[gen_l10n] Support string list as preferred-supported-locales (#63649)

* [gen_l10n] Support string list as preferred-supported-locales, as documented.

* [gen_l10n] Convert preferredSupportedLocale to a list of strings. 

* [gen_l10n] Accept a multi option instead of a json string in the command line.

packages/flutter_tools/lib/src/build_system/targets/localizations.dart

@@ -56,7 +56,7 @@ void generateLocalizations({
         templateArbFileName: templateArbFileName,
         outputFileString: outputFileString,
         classNameString: options.outputClass ?? 'AppLocalizations',
-        preferredSupportedLocaleString: options.preferredSupportedLocales,
+        preferredSupportedLocale: options.preferredSupportedLocales,
         headerString: options.header,
         headerFile: options?.headerFile?.toFilePath(),
         useDeferredLoading: options.deferredLoading ?? false,
@@ -193,7 +193,7 @@ class LocalizationOptions {
   final String outputClass;
 
   /// The `--preferred-supported-locales` argument.
-  final String preferredSupportedLocales;
+  final List<String> preferredSupportedLocales;
 
   /// The `--header-file` argument.
   ///
@@ -240,7 +240,7 @@ LocalizationOptions parseLocalizationsOptions({
     untranslatedMessagesFile: _tryReadUri(yamlMap, 'untranslated-messages-file', logger),
     header: _tryReadString(yamlMap, 'header', logger),
     outputClass: _tryReadString(yamlMap, 'output-class', logger),
-    preferredSupportedLocales: _tryReadString(yamlMap, 'preferred-supported-locales', logger),
+    preferredSupportedLocales: _tryReadStringList(yamlMap, 'preferred-supported-locales', logger),
     headerFile: _tryReadUri(yamlMap, 'header-file', logger),
     deferredLoading: _tryReadBool(yamlMap, 'use-deferred-loading', logger),
     useSyntheticPackage: _tryReadBool(yamlMap, 'synthetic-package', logger) ?? true,
@@ -273,6 +273,21 @@ String _tryReadString(YamlMap yamlMap, String key, Logger logger) {
   return value as String;
 }
 
+List<String> _tryReadStringList(YamlMap yamlMap, String key, Logger logger) {
+  final Object value = yamlMap[key];
+  if (value == null) {
+    return null;
+  }
+  if (value is String) {
+    return <String>[value];
+  }
+  if (value is Iterable) {
+    return value.map((dynamic e) => e.toString()).toList();
+  }
+  logger.printError('"$value" must be String or List.');
+  throw Exception();
+}
+
 // Try to read a valid `Uri` or null from `yamlMap`, otherwise throw.
 Uri _tryReadUri(YamlMap yamlMap, String key, Logger logger) {
   final String value = _tryReadString(yamlMap, key, logger);

packages/flutter_tools/lib/src/commands/generate_localizations.dart

@@ -65,14 +65,16 @@ class GenerateLocalizationsCommand extends FlutterCommand {
       help: 'The Dart class name to use for the output localization and '
         'localizations delegate classes.',
     );
-    argParser.addOption(
+    argParser.addMultiOption(
       'preferred-supported-locales',
+      valueHelp: 'locale',
       help: 'The list of preferred supported locales for the application. '
         'By default, the tool will generate the supported locales list in '
         'alphabetical order. Use this flag if you would like to default to '
         'a different locale. \n\n'
-        "For example, pass in ['en_US'] if you would like your app to "
-        'default to American English if a device supports it.',
+        'For example, pass in `en_US` if you would like your app to '
+        'default to American English if a device supports it.'
+        '(Pass this option multiple times for defining multiple items',
     );
     argParser.addOption(
       'header',
@@ -169,7 +171,7 @@ class GenerateLocalizationsCommand extends FlutterCommand {
     final String templateArbFileName = stringArg('template-arb-file');
     final String untranslatedMessagesFile = stringArg('untranslated-messages-file');
     final String classNameString = stringArg('output-class');
-    final String preferredSupportedLocaleString = stringArg('preferred-supported-locales');
+    final List<String> preferredSupportedLocale = stringsArg('preferred-supported-locales');
     final String headerString = stringArg('header');
     final String headerFile = stringArg('header-file');
     final bool useDeferredLoading = boolArg('use-deferred-loading');
@@ -187,7 +189,7 @@ class GenerateLocalizationsCommand extends FlutterCommand {
           templateArbFileName: templateArbFileName,
           outputFileString: outputFileString,
           classNameString: classNameString,
-          preferredSupportedLocaleString: preferredSupportedLocaleString,
+          preferredSupportedLocale: preferredSupportedLocale,
           headerString: headerString,
           headerFile: headerFile,
           useDeferredLoading: useDeferredLoading,

packages/flutter_tools/lib/src/localizations/gen_l10n.dart

@@ -530,7 +530,7 @@ class LocalizationsGenerator {
     String templateArbFileName,
     String outputFileString,
     String classNameString,
-    String preferredSupportedLocaleString,
+    List<String> preferredSupportedLocale,
     String headerString,
     String headerFile,
     bool useDeferredLoading = false,
@@ -546,7 +546,7 @@ class LocalizationsGenerator {
     );
     setTemplateArbFile(templateArbFileName);
     setBaseOutputFile(outputFileString);
-    setPreferredSupportedLocales(preferredSupportedLocaleString);
+    setPreferredSupportedLocales(preferredSupportedLocale);
     _setHeader(headerString, headerFile);
     _setUseDeferredLoading(useDeferredLoading);
     className = classNameString;
@@ -707,18 +707,12 @@ class LocalizationsGenerator {
   /// Sets [preferredSupportedLocales] so that this particular list of locales
   /// will take priority over the other locales.
   @visibleForTesting
-  void setPreferredSupportedLocales(String inputLocales) {
-    if (inputLocales == null || inputLocales.trim().isEmpty) {
+  void setPreferredSupportedLocales(List<String> inputLocales) {
+    if (inputLocales == null || inputLocales.isEmpty) {
       _preferredSupportedLocales = const <LocaleInfo>[];
     } else {
-      final List<dynamic> preferredLocalesStringList = json.decode(inputLocales) as List<dynamic>;
-      _preferredSupportedLocales = preferredLocalesStringList.map((dynamic localeString) {
-        if (localeString.runtimeType != String) {
-          throw L10nException('Incorrect runtime type for $localeString');
-        }
-        return LocaleInfo.fromString(
-          localeString.toString(),
-        );
+      _preferredSupportedLocales = inputLocales.map((String localeString) {
+        return LocaleInfo.fromString(localeString);
       }).toList();
     }
   }

packages/flutter_tools/test/general.shard/build_system/targets/localizations_test.dart

@@ -35,7 +35,7 @@ void main() {
       deferredLoading: true,
       outputClass: 'Foo',
       outputLocalizationsFile: Uri.file('bar'),
-      preferredSupportedLocales: 'en_US',
+      preferredSupportedLocales: <String>['en_US'],
       templateArbFile: Uri.file('example.arb'),
       untranslatedMessagesFile: Uri.file('untranslated'),
       useSyntheticPackage: false,
@@ -57,7 +57,7 @@ void main() {
       templateArbFileName: 'example.arb',
       outputFileString: 'bar',
       classNameString: 'Foo',
-      preferredSupportedLocaleString: 'en_US',
+      preferredSupportedLocale: <String>['en_US'],
       headerString: 'HEADER',
       headerFile: 'header',
       useDeferredLoading: true,
@@ -92,7 +92,7 @@ flutter:
       deferredLoading: true,
       outputClass: 'Foo',
       outputLocalizationsFile: Uri.file('bar'),
-      preferredSupportedLocales: 'en_US',
+      preferredSupportedLocales: <String>['en_US'],
       templateArbFile: Uri.file('example.arb'),
       untranslatedMessagesFile: Uri.file('untranslated'),
       // Set synthetic package to true.
@@ -161,13 +161,28 @@ preferred-supported-locales: en_US
     expect(options.headerFile, Uri.parse('header'));
     expect(options.header, 'HEADER');
     expect(options.deferredLoading, true);
-    expect(options.preferredSupportedLocales, 'en_US');
+    expect(options.preferredSupportedLocales, <String>['en_US']);
   });
 
-  testWithoutContext('parseLocalizationsOptions throws exception on invalid yaml configuration', () async {
+  testWithoutContext('parseLocalizationsOptions handles preferredSupportedLocales as list', () async {
     final FileSystem fileSystem = MemoryFileSystem.test();
-    final File configFile = fileSystem.file('l10n.yaml')
-      ..writeAsStringSync('''
+    final File configFile = fileSystem.file('l10n.yaml')..writeAsStringSync('''
+preferred-supported-locales: ['en_US', 'de']
+''');
+
+    final LocalizationOptions options = parseLocalizationsOptions(
+      file: configFile,
+      logger: BufferLogger.test(),
+    );
+
+    expect(options.preferredSupportedLocales, <String>['en_US', 'de']);
+  });
+
+  testWithoutContext(
+      'parseLocalizationsOptions throws exception on invalid yaml configuration',
+      () async {
+    final FileSystem fileSystem = MemoryFileSystem.test();
+    final File configFile = fileSystem.file('l10n.yaml')..writeAsStringSync('''
 use-deferred-loading: string
 ''');
 

packages/flutter_tools/test/general.shard/generate_localizations_test.dart

@@ -793,7 +793,7 @@ void main() {
       l10nDirectory.childFile('app_zh.arb')
         .writeAsStringSync(singleZhMessageArbFileString);
 
-      const String preferredSupportedLocaleString = '["zh", "es"]';
+      const List<String> preferredSupportedLocale = <String>['zh', 'es'];
       LocalizationsGenerator generator;
       try {
         generator = LocalizationsGenerator(fs);
@@ -803,7 +803,7 @@ void main() {
           templateArbFileName: defaultTemplateArbFileName,
           outputFileString: defaultOutputFileString,
           classNameString: defaultClassNameString,
-          preferredSupportedLocaleString: preferredSupportedLocaleString,
+          preferredSupportedLocale: preferredSupportedLocale,
         );
         generator.loadResources();
       } on L10nException catch (e) {
@@ -815,47 +815,6 @@ void main() {
       expect(generator.supportedLocales.elementAt(2), LocaleInfo.fromString('en'));
     });
 
-    test(
-      'throws an error attempting to add preferred locales '
-      'with incorrect runtime type',
-      () {
-        final Directory l10nDirectory = fs.currentDirectory.childDirectory('lib').childDirectory('l10n')
-          ..createSync(recursive: true);
-        l10nDirectory.childFile('app_en.arb')
-          .writeAsStringSync(singleMessageArbFileString);
-        l10nDirectory.childFile('app_es.arb')
-          .writeAsStringSync(singleEsMessageArbFileString);
-        l10nDirectory.childFile('app_zh.arb')
-          .writeAsStringSync(singleZhMessageArbFileString);
-
-        const String preferredSupportedLocaleString = '[44, "en"]';
-        LocalizationsGenerator generator;
-        try {
-          generator = LocalizationsGenerator(fs);
-          generator.initialize(
-            inputPathString: defaultL10nPathString,
-            outputPathString: defaultL10nPathString,
-            templateArbFileName: defaultTemplateArbFileName,
-            outputFileString: defaultOutputFileString,
-            classNameString: defaultClassNameString,
-            preferredSupportedLocaleString: preferredSupportedLocaleString,
-          );
-          generator.loadResources();
-        } on L10nException catch (e) {
-          expect(
-            e.message,
-            contains('Incorrect runtime type'),
-          );
-          return;
-        }
-
-        fail(
-          'Should fail since an incorrect runtime type was used '
-          'in the preferredSupportedLocales list.'
-        );
-      },
-    );
-
     test(
       'throws an error attempting to add preferred locales '
       'when there is no corresponding arb file for that '
@@ -870,7 +829,7 @@ void main() {
         l10nDirectory.childFile('app_zh.arb')
           .writeAsStringSync(singleZhMessageArbFileString);
 
-        const String preferredSupportedLocaleString = '["am", "es"]';
+        const List<String> preferredSupportedLocale = <String>['am', 'es'];
         LocalizationsGenerator generator;
         try {
           generator = LocalizationsGenerator(fs);
@@ -880,7 +839,7 @@ void main() {
             templateArbFileName: defaultTemplateArbFileName,
             outputFileString: defaultOutputFileString,
             classNameString: defaultClassNameString,
-            preferredSupportedLocaleString: preferredSupportedLocaleString,
+            preferredSupportedLocale: preferredSupportedLocale,
           );
           generator.loadResources();
         } on L10nException catch (e) {
@@ -1152,7 +1111,7 @@ void main() {
         ..childFile('app_zh.arb').writeAsStringSync(singleZhMessageArbFileString)
         ..childFile('app_es.arb').writeAsStringSync(singleEsMessageArbFileString);
 
-      const String preferredSupportedLocaleString = '["zh"]';
+      const List<String> preferredSupportedLocale = <String>['zh'];
       final LocalizationsGenerator generator = LocalizationsGenerator(fs);
       try {
         generator.initialize(
@@ -1161,7 +1120,7 @@ void main() {
           templateArbFileName: defaultTemplateArbFileName,
           outputFileString: defaultOutputFileString,
           classNameString: defaultClassNameString,
-          preferredSupportedLocaleString: preferredSupportedLocaleString,
+          preferredSupportedLocale: preferredSupportedLocale,
         );
         generator.loadResources();
         generator.writeOutputFiles();