fix strict countryCode problem

lib/src/easy_localization_controller.dart

@@ -72,14 +72,29 @@ class EasyLocalizationController extends ChangeNotifier {
   }) {
     final selectedLocale = supportedLocales.firstWhere(
       (locale) => locale.supports(deviceLocale),
-      orElse: () => _getFallbackLocale(supportedLocales, fallbackLocale),
+      orElse: () => _getFallbackLocale(
+        supportedLocales,
+        fallbackLocale,
+        deviceLocale: deviceLocale,
+      ),
     );
     return selectedLocale;
   }
 
   //Get fallback Locale
   static Locale _getFallbackLocale(
-      List<Locale> supportedLocales, Locale? fallbackLocale) {
+      List<Locale> supportedLocales, Locale? fallbackLocale,
+      {final Locale? deviceLocale}) {
+    if (deviceLocale != null) {
+      // a locale that matches the language code of the device locale is
+      // preferred over the fallback locale
+      final deviceLanguage = deviceLocale.languageCode;
+      for (Locale locale in supportedLocales) {
+        if (locale.languageCode == deviceLanguage) {
+          return locale;
+        }
+      }
+    }
     //If fallbackLocale not set then return first from supportedLocales
     if (fallbackLocale != null) {
       return fallbackLocale;

test/easy_localization_test.dart

@@ -225,6 +225,36 @@ void main() {
           zhHans,
         );
       });
+
+      test('select best lenguage match if no perfect match exists', () { // #674
+        const userDeviceLocale = Locale('en', 'FR');
+        const supportedLocale1 = Locale('en', 'US');
+        const supportedLocale2 = Locale('zh', 'CN');
+
+        expect(
+          EasyLocalizationController.selectLocaleFrom(
+            [supportedLocale1, supportedLocale2],
+            userDeviceLocale,
+            fallbackLocale: supportedLocale2,
+          ),
+          supportedLocale1,
+        );
+      });
+
+      test('select perfect match if exists', () { // #674
+        const userDeviceLocale = Locale('en', 'GB');
+        const supportedLocale1 = Locale('en', 'US');
+        const supportedLocale2 = userDeviceLocale;
+
+        expect(
+          EasyLocalizationController.selectLocaleFrom(
+            [supportedLocale1, supportedLocale2],
+            userDeviceLocale,
+            fallbackLocale: supportedLocale2,
+          ),
+          supportedLocale2,
+        );
+      });
     });
 
     group('tr', () {