[rust] Reuse driver mirror URL (when available) to discover Firefox versions (#13941)

rust/src/firefox.rs

@@ -223,9 +223,11 @@ impl SeleniumManager for FirefoxManager {
             _ => {
                 self.assert_online_or_err(OFFLINE_REQUEST_ERR_MSG)?;
 
+                let driver_version_url =
+                    self.get_driver_mirror_versions_url_or_default(DRIVER_VERSIONS_URL);
                 let driver_version = match parse_json_from_url::<GeckodriverReleases>(
                     self.get_http_client(),
-                    DRIVER_VERSIONS_URL,
+                    &driver_version_url,
                 ) {
                     Ok(driver_releases) => {
                         let major_browser_version_int =

rust/src/lib.rs

@@ -1288,6 +1288,26 @@ pub trait SeleniumManager {
         }
     }
 
+    fn get_driver_mirror_versions_url_or_default<'a>(&'a self, default_url: &'a str) -> String {
+        let driver_mirror_url = self.get_driver_mirror_url();
+        if !driver_mirror_url.is_empty() {
+            let driver_versions_path = default_url.rfind('/').map(|i| &default_url[i + 1..]);
+            if let Some(path) = driver_versions_path {
+                let driver_mirror_versions_url = if driver_mirror_url.ends_with('/') {
+                    format!("{}{}", driver_mirror_url, path)
+                } else {
+                    format!("{}/{}", driver_mirror_url, path)
+                };
+                self.get_logger().debug(format!(
+                    "Using mirror URL to discover driver versions: {}",
+                    driver_mirror_versions_url
+                ));
+                return driver_mirror_versions_url;
+            }
+        }
+        default_url.to_string()
+    }
+
     fn get_driver_mirror_url_or_default<'a>(&'a self, default_url: &'a str) -> String {
         self.get_url_or_default(self.get_driver_mirror_url(), default_url)
     }