Make resource attributes optional for simple cases (#68774)

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

@@ -61,6 +61,7 @@ void generateLocalizations({
         headerFile: options?.headerFile?.toFilePath(),
         useDeferredLoading: options.deferredLoading ?? false,
         useSyntheticPackage: options.useSyntheticPackage ?? true,
+        areResourceAttributesRequired: options.areResourceAttributesRequired ?? false,
       )
       ..loadResources()
       ..writeOutputFiles()
@@ -161,6 +162,7 @@ class LocalizationOptions {
     this.headerFile,
     this.deferredLoading,
     this.useSyntheticPackage = true,
+    this.areResourceAttributesRequired = false,
   }) : assert(useSyntheticPackage != null);
 
   /// The `--arb-dir` argument.
@@ -211,6 +213,12 @@ class LocalizationOptions {
   /// Whether to generate the Dart localization files in a synthetic package
   /// or in a custom directory.
   final bool useSyntheticPackage;
+
+  /// The `required-resource-attributes` argument.
+  ///
+  /// Whether to require all resource ids to contain a corresponding
+  /// resource attribute.
+  final bool areResourceAttributesRequired;
 }
 
 /// Parse the localizations configuration options from [file].
@@ -243,6 +251,7 @@ LocalizationOptions parseLocalizationsOptions({
     headerFile: _tryReadUri(yamlMap, 'header-file', logger),
     deferredLoading: _tryReadBool(yamlMap, 'use-deferred-loading', logger),
     useSyntheticPackage: _tryReadBool(yamlMap, 'synthetic-package', logger) ?? true,
+    areResourceAttributesRequired: _tryReadBool(yamlMap, 'required-resource-attributes', logger) ?? false,
   );
 }
 

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

@@ -150,6 +150,14 @@ class GenerateLocalizationsCommand extends FlutterCommand {
         '\n\n'
         'When null, the relative path to the present working directory will be used.'
     );
+    argParser.addFlag(
+      'required-resource-attributes',
+      help: 'Requires all resource ids to contain a corresponding resource attribute.\n\n'
+        'By default, simple messages will not require metadata, but it is highly '
+        'recommended as this provides context for the meaning of a message to '
+        'readers.\n\n'
+        'Resource attributes are still required for plural messages.'
+    );
   }
 
   final FileSystem _fileSystem;
@@ -178,6 +186,7 @@ class GenerateLocalizationsCommand extends FlutterCommand {
     final String inputsAndOutputsListPath = stringArg('gen-inputs-and-outputs-list');
     final bool useSyntheticPackage = boolArg('synthetic-package');
     final String projectPathString = stringArg('project-dir');
+    final bool areResourceAttributesRequired = boolArg('required-resource-attributes');
 
     final LocalizationsGenerator localizationsGenerator = LocalizationsGenerator(_fileSystem);
 
@@ -196,6 +205,7 @@ class GenerateLocalizationsCommand extends FlutterCommand {
           inputsAndOutputsListPath: inputsAndOutputsListPath,
           useSyntheticPackage: useSyntheticPackage,
           projectPathString: projectPathString,
+          areResourceAttributesRequired: areResourceAttributesRequired,
         )
         ..loadResources()
         ..writeOutputFiles()

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

@@ -526,6 +526,12 @@ class LocalizationsGenerator {
   List<String> _inputFileList;
   List<String> _outputFileList;
 
+  /// Whether or not resource attributes are required for each corresponding
+  /// resource id.
+  ///
+  /// Resource attributes provide metadata about the message.
+  bool _areResourceAttributesRequired;
+
   /// Initializes [inputDirectory], [outputDirectory], [templateArbFile],
   /// [outputFile] and [className].
   ///
@@ -547,6 +553,7 @@ class LocalizationsGenerator {
     String inputsAndOutputsListPath,
     bool useSyntheticPackage = true,
     String projectPathString,
+    bool areResourceAttributesRequired = false,
   }) {
     _useSyntheticPackage = useSyntheticPackage;
     setProjectDir(projectPathString);
@@ -559,6 +566,7 @@ class LocalizationsGenerator {
     _setUseDeferredLoading(useDeferredLoading);
     className = classNameString;
     _setInputsAndOutputsListFile(inputsAndOutputsListPath);
+    _areResourceAttributesRequired = areResourceAttributesRequired;
   }
 
   static bool _isNotReadable(FileStat fileStat) {
@@ -793,7 +801,9 @@ class LocalizationsGenerator {
   void loadResources() {
     final AppResourceBundle templateBundle = AppResourceBundle(templateArbFile);
     _templateArbLocale = templateBundle.locale;
-    _allMessages = templateBundle.resourceIds.map((String id) => Message(templateBundle.resources, id));
+    _allMessages = templateBundle.resourceIds.map((String id) => Message(
+      templateBundle.resources, id, _areResourceAttributesRequired,
+    ));
     for (final String resourceId in templateBundle.resourceIds) {
       if (!_isValidGetterAndMethodName(resourceId)) {
         throw L10nException(

packages/flutter_tools/lib/src/localizations/gen_l10n_types.dart

@@ -270,12 +270,12 @@ class Placeholder {
 // localized string to be shown for the template ARB file's locale.
 // The docs for the Placeholder explain how placeholder entries are defined.
 class Message {
-  Message(Map<String, dynamic> bundle, this.resourceId)
+  Message(Map<String, dynamic> bundle, this.resourceId, bool isResourceAttributeRequired)
     : assert(bundle != null),
       assert(resourceId != null && resourceId.isNotEmpty),
       value = _value(bundle, resourceId),
-      description = _description(bundle, resourceId),
-      placeholders = _placeholders(bundle, resourceId),
+      description = _description(bundle, resourceId, isResourceAttributeRequired),
+      placeholders = _placeholders(bundle, resourceId, isResourceAttributeRequired),
       _pluralMatch = _pluralRE.firstMatch(_value(bundle, resourceId));
 
   static final RegExp _pluralRE = RegExp(r'\s*\{([\w\s,]*),\s*plural\s*,');
@@ -312,25 +312,51 @@ class Message {
     return bundle[resourceId] as String;
   }
 
-  static Map<String, dynamic> _attributes(Map<String, dynamic> bundle, String resourceId) {
+  static Map<String, dynamic> _attributes(
+    Map<String, dynamic> bundle,
+    String resourceId,
+    bool isResourceAttributeRequired,
+  ) {
     final dynamic attributes = bundle['@$resourceId'];
-    if (attributes == null) {
-      throw L10nException(
-        'Resource attribute "@$resourceId" was not found. Please '
-        'ensure that each resource has a corresponding @resource.'
-      );
+    if (isResourceAttributeRequired) {
+      if (attributes == null) {
+        throw L10nException(
+          'Resource attribute "@$resourceId" was not found. Please '
+          'ensure that each resource has a corresponding @resource.'
+        );
+      }
     }
-    if (attributes is! Map<String, dynamic>) {
+
+    if (attributes != null && attributes is! Map<String, dynamic>) {
       throw L10nException(
         'The resource attribute "@$resourceId" is not a properly formatted Map. '
         'Ensure that it is a map with keys that are strings.'
       );
     }
+
+    final RegExpMatch pluralRegExp = _pluralRE.firstMatch(_value(bundle, resourceId));
+    final bool isPlural = pluralRegExp != null && pluralRegExp.groupCount == 1;
+    if (attributes == null && isPlural) {
+      throw L10nException(
+        'Resource attribute "@$resourceId" was not found. Please '
+        'ensure that plural resources have a corresponding @resource.'
+      );
+    }
+
     return attributes as Map<String, dynamic>;
   }
 
-  static String _description(Map<String, dynamic> bundle, String resourceId) {
-    final dynamic value = _attributes(bundle, resourceId)['description'];
+  static String _description(
+    Map<String, dynamic> bundle,
+    String resourceId,
+    bool isResourceAttributeRequired,
+  ) {
+    final Map<String, dynamic> resourceAttributes = _attributes(bundle, resourceId, isResourceAttributeRequired);
+    if (resourceAttributes == null) {
+      return null;
+    }
+
+    final dynamic value = resourceAttributes['description'];
     if (value == null) {
       return null;
     }
@@ -342,8 +368,16 @@ class Message {
     return value as String;
   }
 
-  static List<Placeholder> _placeholders(Map<String, dynamic> bundle, String resourceId) {
-    final dynamic value = _attributes(bundle, resourceId)['placeholders'];
+  static List<Placeholder> _placeholders(
+    Map<String, dynamic> bundle,
+    String resourceId,
+    bool isResourceAttributeRequired,
+  ) {
+    final Map<String, dynamic> resourceAttributes = _attributes(bundle, resourceId, isResourceAttributeRequired);
+    if (resourceAttributes == null) {
+      return <Placeholder>[];
+    }
+    final dynamic value = resourceAttributes['placeholders'];
     if (value == null) {
       return <Placeholder>[];
     }

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

@@ -39,6 +39,7 @@ void main() {
       templateArbFile: Uri.file('example.arb'),
       untranslatedMessagesFile: Uri.file('untranslated'),
       useSyntheticPackage: false,
+      areResourceAttributesRequired: true,
     );
 
     final LocalizationsGenerator mockLocalizationsGenerator = MockLocalizationsGenerator();
@@ -52,18 +53,19 @@ void main() {
 
     verify(
       mockLocalizationsGenerator.initialize(
-      inputPathString: 'arb',
-      outputPathString: null,
-      templateArbFileName: 'example.arb',
-      outputFileString: 'bar',
-      classNameString: 'Foo',
-      preferredSupportedLocale: <String>['en_US'],
-      headerString: 'HEADER',
-      headerFile: 'header',
-      useDeferredLoading: true,
-      inputsAndOutputsListPath: '/',
-      useSyntheticPackage: false,
-      projectPathString: '/',
+        inputPathString: 'arb',
+        outputPathString: null,
+        templateArbFileName: 'example.arb',
+        outputFileString: 'bar',
+        classNameString: 'Foo',
+        preferredSupportedLocale: <String>['en_US'],
+        headerString: 'HEADER',
+        headerFile: 'header',
+        useDeferredLoading: true,
+        inputsAndOutputsListPath: '/',
+        useSyntheticPackage: false,
+        projectPathString: '/',
+        areResourceAttributesRequired: true,
       ),
     ).called(1);
     verify(mockLocalizationsGenerator.loadResources()).called(1);

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

@@ -1587,7 +1587,7 @@ import 'output-localization-file_en.dart' deferred as output-localization-file_e
       },
     );
 
-    test('should throw when resource is missing resource attribute', () {
+    test('should throw when resource is missing resource attribute (isResourceAttributeRequired = true)', () {
       const String arbFileWithMissingResourceAttribute = '''
 {
   "title": "Stocks"
@@ -1605,6 +1605,7 @@ import 'output-localization-file_en.dart' deferred as output-localization-file_e
           templateArbFileName: defaultTemplateArbFileName,
           outputFileString: defaultOutputFileString,
           classNameString: defaultClassNameString,
+          areResourceAttributesRequired: true,
         );
         generator.loadResources();
         generator.writeOutputFiles();