fix(ext/fetch): set accept-encoding: identity if range header is present (#16197)

https://fetch.spec.whatwg.org/#http-network-or-cache-fetch

> If httpRequest’s header list contains `Range`, then append
(`Accept-Encoding`, `identity`)
> to httpRequest’s header list.
> 
> This avoids a failure when handling content codings with a part of an
encoded response.
> Additionally, many servers mistakenly ignore `Range` headers if a
non-identity encoding is accepted.

2 files changed, 13 insertions, 3 deletions

diff --git a/ext/fetch/lib.rs b/ext/fetch/lib.rs
index c141c3065..5a95fbd30 100644
--- a/ext/fetch/lib.rs
+++ b/ext/fetch/lib.rs
@@ -34,7 +34,9 @@ use http::header::CONTENT_LENGTH;
 use reqwest::header::HeaderMap;
 use reqwest::header::HeaderName;
 use reqwest::header::HeaderValue;
+use reqwest::header::ACCEPT_ENCODING;
 use reqwest::header::HOST;
+use reqwest::header::RANGE;
 use reqwest::header::USER_AGENT;
 use reqwest::redirect::Policy;
 use reqwest::Body;
@@ -288,16 +290,26 @@ where
         None
       };
 
+      let mut header_map = HeaderMap::new();
       for (key, value) in headers {
         let name = HeaderName::from_bytes(&key)
           .map_err(|err| type_error(err.to_string()))?;
         let v = HeaderValue::from_bytes(&value)
           .map_err(|err| type_error(err.to_string()))?;
+
         if !matches!(name, HOST | CONTENT_LENGTH) {
-          request = request.header(name, v);
+          header_map.append(name, v);
         }
       }
 
+      if header_map.contains_key(RANGE) {
+        // https://fetch.spec.whatwg.org/#http-network-or-cache-fetch step 18
+        // If httpRequest’s header list contains `Range`, then append (`Accept-Encoding`, `identity`)
+        header_map
+          .insert(ACCEPT_ENCODING, HeaderValue::from_static("identity"));
+      }
+      request = request.headers(header_map);
+
       let options = state.borrow::<Options>();
       if let Some(request_builder_hook) = options.request_builder_hook {
         request = request_builder_hook(request);
diff --git a/tools/wpt/expectation.json b/tools/wpt/expectation.json
index d713775d0..a3dcaa70c 100644
--- a/tools/wpt/expectation.json
+++ b/tools/wpt/expectation.json
@@ -3266,12 +3266,10 @@
     "range": {
       "general.any.html": [
         "Privileged header not allowed for guard type: request-no-cors",
-        "Fetch with range header will be sent with Accept-Encoding: identity",
         "Cross Origin Fetch with non safe range header"
       ],
       "general.any.worker.html": [
         "Privileged header not allowed for guard type: request-no-cors",
-        "Fetch with range header will be sent with Accept-Encoding: identity",
         "Cross Origin Fetch with non safe range header"
       ],
       "general.window.html": false