Script to generate missing localization resources (#49379)

Added a new script to generate missing localizations for use when adding new localizations to the Flutter framework.

dev/tools/localization/bin/gen_missing_localizations.dart

+// Copyright 2014 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// This program updates the language locale arb files with any missing resource
+// entries that are included in the English arb files. This is useful when
+// adding new resources for localization. You can just add the appropriate
+// entries to the English arb file and then run this script. It will then check
+// all of the other language locale arb files and update them with new 'TBD'
+// entries for any missing resources. These will be picked up by the localization
+// team and then translated.
+//
+// ## Usage
+//
+// Run this program from the root of the git repository.
+//
+// ```
+// dart dev/tools/localization/bin/gen_missing_localizations.dart
+// ```
+
+import 'dart:convert';
+import 'dart:io';
+
+import 'package:path/path.dart' as path;
+
+import '../localizations_utils.dart';
+import '../localizations_validator.dart';
+
+Future<void> main(List<String> rawArgs) async {
+  checkCwdIsRepoRoot('gen_missing_localizations');
+
+  final String localizationPath = path.join('packages', 'flutter_localizations', 'lib', 'src', 'l10n');
+  updateMissingResources(localizationPath, 'material');
+  updateMissingResources(localizationPath, 'cupertino');
+}
+
+Map<String, dynamic> loadBundle(File file) {
+  if (!FileSystemEntity.isFileSync(file.path))
+    exitWithError('Unable to find input file: ${file.path}');
+  return json.decode(file.readAsStringSync()) as Map<String, dynamic>;
+}
+
+void writeBundle(File file, Map<String, dynamic> bundle) {
+  final StringBuffer contents = StringBuffer();
+  contents.writeln('{');
+  for (final String key in bundle.keys) {
+    contents.writeln('  "$key": ${json.encode(bundle[key])}${key == bundle.keys.last ? '' : ','}');
+  }
+  contents.writeln('}');
+  file.writeAsStringSync(contents.toString());
+}
+
+Set<String> resourceKeys(Map<String, dynamic> bundle) {
+  return Set<String>.from(
+    // Skip any attribute keys
+    bundle.keys.where((String key) => !key.startsWith('@'))
+  );
+}
+
+bool intentionallyOmitted(String key, Map<String, dynamic> bundle) {
+  final String attributeKey = '@$key';
+  final dynamic attribute = bundle[attributeKey];
+  return attribute is Map && attribute.containsKey('notUsed');
+}
+
+/// Whether `key` corresponds to one of the plural variations of a key with
+/// the same prefix and suffix "Other".
+bool isPluralVariation(String key, Map<String, dynamic> bundle) {
+  final Match pluralMatch = kPluralRegexp.firstMatch(key);
+  if (pluralMatch == null)
+    return false;
+  final String prefix = pluralMatch[1];
+  return bundle.containsKey('${prefix}Other');
+}
+
+void updateMissingResources(String localizationPath, String groupPrefix) {
+  final Directory localizationDir = Directory(localizationPath);
+  final RegExp filenamePattern = RegExp('${groupPrefix}_(\\w+)\.arb');
+
+  final Set<String> requiredKeys = resourceKeys(loadBundle(File(path.join(localizationPath, '${groupPrefix}_en.arb'))));
+
+  for (final FileSystemEntity entity in localizationDir.listSync().toList()..sort(sortFilesByPath)) {
+    final String entityPath = entity.path;
+    if (FileSystemEntity.isFileSync(entityPath) && filenamePattern.hasMatch(entityPath)) {
+      final String localeString = filenamePattern.firstMatch(entityPath)[1];
+      final LocaleInfo locale = LocaleInfo.fromString(localeString);
+
+      // Only look at top-level language locales
+      if (locale.length == 1) {
+        final File arbFile = File(entityPath);
+        final Map<String, dynamic> localeBundle = loadBundle(arbFile);
+        final Set<String> localeResources = resourceKeys(localeBundle);
+        final Set<String> missingResources = requiredKeys.difference(localeResources).where(
+          (String key) => !isPluralVariation(key, localeBundle) && !intentionallyOmitted(key, localeBundle)
+        ).toSet();
+        if (missingResources.isNotEmpty) {
+          localeBundle.addEntries(missingResources.map((String k) => MapEntry<String, String>(k, 'TBD')));
+          writeBundle(arbFile, localeBundle);
+          print('Updated $entityPath with missing entries for $missingResources');
+        }
+      }
+    }
+  }
+}

packages/flutter/lib/src/material/material_localizations.dart

@@ -27,11 +27,19 @@ import 'typography.dart';
 //
 // 4. Update the flutter_localizations package. To add a new string to the
 //    flutter_localizations package, you must first add it to the English
-//    translations (lib/src/l10n/material_en.arb), including a description, then
-//    you must add it to every other language (all the other *.arb files in that
-//    same directory), listing the translation as `TBD`. After that you have to
-//    re-generate lib/src/l10n/localizations.dart by running
-//    `dart dev/tools/localization/bin/gen_localizations.dart --overwrite`.
+//    translations (lib/src/l10n/material_en.arb), including a description.
+//
+//    Then you need to add  new `TBD` entries for the string to all of the other
+//    language locale files by running:
+//    ```
+//    dart dev/tools/localization/bin/gen_missing_localizations.dart
+//    ```
+//
+//    Finally you need to re-generate lib/src/l10n/localizations.dart by running:
+//    ```
+//    dart dev/tools/localization/bin/gen_localizations.dart --overwrite
+//    ```
+//
 //    There is a README file with further information in the lib/src/l10n/
 //    directory.
 //