Migrate localizations_utils to null safety (#78939)

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

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:meta/meta.dart';
 import 'package:yaml/yaml.dart';
 
@@ -22,11 +20,11 @@ int sortFilesByPath (File a, File b) {
 @immutable
 class LocaleInfo implements Comparable<LocaleInfo> {
   const LocaleInfo({
-    this.languageCode,
-    this.scriptCode,
-    this.countryCode,
-    this.length,
-    this.originalString,
+    required this.languageCode,
+    required this.scriptCode,
+    required this.countryCode,
+    required this.length,
+    required this.originalString,
   });
 
   /// Simple parser. Expects the locale string to be in the form of 'language_script_COUNTRY'
@@ -41,8 +39,8 @@ class LocaleInfo implements Comparable<LocaleInfo> {
     final List<String> codes = locale.split('_'); // [language, script, country]
     assert(codes.isNotEmpty && codes.length < 4);
     final String languageCode = codes[0];
-    String scriptCode;
-    String countryCode;
+    String? scriptCode;
+    String? countryCode;
     int length = codes.length;
     String originalString = locale;
     if (codes.length == 2) {
@@ -112,8 +110,8 @@ class LocaleInfo implements Comparable<LocaleInfo> {
   }
 
   final String languageCode;
-  final String scriptCode;
-  final String countryCode;
+  final String? scriptCode;
+  final String? countryCode;
   final int length;             // The number of fields. Ranges from 1-3.
   final String originalString;  // Original un-parsed locale string.
 
@@ -149,7 +147,7 @@ class LocaleInfo implements Comparable<LocaleInfo> {
 // See also //master/tools/gen_locale.dart in the engine repo.
 Map<String, List<String>> _parseSection(String section) {
   final Map<String, List<String>> result = <String, List<String>>{};
-  List<String> lastHeading;
+  late List<String> lastHeading;
   for (final String line in section.split('\n')) {
     if (line == '') {
       continue;
@@ -165,7 +163,7 @@ Map<String, List<String>> _parseSection(String section) {
     final String name = line.substring(0, colon);
     final String value = line.substring(colon + 2);
     lastHeading = result.putIfAbsent(name, () => <String>[]);
-    result[name].add(value);
+    result[name]!.add(value);
   }
   return result;
 }
@@ -184,11 +182,11 @@ void precacheLanguageAndRegionTags() {
       languageSubtagRegistry.split('%%').skip(1).map<Map<String, List<String>>>(_parseSection).toList();
   for (final Map<String, List<String>> section in sections) {
     assert(section.containsKey('Type'), section.toString());
-    final String type = section['Type'].single;
+    final String type = section['Type']!.single;
     if (type == 'language' || type == 'region' || type == 'script') {
       assert(section.containsKey('Subtag') && section.containsKey('Description'), section.toString());
-      final String subtag = section['Subtag'].single;
-      String description = section['Description'].join(' ');
+      final String subtag = section['Subtag']!.single;
+      String description = section['Description']!.join(' ');
       if (description.startsWith('United ')) {
         description = 'the $description';
       }
@@ -220,10 +218,10 @@ String describeLocale(String tag) {
   final List<String> subtags = tag.split('_');
   assert(subtags.isNotEmpty);
   assert(_languages.containsKey(subtags[0]));
-  final String language = _languages[subtags[0]];
+  final String language = _languages[subtags[0]]!;
   String output = language;
-  String region;
-  String script;
+  String? region;
+  String? script;
   if (subtags.length == 2) {
     region = _regions[subtags[1]];
     script = _scripts[subtags[1]];
@@ -311,50 +309,50 @@ class LocalizationOptions {
   /// The `--arb-dir` argument.
   ///
   /// The directory where all input localization files should reside.
-  final Uri arbDirectory;
+  final Uri? arbDirectory;
 
   /// The `--template-arb-file` argument.
   ///
   /// This URI is relative to [arbDirectory].
-  final Uri templateArbFile;
+  final Uri? templateArbFile;
 
   /// The `--output-localization-file` argument.
   ///
   /// This URI is relative to [arbDirectory].
-  final Uri outputLocalizationsFile;
+  final Uri? outputLocalizationsFile;
 
   /// The `--untranslated-messages-file` argument.
   ///
   /// This URI is relative to [arbDirectory].
-  final Uri untranslatedMessagesFile;
+  final Uri? untranslatedMessagesFile;
 
   /// The `--header` argument.
   ///
   /// The header to prepend to the generated Dart localizations.
-  final String header;
+  final String? header;
 
   /// The `--output-class` argument.
-  final String outputClass;
+  final String? outputClass;
 
   /// The `--output-dir` argument.
   ///
   /// The directory where all output localization files should be generated.
-  final Uri outputDirectory;
+  final Uri? outputDirectory;
 
   /// The `--preferred-supported-locales` argument.
-  final List<String> preferredSupportedLocales;
+  final List<String>? preferredSupportedLocales;
 
   /// The `--header-file` argument.
   ///
   /// A file containing the header to prepend to the generated
   /// Dart localizations.
-  final Uri headerFile;
+  final Uri? headerFile;
 
   /// The `--use-deferred-loading` argument.
   ///
   /// Whether to generate the Dart localization file with locales imported
   /// as deferred.
-  final bool deferredLoading;
+  final bool? deferredLoading;
 
   /// The `--synthetic-package` argument.
   ///
@@ -375,8 +373,8 @@ class LocalizationOptions {
 /// [LocalizationOptions] with all fields as `null` if the config file exists
 /// but is empty.
 LocalizationOptions parseLocalizationsOptions({
-  @required File file,
-  @required Logger logger,
+  required File file,
+  required Logger logger,
 }) {
   final String contents = file.readAsStringSync();
   if (contents.trim().isEmpty) {
@@ -387,26 +385,25 @@ LocalizationOptions parseLocalizationsOptions({
     logger.printError('Expected ${file.path} to contain a map, instead was $yamlNode');
     throw Exception();
   }
-  final YamlMap yamlMap = yamlNode as YamlMap;
   return LocalizationOptions(
-    arbDirectory: _tryReadUri(yamlMap, 'arb-dir', logger),
-    templateArbFile: _tryReadUri(yamlMap, 'template-arb-file', logger),
-    outputLocalizationsFile: _tryReadUri(yamlMap, 'output-localization-file', logger),
-    untranslatedMessagesFile: _tryReadUri(yamlMap, 'untranslated-messages-file', logger),
-    header: _tryReadString(yamlMap, 'header', logger),
-    outputClass: _tryReadString(yamlMap, 'output-class', logger),
-    outputDirectory: _tryReadUri(yamlMap, 'output-dir', 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,
-    areResourceAttributesRequired: _tryReadBool(yamlMap, 'required-resource-attributes', logger) ?? false,
+    arbDirectory: _tryReadUri(yamlNode, 'arb-dir', logger),
+    templateArbFile: _tryReadUri(yamlNode, 'template-arb-file', logger),
+    outputLocalizationsFile: _tryReadUri(yamlNode, 'output-localization-file', logger),
+    untranslatedMessagesFile: _tryReadUri(yamlNode, 'untranslated-messages-file', logger),
+    header: _tryReadString(yamlNode, 'header', logger),
+    outputClass: _tryReadString(yamlNode, 'output-class', logger),
+    outputDirectory: _tryReadUri(yamlNode, 'output-dir', logger),
+    preferredSupportedLocales: _tryReadStringList(yamlNode, 'preferred-supported-locales', logger),
+    headerFile: _tryReadUri(yamlNode, 'header-file', logger),
+    deferredLoading: _tryReadBool(yamlNode, 'use-deferred-loading', logger),
+    useSyntheticPackage: _tryReadBool(yamlNode, 'synthetic-package', logger) ?? true,
+    areResourceAttributesRequired: _tryReadBool(yamlNode, 'required-resource-attributes', logger) ?? false,
   );
 }
 
 // Try to read a `bool` value or null from `yamlMap`, otherwise throw.
-bool _tryReadBool(YamlMap yamlMap, String key, Logger logger) {
-  final Object value = yamlMap[key];
+bool? _tryReadBool(YamlMap yamlMap, String key, Logger logger) {
+  final Object? value = yamlMap[key];
   if (value == null) {
     return null;
   }
@@ -414,12 +411,12 @@ bool _tryReadBool(YamlMap yamlMap, String key, Logger logger) {
     logger.printError('Expected "$key" to have a bool value, instead was "$value"');
     throw Exception();
   }
-  return value as bool;
+  return value;
 }
 
 // Try to read a `String` value or null from `yamlMap`, otherwise throw.
-String _tryReadString(YamlMap yamlMap, String key, Logger logger) {
-  final Object value = yamlMap[key];
+String? _tryReadString(YamlMap yamlMap, String key, Logger logger) {
+  final Object? value = yamlMap[key];
   if (value == null) {
     return null;
   }
@@ -427,11 +424,11 @@ String _tryReadString(YamlMap yamlMap, String key, Logger logger) {
     logger.printError('Expected "$key" to have a String value, instead was "$value"');
     throw Exception();
   }
-  return value as String;
+  return value;
 }
 
-List<String> _tryReadStringList(YamlMap yamlMap, String key, Logger logger) {
-  final Object value = yamlMap[key];
+List<String>? _tryReadStringList(YamlMap yamlMap, String key, Logger logger) {
+  final Object? value = yamlMap[key];
   if (value == null) {
     return null;
   }
@@ -446,12 +443,12 @@ List<String> _tryReadStringList(YamlMap yamlMap, String key, Logger logger) {
 }
 
 // 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);
+Uri? _tryReadUri(YamlMap yamlMap, String key, Logger logger) {
+  final String? value = _tryReadString(yamlMap, key, logger);
   if (value == null) {
     return null;
   }
-  final Uri uri = Uri.tryParse(value);
+  final Uri? uri = Uri.tryParse(value);
   if (uri == null) {
     logger.printError('"$value" must be a relative file URI');
   }

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

@@ -19,7 +19,7 @@ import '../../../src/context.dart';
 void main() {
   // Verifies that values are correctly passed through the localizations
   // target, but does not validate them beyond the serialized data type.
-  testUsingContext('generateLocalizations forwards arguments correctly', () async {
+  testWithoutContext('generateLocalizations forwards arguments correctly', () async {
     final FileSystem fileSystem = MemoryFileSystem.test();
     final Logger logger = BufferLogger.test();
     final Directory flutterProjectDirectory = fileSystem
@@ -76,7 +76,7 @@ void main() {
     verify(mockLocalizationsGenerator.writeOutputFiles(logger, isFromYaml: true)).called(1);
   });
 
-  testUsingContext('generateLocalizations throws exception on missing flutter: generate: true flag', () async {
+  testWithoutContext('generateLocalizations throws exception on missing flutter: generate: true flag', () async {
     final FileSystem fileSystem = MemoryFileSystem.test();
     final BufferLogger logger = BufferLogger.test();
     final Directory arbDirectory = fileSystem.directory('arb')