fix(test): only use exactly v0.24.0 geckodriver on windows

src/test/webdriver/geckodriver.rs

@@ -9,7 +9,8 @@ use target;
 
 // Keep it up to date with each `wasm-pack` release.
 // https://github.com/mozilla/geckodriver/releases/latest
-const DEFAULT_GECKODRIVER_VERSION: &str = "v0.24.0";
+const DEFAULT_GECKODRIVER_VERSION: &str = "v0.26.0";
+const DEFAULT_WINDOWS_GECKODRIVER_VERSION: &str = "v0.24.0";
 
 const GECKODRIVER_LAST_UPDATED_STAMP: &str = "geckodriver_last_updated";
 const GECKODRIVER_VERSION_STAMP: &str = "geckodriver_version";
@@ -20,8 +21,18 @@ pub fn get_or_install_geckodriver(
     cache: &Cache,
     mode: InstallMode,
 ) -> Result<PathBuf, failure::Error> {
-    if let Ok(path) = which::which("geckodriver") {
-        return Ok(path);
+    // geckodriver Windows binaries >v0.24.0 have an additional
+    // runtime dependency that we cannot be sure is present on the
+    // user's machine
+    //
+    // https://github.com/mozilla/geckodriver/issues/1617
+    // 
+    // until this is resolved, always install v0.24.0 on windows
+    if !target::WINDOWS {
+        if let Ok(path) = which::which("geckodriver") {
+            log::info!("[geckodriver] Found geckodriver at {:?}", path);
+            return Ok(path);
+        }
     }
     install_geckodriver(cache, mode.install_permitted())
 }
@@ -78,26 +89,37 @@ fn get_geckodriver_url(target: &str, ext: &str) -> String {
             .and_then(save_geckodriver_version)
     };
 
-    let geckodriver_version = match stamps::read_stamps_file_to_json() {
-        Ok(json) => {
-            if should_load_geckodriver_version_from_stamp(&json) {
-                stamps::get_stamp_value(GECKODRIVER_VERSION_STAMP, &json)
-            } else {
-                fetch_and_save_version()
+    let geckodriver_version = if target::WINDOWS {
+        log::info!(
+            "[geckodriver] Windows detected, holding geckodriver version to {}",
+            DEFAULT_WINDOWS_GECKODRIVER_VERSION
+        );
+        DEFAULT_WINDOWS_GECKODRIVER_VERSION.to_owned()
+    } else {
+        log::info!("[geckodriver] Looking up latest version of geckodriver...");
+        match stamps::read_stamps_file_to_json() {
+            Ok(json) => {
+                if should_load_geckodriver_version_from_stamp(&json) {
+                    stamps::get_stamp_value(GECKODRIVER_VERSION_STAMP, &json)
+                } else {
+                    fetch_and_save_version()
+                }
             }
+            Err(_) => fetch_and_save_version(),
         }
-        Err(_) => fetch_and_save_version(),
-    }
-    .unwrap_or_else(|error| {
-        log::warn!(
-            "Cannot load or fetch geckodriver's latest version data, \
-             the default version {} will be used. Error: {}",
-            DEFAULT_GECKODRIVER_VERSION,
-            error
-        );
-        DEFAULT_GECKODRIVER_VERSION.to_owned()
-    });
-    assemble_geckodriver_url(&geckodriver_version, target, ext)
+        .unwrap_or_else(|error| {
+            log::warn!(
+                "[geckodriver] Cannot load or fetch geckodriver's latest version data, \
+                 the default version {} will be used. Error: {}",
+                DEFAULT_GECKODRIVER_VERSION,
+                error
+            );
+            DEFAULT_GECKODRIVER_VERSION.to_owned()
+        })
+    };
+    let url = assemble_geckodriver_url(&geckodriver_version, target, ext);
+    log::info!("[geckodriver] Fetching geckodriver at {}", url);
+    url
 }
 
 // ------ `get_geckodriver_url` helpers  ------