Add web::ReqData<T> extractor (#1748)

Co-authored-by: Jonas Platte <jonas@lumeo.com>

CHANGES.md

@@ -1,11 +1,17 @@
 # Changes
 
 ## Unreleased - 2020-xx-xx
-* Implement Logger middleware regex exclude pattern [#1723]
-* Print unconfigured `Data<T>` type when attempting extraction. [#1743]
+### Added
+* Implement `exclude_regex` for Logger middleware. [#1723]
+* Add request-local data extractor `web::ReqData`. [#1748]
+
+### Changed
+* Print non-configured `Data<T>` type when attempting extraction. [#1743]
 
 [#1723]: https://github.com/actix/actix-web/pull/1723
 [#1743]: https://github.com/actix/actix-web/pull/1743
+[#1748]: https://github.com/actix/actix-web/pull/1748
+
 
 ## 3.1.0 - 2020-09-29
 ### Changed

src/data.rs

@@ -20,25 +20,20 @@ pub(crate) type FnDataFactory =
 
 /// Application data.
 ///
-/// Application data is an arbitrary data attached to the app.
-/// Application data is available to all routes and could be added
-/// during application configuration process
-/// with `App::data()` method.
+/// Application level data is a piece of arbitrary data attached to the app, scope, or resource.
+/// Application data is available to all routes and can be added during the application
+/// configuration process via `App::data()`.
 ///
-/// Application data could be accessed by using `Data<T>`
-/// extractor where `T` is data type.
+/// Application data can be accessed by using `Data<T>` extractor where `T` is data type.
 ///
-/// **Note**: http server accepts an application factory rather than
-/// an application instance. Http server constructs an application
-/// instance for each thread, thus application data must be constructed
-/// multiple times. If you want to share data between different
-/// threads, a shareable object should be used, e.g. `Send + Sync`. Application
-/// data does not need to be `Send` or `Sync`. Internally `Data` type
-/// uses `Arc`. if your data implements `Send` + `Sync` traits you can
-/// use `web::Data::new()` and avoid double `Arc`.
+/// **Note**: http server accepts an application factory rather than an application instance. HTTP
+/// server constructs an application instance for each thread, thus application data must be
+/// constructed multiple times. If you want to share data between different threads, a shareable
+/// object should be used, e.g. `Send + Sync`. Application data does not need to be `Send`
+/// or `Sync`. Internally `Data` uses `Arc`.
 ///
-/// If route data is not set for a handler, using `Data<T>` extractor would
-/// cause *Internal Server Error* response.
+/// If route data is not set for a handler, using `Data<T>` extractor would cause *Internal
+/// Server Error* response.
 ///
 /// ```rust
 /// use std::sync::Mutex;
@@ -48,7 +43,7 @@ pub(crate) type FnDataFactory =
 ///     counter: usize,
 /// }
 ///
-/// /// Use `Data<T>` extractor to access data in handler.
+/// /// Use the `Data<T>` extractor to access data in a handler.
 /// async fn index(data: web::Data<Mutex<MyData>>) -> impl Responder {
 ///     let mut data = data.lock().unwrap();
 ///     data.counter += 1;
@@ -71,10 +66,6 @@ pub struct Data<T: ?Sized>(Arc<T>);
 
 impl<T> Data<T> {
     /// Create new `Data` instance.
-    ///
-    /// Internally `Data` type uses `Arc`. if your data implements
-    /// `Send` + `Sync` traits you can use `web::Data::new()` and
-    /// avoid double `Arc`.
     pub fn new(state: T) -> Data<T> {
         Data(Arc::new(state))
     }

src/lib.rs

@@ -81,6 +81,7 @@ mod handler;
 mod info;
 pub mod middleware;
 mod request;
+mod request_data;
 mod resource;
 mod responder;
 mod rmap;

src/request_data.rs

@@ -0,0 +1,175 @@
+use std::{any::type_name, ops::Deref};
+
+use actix_http::error::{Error, ErrorInternalServerError};
+use futures_util::future;
+
+use crate::{dev::Payload, FromRequest, HttpRequest};
+
+/// Request-local data extractor.
+///
+/// Request-local data is arbitrary data attached to an individual request, usually
+/// by middleware. It can be set via `extensions_mut` on [`HttpRequest`][htr_ext_mut]
+/// or [`ServiceRequest`][srv_ext_mut].
+///
+/// Unlike app data, request data is dropped when the request has finished processing. This makes it
+/// useful as a kind of messaging system between middleware and request handlers. It uses the same
+/// types-as-keys storage system as app data.
+///
+/// # Mutating Request Data
+/// Note that since extractors must output owned data, only types that `impl Clone` can use this
+/// extractor. A clone is taken of the required request data and can, therefore, not be directly
+/// mutated in-place. To mutate request data, continue to use [`HttpRequest::extensions_mut`] or
+/// re-insert the cloned data back into the extensions map. A `DerefMut` impl is intentionally not
+/// provided to make this potential foot-gun more obvious.
+///
+/// # Example
+/// ```rust,no_run
+/// # use actix_web::{web, HttpResponse, HttpRequest, Responder};
+///
+/// #[derive(Debug, Clone, PartialEq)]
+/// struct FlagFromMiddleware(String);
+///
+/// /// Use the `ReqData<T>` extractor to access request data in a handler.
+/// async fn handler(
+///     req: HttpRequest,
+///     opt_flag: Option<web::ReqData<FlagFromMiddleware>>,
+/// ) -> impl Responder {
+///     // use an optional extractor if the middleware is
+///     // not guaranteed to add this type of requests data
+///     if let Some(flag) = opt_flag {
+///         assert_eq!(&flag.into_inner(), req.extensions().get::<FlagFromMiddleware>().unwrap());
+///     }
+///     
+///     HttpResponse::Ok()
+/// }
+/// ```
+///
+/// [htr_ext_mut]: crate::HttpRequest::extensions_mut
+/// [srv_ext_mut]: crate::dev::ServiceRequest::extensions_mut
+#[derive(Debug, Clone)]
+pub struct ReqData<T: Clone + 'static>(T);
+
+impl<T: Clone + 'static> ReqData<T> {
+    /// Consumes the `ReqData`, returning it's wrapped data.
+    pub fn into_inner(self) -> T {
+        self.0
+    }
+}
+
+impl<T: Clone + 'static> Deref for ReqData<T> {
+    type Target = T;
+
+    fn deref(&self) -> &T {
+        &self.0
+    }
+}
+
+impl<T: Clone + 'static> FromRequest for ReqData<T> {
+    type Config = ();
+    type Error = Error;
+    type Future = future::Ready<Result<Self, Error>>;
+
+    fn from_request(req: &HttpRequest, _: &mut Payload) -> Self::Future {
+        if let Some(st) = req.extensions().get::<T>() {
+            future::ok(ReqData(st.clone()))
+        } else {
+            log::debug!(
+                "Failed to construct App-level ReqData extractor. \
+                 Request path: {:?} (type: {})",
+                req.path(),
+                type_name::<T>(),
+            );
+            future::err(ErrorInternalServerError(
+                "Missing expected request extension data",
+            ))
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use std::{cell::RefCell, rc::Rc};
+
+    use futures_util::TryFutureExt as _;
+
+    use super::*;
+    use crate::{
+        dev::Service,
+        http::{Method, StatusCode},
+        test::{init_service, TestRequest},
+        web, App, HttpMessage, HttpResponse,
+    };
+
+    #[actix_rt::test]
+    async fn req_data_extractor() {
+        let mut srv = init_service(
+            App::new()
+                .wrap_fn(|req, srv| {
+                    if req.method() == Method::POST {
+                        req.extensions_mut().insert(42u32);
+                    }
+
+                    srv.call(req)
+                })
+                .service(web::resource("/test").to(
+                    |req: HttpRequest, data: Option<ReqData<u32>>| {
+                        if req.method() != Method::POST {
+                            assert!(data.is_none());
+                        }
+
+                        if let Some(data) = data {
+                            assert_eq!(*data, 42);
+                            assert_eq!(
+                                Some(data.into_inner()),
+                                req.extensions().get::<u32>().copied()
+                            );
+                        }
+
+                        HttpResponse::Ok()
+                    },
+                )),
+        )
+        .await;
+
+        let req = TestRequest::get().uri("/test").to_request();
+        let resp = srv.call(req).await.unwrap();
+        assert_eq!(resp.status(), StatusCode::OK);
+
+        let req = TestRequest::post().uri("/test").to_request();
+        let resp = srv.call(req).await.unwrap();
+        assert_eq!(resp.status(), StatusCode::OK);
+    }
+
+    #[actix_rt::test]
+    async fn req_data_internal_mutability() {
+        let mut srv = init_service(
+            App::new()
+                .wrap_fn(|req, srv| {
+                    let data_before = Rc::new(RefCell::new(42u32));
+                    req.extensions_mut().insert(data_before);
+
+                    srv.call(req).map_ok(|res| {
+                        {
+                            let ext = res.request().extensions();
+                            let data_after = ext.get::<Rc<RefCell<u32>>>().unwrap();
+                            assert_eq!(*data_after.borrow(), 53u32);
+                        }
+
+                        res
+                    })
+                })
+                .default_service(web::to(|data: ReqData<Rc<RefCell<u32>>>| {
+                    assert_eq!(*data.borrow(), 42);
+                    *data.borrow_mut() += 11;
+                    assert_eq!(*data.borrow(), 53);
+
+                    HttpResponse::Ok()
+                })),
+        )
+        .await;
+
+        let req = TestRequest::get().uri("/test").to_request();
+        let resp = srv.call(req).await.unwrap();
+        assert_eq!(resp.status(), StatusCode::OK);
+    }
+}

src/web.rs

@@ -19,6 +19,7 @@ use crate::service::WebService;
 pub use crate::config::ServiceConfig;
 pub use crate::data::Data;
 pub use crate::request::HttpRequest;
+pub use crate::request_data::ReqData;
 pub use crate::types::*;
 
 /// Create resource for a specific path.