Implement register_data method on Resource and Scope. (#1094)

* Implement `register_data` method on `Resource` and `Scope`.

* Split Scope::register_data tests out from Scope::data tests.

* CHANGES.md: Mention {Scope,Resource}::register_data.

src/scope.rs

@@ -148,11 +148,20 @@ where
     ///     );
     /// }
     /// ```
-    pub fn data<U: 'static>(mut self, data: U) -> Self {
+    pub fn data<U: 'static>(self, data: U) -> Self {
+        self.register_data(Data::new(data))
+    }
+
+    /// Set or override application data.
+    ///
+    /// This method has the same effect as [`Scope::data`](#method.data), except
+    /// that instead of taking a value of some type `T`, it expects a value of
+    /// type `Data<T>`. Use a `Data<T>` extractor to retrieve its value.
+    pub fn register_data<U: 'static>(mut self, data: Data<U>) -> Self {
         if self.data.is_none() {
             self.data = Some(Extensions::new());
         }
-        self.data.as_mut().unwrap().insert(Data::new(data));
+        self.data.as_mut().unwrap().insert(data);
         self
     }
 
@@ -1082,6 +1091,24 @@ mod tests {
         assert_eq!(resp.status(), StatusCode::OK);
     }
 
+    #[test]
+    fn test_override_register_data() {
+        let mut srv = init_service(App::new().register_data(web::Data::new(1usize)).service(
+            web::scope("app").register_data(web::Data::new(10usize)).route(
+                "/t",
+                web::get().to(|data: web::Data<usize>| {
+                    assert_eq!(*data, 10);
+                    let _ = data.clone();
+                    HttpResponse::Ok()
+                }),
+            ),
+        ));
+
+        let req = TestRequest::with_uri("/app/t").to_request();
+        let resp = call_service(&mut srv, req);
+        assert_eq!(resp.status(), StatusCode::OK);
+    }
+
     #[test]
     fn test_scope_config() {
         let mut srv =