fix(emulate): correct Firefox 147+ Accept-Language q-value

crates/wreq-util/src/emulate/macros.rs

@@ -151,32 +151,27 @@ macro_rules! header_firefox_sec_fetch {
 
 macro_rules! header_firefox_accept {
     ($headers:expr) => {
-        $headers.insert(
-            ACCEPT,
-            HeaderValue::from_static(
-                "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8",
-            ),
-        );
-        $headers.insert(ACCEPT_LANGUAGE, HeaderValue::from_static("en-US,en;q=0.5"));
-        #[cfg(feature = "emulation-compression")]
-        $headers.insert(
-            ACCEPT_ENCODING,
-            HeaderValue::from_static("gzip, deflate, br"),
-        );
+        header_firefox_accept!(@build $headers, "en-US,en;q=0.5", "gzip, deflate, br");
     };
     (zstd, $headers:expr) => {
+        header_firefox_accept!(@build $headers, "en-US,en;q=0.5", "gzip, deflate, br, zstd");
+    };
+    // Firefox 147 changed the generated q-value from dividing 1.0 across the list to
+    // decrementing by 0.1 per entry, so a two-entry list became q=0.9 (Bugzilla 2000765,
+    // landed in 0e050ae5116d).
+    (zstd_q09, $headers:expr) => {
+        header_firefox_accept!(@build $headers, "en-US,en;q=0.9", "gzip, deflate, br, zstd");
+    };
+    (@build $headers:expr, $accept_language:expr, $accept_encoding:expr) => {
         $headers.insert(
             ACCEPT,
             HeaderValue::from_static(
                 "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8",
             ),
         );
-        $headers.insert(ACCEPT_LANGUAGE, HeaderValue::from_static("en-US,en;q=0.5"));
+        $headers.insert(ACCEPT_LANGUAGE, HeaderValue::from_static($accept_language));
         #[cfg(feature = "emulation-compression")]
-        $headers.insert(
-            ACCEPT_ENCODING,
-            HeaderValue::from_static("gzip, deflate, br, zstd"),
-        );
+        $headers.insert(ACCEPT_ENCODING, HeaderValue::from_static($accept_encoding));
     };
 }
 

crates/wreq-util/src/emulate/profile/firefox.rs

@@ -380,7 +380,7 @@ mod_generator!(
 mod_generator!(
     ff147,
     ff135::build_emulation,
-    header_initializer_with_zstd,
+    header_initializer_with_zstd_q09,
     [
         (
             Windows,
@@ -408,7 +408,7 @@ mod_generator!(
 mod_generator!(
     ff148,
     ff135::build_emulation,
-    header_initializer_with_zstd,
+    header_initializer_with_zstd_q09,
     [
         (
             Windows,
@@ -436,7 +436,7 @@ mod_generator!(
 mod_generator!(
     ff149,
     ff135::build_emulation,
-    header_initializer_with_zstd,
+    header_initializer_with_zstd_q09,
     [
         (
             Windows,
@@ -465,7 +465,7 @@ mod_generator!(
     ff150,
     tls_options!(4, CIPHER_LIST_3, CURVES_2, KEY_SHARES_2),
     http2_options!(1),
-    header_initializer_with_zstd,
+    header_initializer_with_zstd_q09,
     [
         (
             Windows,
@@ -493,7 +493,7 @@ mod_generator!(
 mod_generator!(
     ff151,
     ff150::build_emulation,
-    header_initializer_with_zstd,
+    header_initializer_with_zstd_q09,
     [
         (
             Windows,
@@ -521,7 +521,7 @@ mod_generator!(
 mod_generator!(
     ff152,
     ff150::build_emulation,
-    header_initializer_with_zstd,
+    header_initializer_with_zstd_q09,
     [
         (
             Windows,

crates/wreq-util/src/emulate/profile/firefox/header.rs

@@ -35,3 +35,25 @@ pub fn header_initializer_with_zstd(ua: &'static str) -> HeaderMap {
     );
     headers
 }
+
+/// Firefox 147 and later. Identical to [`header_initializer_with_zstd`] apart from the
+/// `Accept-Language` q-value, which Firefox changed in 147 (Bugzilla 2000765).
+pub fn header_initializer_with_zstd_q09(ua: &'static str) -> HeaderMap {
+    let mut headers = HeaderMap::new();
+    header_firefox_ua!(headers, ua);
+    header_firefox_accept!(zstd_q09, headers);
+    headers.insert(
+        HeaderName::from_static("upgrade-insecure-requests"),
+        HeaderValue::from_static("1"),
+    );
+    header_firefox_sec_fetch!(headers);
+    headers.insert(
+        HeaderName::from_static("priority"),
+        HeaderValue::from_static("u=0, i"),
+    );
+    headers.insert(
+        HeaderName::from_static("te"),
+        HeaderValue::from_static("trailers"),
+    );
+    headers
+}

crates/wreq-util/tests/emulate_firefox.rs

@@ -111,3 +111,61 @@ test_emulation!(
     ["t13d1617h2_86a278354501_3cbfd9057e0d"],
     "6ea73faa8fc5aac76bded7bd238f6433"
 );
+
+/// Firefox 147 changed the generated `Accept-Language` q-value: the list used to divide 1.0
+/// across its entries, giving `q=0.5` for two, and now decrements by 0.1 per entry, giving
+/// `q=0.9`. See Bugzilla 2000765, landed in mozilla-firefox 0e050ae5116d.
+///
+/// Every profile is listed rather than a range, so adding one is a deliberate choice about
+/// which side of 147 it falls on.
+#[test]
+fn firefox_accept_language_matches_the_profile_version() {
+    use wreq::IntoEmulation;
+    use wreq_util::{Platform, Profile};
+
+    const PRE_147: &[(&str, Profile)] = &[
+        ("Firefox109", Emulation::Firefox109),
+        ("Firefox117", Emulation::Firefox117),
+        ("Firefox128", Emulation::Firefox128),
+        ("Firefox133", Emulation::Firefox133),
+        ("Firefox135", Emulation::Firefox135),
+        ("FirefoxPrivate135", Emulation::FirefoxPrivate135),
+        ("FirefoxAndroid135", Emulation::FirefoxAndroid135),
+        ("Firefox136", Emulation::Firefox136),
+        ("FirefoxPrivate136", Emulation::FirefoxPrivate136),
+        ("Firefox139", Emulation::Firefox139),
+        ("Firefox142", Emulation::Firefox142),
+        ("Firefox143", Emulation::Firefox143),
+        ("Firefox144", Emulation::Firefox144),
+        ("Firefox145", Emulation::Firefox145),
+        ("Firefox146", Emulation::Firefox146),
+    ];
+    const POST_147: &[(&str, Profile)] = &[
+        ("Firefox147", Emulation::Firefox147),
+        ("Firefox148", Emulation::Firefox148),
+        ("Firefox149", Emulation::Firefox149),
+        ("Firefox150", Emulation::Firefox150),
+        ("Firefox151", Emulation::Firefox151),
+        ("Firefox152", Emulation::Firefox152),
+    ];
+
+    fn accept_language(profile: Profile) -> String {
+        Emulation::builder()
+            .profile(profile)
+            .platform(Platform::Linux)
+            .build()
+            .into_emulation()
+            .headers
+            .get("accept-language")
+            .and_then(|value| value.to_str().ok())
+            .unwrap_or_default()
+            .to_owned()
+    }
+
+    for (name, profile) in PRE_147 {
+        assert_eq!("en-US,en;q=0.5", accept_language(*profile), "{name}");
+    }
+    for (name, profile) in POST_147 {
+        assert_eq!("en-US,en;q=0.9", accept_language(*profile), "{name}");
+    }
+}