feedback

lighthouse-core/config/config.js

@@ -407,15 +407,18 @@ class Config {
    * @return {LH.Config.Settings}
    */
   static initSettings(settingsJson = {}, flags) {
+    // Use locale specified in flags or settings, allowing i18n system to select fallback if needed.
+    const locale = i18n.lookupLocale((flags && flags.locale) || settingsJson.locale);
+
     // Fill in missing settings with defaults
     const {defaultSettings} = constants;
     const settingWithDefaults = merge(deepClone(defaultSettings), settingsJson, true);
 
     // Override any applicable settings with CLI flags
     const settingsWithFlags = merge(settingWithDefaults || {}, cleanFlagsForSettings(flags), true);
 
-    // Use locale specified in flags or settings, allowing i18n system to select fallback if needed.
-    settingsWithFlags.locale = i18n.lookupLocale((flags && flags.locale) || settingsJson.locale);
+    // Locale is special and comes only from flags/settings
+    settingsWithFlags.locale = locale;
 
     return settingsWithFlags;
   }

lighthouse-core/lib/i18n.js

@@ -68,14 +68,17 @@ const formats = {
 };
 
 /**
- * Look up the best available locale for the requested language, falling back by
- * looking at progressively shorter prefixes (`de-CH-1996` -> `de-CH` -> `de`),
- * and finally returning the default locale ('en-US') if no match is found.
+ * Look up the best available locale for the requested language through these fall backs:
+ * - exact match
+ * - progressively shorter prefixes (`de-CH-1996` -> `de-CH` -> `de`)
+ * - the default locale ('en-US') if no match is found
+ *
+ * If `locale` isn't provided, the default is used.
  * @param {string=} locale
  * @return {LH.Locale}
  */
-function lookupLocale(locale = MessageFormat.defaultLocale) {
-  // TODO: could do more work to sniff out defaultLocale
+function lookupLocale(locale) {
+  // TODO: could do more work to sniff out default locale
   const canonicalLocale = Intl.getCanonicalLocales(locale)[0];
 
   const closestLocale = lookupClosestLocale(canonicalLocale, LOCALES);

typings/externs.d.ts

@@ -18,7 +18,7 @@ declare global {
   // Augment Intl to include
   // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/getCanonicalLocales
   namespace Intl {
-    var getCanonicalLocales: (locales: string | Array<string>) => Array<string>;
+    var getCanonicalLocales: (locales?: string | Array<string>) => Array<string>;
   }
 
   /** Make properties K in T optional. */