add double compress layer test

Cargo.toml

@@ -109,6 +109,7 @@ actix-test = { version = "0.1.0-beta.10", features = ["openssl", "rustls"] }
 awc = { version = "3.0.0-beta.17", features = ["openssl"] }
 
 brotli2 = "0.3.2"
+const-str = "0.3"
 criterion = { version = "0.3", features = ["html_reports"] }
 env_logger = "0.9"
 flate2 = "1.0.13"

actix-http/src/encoding/encoder.rs

@@ -56,16 +56,16 @@ impl<B: MessageBody> Encoder<B> {
     }
 
     pub fn response(encoding: ContentEncoding, head: &mut ResponseHead, body: B) -> Self {
-        let should_encode = !(head.headers().contains_key(&CONTENT_ENCODING)
-            || head.status == StatusCode::SWITCHING_PROTOCOLS
-            || head.status == StatusCode::NO_CONTENT
-            || encoding == ContentEncoding::Identity);
-
         // no need to compress an empty body
         if matches!(body.size(), BodySize::None) {
             return Self::none();
         }
 
+        let should_encode = !(head.headers().contains_key(&CONTENT_ENCODING)
+            || head.status == StatusCode::SWITCHING_PROTOCOLS
+            || head.status == StatusCode::NO_CONTENT
+            || encoding == ContentEncoding::Identity);
+
         let body = match body.try_into_bytes() {
             Ok(body) => EncoderBody::Full { body },
             Err(body) => EncoderBody::Stream { body },
@@ -301,7 +301,7 @@ impl ContentEncoder {
                 Some(ContentEncoder::Zstd(encoder))
             }
 
-            ContentEncoding::Identity => None,
+            _ => None,
         }
     }
 

src/middleware/compress.rs

@@ -217,3 +217,63 @@ static SUPPORTED_ENCODINGS: Lazy<Vec<Encoding>> = Lazy::new(|| {
 
     encodings
 });
+
+// move cfg(feature) to prevents_double_compressing if more tests are added
+#[cfg(feature = "compress-gzip")]
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::{middleware::DefaultHeaders, test, web, App};
+
+    pub fn gzip_decode(bytes: impl AsRef<[u8]>) -> Vec<u8> {
+        use std::io::Read as _;
+        let mut decoder = flate2::read::GzDecoder::new(bytes.as_ref());
+        let mut buf = Vec::new();
+        decoder.read_to_end(&mut buf).unwrap();
+        buf
+    }
+
+    #[actix_rt::test]
+    async fn prevents_double_compressing() {
+        const D: &str = "hello world ";
+        const DATA: &str = const_str::repeat!(D, 100);
+
+        let app = test::init_service({
+            App::new()
+                .wrap(Compress::default())
+                .route(
+                    "/single",
+                    web::get().to(move || HttpResponse::Ok().body(DATA)),
+                )
+                .service(
+                    web::resource("/double")
+                        .wrap(Compress::default())
+                        .wrap(DefaultHeaders::new().add(("x-double", "true")))
+                        .route(web::get().to(move || HttpResponse::Ok().body(DATA))),
+                )
+        })
+        .await;
+
+        let req = test::TestRequest::default()
+            .uri("/single")
+            .insert_header((header::ACCEPT_ENCODING, "gzip"))
+            .to_request();
+        let res = test::call_service(&app, req).await;
+        assert_eq!(res.status(), StatusCode::OK);
+        assert_eq!(res.headers().get("x-double"), None);
+        assert_eq!(res.headers().get(header::CONTENT_ENCODING).unwrap(), "gzip");
+        let bytes = test::read_body(res).await;
+        assert_eq!(gzip_decode(bytes), DATA.as_bytes());
+
+        let req = test::TestRequest::default()
+            .uri("/double")
+            .insert_header((header::ACCEPT_ENCODING, "gzip"))
+            .to_request();
+        let res = test::call_service(&app, req).await;
+        assert_eq!(res.status(), StatusCode::OK);
+        assert_eq!(res.headers().get("x-double").unwrap(), "true");
+        assert_eq!(res.headers().get(header::CONTENT_ENCODING).unwrap(), "gzip");
+        let bytes = test::read_body(res).await;
+        assert_eq!(gzip_decode(bytes), DATA.as_bytes());
+    }
+}