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::{forward_ready, Service, ServiceRequest, ServiceResponse, Transform},
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
66pub struct CatchPanicMiddleware<S> {
67    service: Rc<S>,
68}
69
70impl<S, B> Service<ServiceRequest> for CatchPanicMiddleware<S>
71where
72    S: Service<ServiceRequest, Response = ServiceResponse<B>, Error = actix_web::Error> + 'static,
73{
74    type Response = ServiceResponse<B>;
75    type Error = actix_web::Error;
76    type Future = LocalBoxFuture<'static, Result<Self::Response, Self::Error>>;
77
78    forward_ready!(service);
79
80    fn call(&self, req: ServiceRequest) -> Self::Future {
81        AssertUnwindSafe(self.service.call(req))
82            .catch_unwind()
83            .map(move |res| match res {
84                Ok(Ok(res)) => Ok(res),
85                Ok(Err(svc_err)) => Err(svc_err),
86                Err(_panic_err) => Err(error::ErrorInternalServerError("")),
87            })
88            .boxed_local()
89    }
90}
91
92#[cfg(test)]
93mod tests {
94    use actix_web::{
95        body::{to_bytes, MessageBody},
96        dev::{Service as _, ServiceFactory},
97        http::StatusCode,
98        test, web, App, Error,
99    };
100
101    use super::*;
102
103    fn test_app() -> App<
104        impl ServiceFactory<
105            ServiceRequest,
106            Response = ServiceResponse<impl MessageBody>,
107            Config = (),
108            InitError = (),
109            Error = Error,
110        >,
111    > {
112        App::new()
113            .wrap(CatchPanic::default())
114            .route("/", web::get().to(|| async { "content" }))
115            .route(
116                "/disco",
117                #[allow(unreachable_code)]
118                web::get().to(|| async {
119                    panic!("the disco");
120                    ""
121                }),
122            )
123    }
124
125    #[actix_web::test]
126    async fn pass_through_no_panic() {
127        let app = test::init_service(test_app()).await;
128
129        let req = test::TestRequest::default().to_request();
130        let res = test::call_service(&app, req).await;
131        assert_eq!(res.status(), StatusCode::OK);
132        let body = test::read_body(res).await;
133        assert_eq!(body, "content");
134    }
135
136    #[actix_web::test]
137    async fn catch_panic_return_internal_server_error_response() {
138        let app = test::init_service(test_app()).await;
139
140        let req = test::TestRequest::with_uri("/disco").to_request();
141        let err = match app.call(req).await {
142            Ok(_) => panic!("unexpected Ok response"),
143            Err(err) => err,
144        };
145        let res = err.error_response();
146        assert_eq!(res.status(), StatusCode::INTERNAL_SERVER_ERROR);
147        let body = to_bytes(res.into_body()).await.unwrap();
148        assert!(body.is_empty());
149    }
150}
actix_web_lab/catch_panic.rs

actix_web_lab/
catch_panic.rs
