Add `ServiceConfig::configure`

CHANGES.md

@@ -1,11 +1,13 @@
 # Changes
 
 ## Unreleased - 2021-xx-xx
+### Added
+* Added `ServiceConfig::configure` to allow easy nesting of configuration. [#1988]
 ### Changed
 * Feature `cookies` is now optional and enabled by default. [#1981]
 
 [#1981]: https://github.com/actix/actix-web/pull/1981
-
+[#1988]: https://github.com/actix/actix-web/pull/1988
 
 ## 4.0.0-beta.3 - 2021-02-10
 * Update `actix-web-codegen` to `0.5.0-beta.1`.

src/config.rs

@@ -199,6 +199,17 @@ impl ServiceConfig {
         self
     }
 
+    /// Run external configuration as part of the application building process
+    ///
+    /// Counterpart to [`App::configure()`](crate::App::configure) that allows for easy nesting.
+    pub fn configure<F>(&mut self, f: F) -> &mut Self
+    where
+        F: FnOnce(&mut ServiceConfig),
+    {
+        f(self);
+        self
+    }
+
     /// Configure route for a specific path.
     ///
     /// Counterpart to [`App::route()`](crate::App::route).