major cleanup of middleware module (#1875)

* major cleanup of middleware module

* update changelog

src/middleware/compress.rs

@@ -1,45 +1,47 @@
-//! `Middleware` for compressing response body.
-use std::cmp;
-use std::future::Future;
-use std::marker::PhantomData;
-use std::pin::Pin;
-use std::str::FromStr;
-use std::task::{Context, Poll};
+//! For middleware documentation, see [`Compress`].
 
-use actix_http::body::MessageBody;
-use actix_http::encoding::Encoder;
-use actix_http::http::header::{ContentEncoding, ACCEPT_ENCODING};
-use actix_http::Error;
+use std::{
+    cmp,
+    future::Future,
+    marker::PhantomData,
+    pin::Pin,
+    str::FromStr,
+    task::{Context, Poll},
+};
+
+use actix_http::{
+    body::MessageBody,
+    encoding::Encoder,
+    http::header::{ContentEncoding, ACCEPT_ENCODING},
+    Error,
+};
 use actix_service::{Service, Transform};
 use futures_util::future::{ok, Ready};
 use pin_project::pin_project;
 
-use crate::dev::BodyEncoding;
-use crate::service::{ServiceRequest, ServiceResponse};
+use crate::{
+    dev::BodyEncoding,
+    service::{ServiceRequest, ServiceResponse},
+};
 
-#[derive(Debug, Clone)]
-/// `Middleware` for compressing response body.
+/// Middleware for compressing response payloads.
 ///
-/// Use `BodyEncoding` trait for overriding response compression.
-/// To disable compression set encoding to `ContentEncoding::Identity` value.
+/// Use `BodyEncoding` trait for overriding response compression. To disable compression set
+/// encoding to `ContentEncoding::Identity`.
 ///
+/// # Usage
 /// ```rust
 /// use actix_web::{web, middleware, App, HttpResponse};
 ///
-/// fn main() {
-///     let app = App::new()
-///         .wrap(middleware::Compress::default())
-///         .service(
-///             web::resource("/test")
-///                 .route(web::get().to(|| HttpResponse::Ok()))
-///                 .route(web::head().to(|| HttpResponse::MethodNotAllowed()))
-///         );
-/// }
+/// let app = App::new()
+///     .wrap(middleware::Compress::default())
+///     .default_service(web::to(|| HttpResponse::NotFound()));
 /// ```
+#[derive(Debug, Clone)]
 pub struct Compress(ContentEncoding);
 
 impl Compress {
-    /// Create new `Compress` middleware with default encoding.
+    /// Create new `Compress` middleware with the specified encoding.
     pub fn new(encoding: ContentEncoding) -> Self {
         Compress(encoding)
     }
@@ -84,9 +86,7 @@ where
     type Error = Error;
     type Future = CompressResponse<S, B>;
 
-    fn poll_ready(&mut self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
-        self.service.poll_ready(cx)
-    }
+    actix_service::forward_ready!(service);
 
     #[allow(clippy::borrow_interior_mutable_const)]
     fn call(&mut self, req: ServiceRequest) -> Self::Future {
@@ -109,7 +109,6 @@ where
     }
 }
 
-#[doc(hidden)]
 #[pin_project]
 pub struct CompressResponse<S, B>
 where