatchPanic;
28///
29/// App::new().wrap(CatchPanic::default())
30///     # ;
31/// ```
32///
33/// ```no_run
34/// # use actix_web::App;
35/// use actix_web::middleware::{Logger, NormalizePath};
36/// use actix_web_lab::middleware::CatchPanic;
37///
38/// // recommended wrap order
39/// App::new()
40///     .wrap(NormalizePath::default())
41///     .wrap(CatchPanic::default()) // <- after everything except logger
42///     .wrap(Logger::default())
43///     # ;
44/// ```
45#[derive(Debug, Clone, Default)]
46#[non_exhaustive]
47pub struct CatchPanic;
48
49impl<S, B> Transform<S, ServiceRequest> for CatchPanic
50where
51    S: Service<ServiceRequest, Response = ServiceResponse<B>, Error = actix_web::Error> + 'static,
52{
53    type Response = ServiceResponse<B>;
54    type Error = actix_web::Error;
55    type Transform = CatchPanicMiddleware<S>;
56    type InitError = ();
57    type Future = Ready<Result<Self::Transform, Self::InitError>>;
58
59    fn new_transform(&self, service: S) -> Self::Future {
60        ready(Ok(CatchPanicMiddleware {
61            service: Rc::new(service),
62        }))
63    }
64}
65
66/// A middleware to catch panics in wrapped handlers and middleware, returning empty 500 responses.
67///
68/// See [`CatchPanic`].
69#[doc(hidden)]
70#[allow(missing_debug_implementations)]
71pub struct CatchPanicMiddleware<S> {
72    service: Rc<S>,
73}
74
75impl<S, B> Service<ServiceRequest> for CatchPanicMiddleware<S>
76where
77    S: Service<ServiceRequest, Response = ServiceResponse<B>, Error = actix_web::Error> + 'static,
78{
79    type Response = ServiceResponse<B>;
80    type Error = actix_web::Error;
81    type Future = LocalBoxFuture<'static, Result<Self::Response, Self::Error>>;
82
83    forward_ready!(service);
84
85    fn call(&self, req: ServiceRequest) -> Self::Future {
86        AssertUnwindSafe(self.service.call(req))
87            .catch_unwind()
88            .map(move |res| match res {
89                Ok(Ok(res)) => Ok(res),
90                Ok(Err(svc_err)) => Err(svc_err),
91                Err(_panic_err) => Err(error::ErrorInternalServerError("")),
92            })
93            .boxed_local()
94    }
95}
96
97#[cfg(test)]
98mod tests {
99    use actix_web::{
100        App, Error,
101        body::{MessageBody, to_bytes},
102        dev::{Service as _, ServiceFactory},
103        http::StatusCode,
104        test, web,
105    };
106
107    use super::*;
108
109    fn test_app() -> App<
110        impl ServiceFactory<
111            ServiceRequest,
112            Response = ServiceResponse<impl MessageBody>,
113            Config = (),
114            InitError = (),
115            Error = Error,
116        >,
117    > {
118        App::new()
119            .wrap(CatchPanic::default())
120            .route("/", web::get().to(|| async { "content" }))
121            .route(
122                "/disco",
123                #[allow(unreachable_code)]
124                web::get().to(|| async {
125                    panic!("the disco");
126                    ""
127                }),
128            )
129    }
130
131    #[actix_web::test]
132    async fn pass_through_no_panic() {
133        let app = test::init_service(test_app()).await;
134
135        let req = test::TestRequest::default().to_request();
136        let res = test::call_service(&app, req).await;
137        assert_eq!(res.status(), StatusCode::OK);
138        let body = test::read_body(res).await;
139        assert_eq!(body, "content");
140    }
141
142    #[actix_web::test]
143    async fn catch_panic_return_internal_server_error_response() {
144        let app = test::init_service(test_app()).await;
145
146        let req = test::TestRequest::with_uri("/disco").to_request();
147        let err = match app.call(req).await {
148            Ok(_) => panic!("unexpected Ok response"),
149            Err(err) => err,
150        };
151        let res = err.error_response();
152        assert_eq!(res.status(), StatusCode::INTERNAL_SERVER_ERROR);
153        let body = to_bytes(res.into_body()).await.unwrap();
154        assert!(body.is_empty());
155    }
156}
actix_web_lab/catch_panic.rs

actix_web_lab/
catch_panic.rs
