Do compress grpc-web responses (#408)

bouk · jlizen · web-flow · commit 3962dbab7b74 · 2026-05-06T16:48:20.000-07:00
* Do compress grpc-web responses

* fix: use Infallible instead of unresolved Error type in test

---------

Co-authored-by: Jess Izen &lt;44884346+jlizen@users.noreply.github.com&gt;
diff --git a/tower-http/src/compression/mod.rs b/tower-http/src/compression/mod.rs
@@ -388,6 +388,31 @@ mod tests {
         assert_eq!(res.headers()[CONTENT_ENCODING], "gzip");
     }
 
+    #[tokio::test]
+    async fn does_compress_grpc_web() {
+        async fn handle(_req: Request<Body>) -> Result<Response<Body>, Infallible> {
+            let mut res = Response::new(Body::from(
+                "a".repeat((SizeAbove::DEFAULT_MIN_SIZE * 2) as usize),
+            ));
+            res.headers_mut()
+                .insert(CONTENT_TYPE, "application/grpc-web+proto".parse().unwrap());
+            Ok(res)
+        }
+
+        let svc = Compression::new(service_fn(handle));
+
+        let res = svc
+            .oneshot(
+                Request::builder()
+                    .header(ACCEPT_ENCODING, "gzip")
+                    .body(Body::empty())
+                    .unwrap(),
+            )
+            .await
+            .unwrap();
+        assert_eq!(res.headers()[CONTENT_ENCODING], "gzip");
+    }
+
     #[tokio::test]
     async fn compress_with_quality() {
         const DATA: &str = "Check compression quality level! Check compression quality level! Check compression quality level!";
diff --git a/tower-http/src/compression/predicate.rs b/tower-http/src/compression/predicate.rs
@@ -196,7 +196,10 @@ pub struct NotForContentType {
 
 impl NotForContentType {
     /// Predicate that wont compress gRPC responses.
-    pub const GRPC: Self = Self::const_new("application/grpc");
+    pub const GRPC: Self = Self {
+        content_type: Str::Static("application/grpc"),
+        exception: Some(Str::Static("application/grpc-web")),
+    };
 
     /// Predicate that wont compress images.
     pub const IMAGES: Self = Self {
@@ -229,13 +232,14 @@ impl Predicate for NotForContentType {
     where
         B: Body,
     {
+        let cty = content_type(response);
         if let Some(except) = &self.exception {
-            if content_type(response) == except.as_str() {
+            if cty.starts_with(except.as_str()) {
                 return true;
             }
         }
 
-        !content_type(response).starts_with(self.content_type.as_str())
+        !cty.starts_with(self.content_type.as_str())
     }
 }
 

Original file line number	Diff line number	Diff line change
`@@ -196,7 +196,10 @@ pub struct NotForContentType {`
`196`	`196`
`197`	`197`	`impl NotForContentType {`
`198`	`198`	`/// Predicate that wont compress gRPC responses.`
`199`		`- pub const GRPC: Self = Self::const_new("application/grpc");`
	`199`	`+ pub const GRPC: Self = Self {`
	`200`	`+ content_type: Str::Static("application/grpc"),`
	`201`	`+ exception: Some(Str::Static("application/grpc-web")),`
	`202`	`+ };`
`200`	`203`
`201`	`204`	`/// Predicate that wont compress images.`
`202`	`205`	`pub const IMAGES: Self = Self {`
`@@ -229,13 +232,14 @@ impl Predicate for NotForContentType {`
`229`	`232`	`where`
`230`	`233`	`B: Body,`
`231`	`234`	`{`
	`235`	`+ let cty = content_type(response);`
`232`	`236`	`if let Some(except) = &self.exception {`
`233`		`- if content_type(response) == except.as_str() {`
	`237`	`+ if cty.starts_with(except.as_str()) {`
`234`	`238`	`return true;`
`235`	`239`	`}`
`236`	`240`	`}`
`237`	`241`
`238`		`- !content_type(response).starts_with(self.content_type.as_str())`
	`242`	`+ !cty.starts_with(self.content_type.as_str())`
`239`	`243`	`}`
`240`	`244`	`}`
`241`	`245`