packages/flutter_tools/lib/src/localizations/localizations_utils.dart - mirrors/flutter - Git at Google

 // 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.

 import 'package:meta/meta.dart';
 import 'package:yaml/yaml.dart';

 import '../base/file_system.dart';
 import '../base/logger.dart';
 import 'language_subtag_registry.dart';

 typedef HeaderGenerator = String Function(String regenerateInstructions);
 typedef ConstructorGenerator = String Function(LocaleInfo locale);

 int sortFilesByPath (File a, File b) {
   return a.path.compareTo(b.path);
 }

 /// Simple data class to hold parsed locale. Does not promise validity of any data.
 @immutable
 class LocaleInfo implements Comparable<LocaleInfo> {
   const LocaleInfo({
     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'
   /// where the language is 2 characters, script is 4 characters with the first uppercase,
   /// and country is 2-3 characters and all uppercase.
   ///
   /// 'language_COUNTRY' or 'language_script' are also valid. Missing fields will be null.
   ///
   /// When `deriveScriptCode` is true, if [scriptCode] was unspecified, it will
   /// be derived from the [languageCode] and [countryCode] if possible.
   factory LocaleInfo.fromString(String locale, { bool deriveScriptCode = false }) {
     final List<String> codes = locale.split('_'); // [language, script, country]
     assert(codes.isNotEmpty && codes.length < 4);
     final String languageCode = codes[0];
     String? scriptCode;
     String? countryCode;
     int length = codes.length;
     String originalString = locale;
     if (codes.length == 2) {
       scriptCode = codes[1].length >= 4 ? codes[1] : null;
       countryCode = codes[1].length < 4 ? codes[1] : null;
     } else if (codes.length == 3) {
       scriptCode = codes[1].length > codes[2].length ? codes[1] : codes[2];
       countryCode = codes[1].length < codes[2].length ? codes[1] : codes[2];
     }
     assert(codes[0] != null && codes[0].isNotEmpty);
     assert(countryCode == null || countryCode.isNotEmpty);
     assert(scriptCode == null || scriptCode.isNotEmpty);

     /// Adds scriptCodes to locales where we are able to assume it to provide
     /// finer granularity when resolving locales.
     ///
     /// The basis of the assumptions here are based off of known usage of scripts
     /// across various countries. For example, we know Taiwan uses traditional (Hant)
     /// script, so it is safe to apply (Hant) to Taiwanese languages.
     if (deriveScriptCode && scriptCode == null) {
       switch (languageCode) {
         case 'zh': {
           if (countryCode == null) {
             scriptCode = 'Hans';
           }
           switch (countryCode) {
             case 'CN':
             case 'SG':
               scriptCode = 'Hans';
               break;
             case 'TW':
             case 'HK':
             case 'MO':
               scriptCode = 'Hant';
               break;
           }
           break;
         }
         case 'sr': {
           if (countryCode == null) {
             scriptCode = 'Cyrl';
           }
           break;
         }
       }
       // Increment length if we were able to assume a scriptCode.
       if (scriptCode != null) {
         length += 1;
       }
       // Update the base string to reflect assumed scriptCodes.
       originalString = languageCode;
       if (scriptCode != null) {
         originalString += '_$scriptCode';
       }
       if (countryCode != null) {
         originalString += '_$countryCode';
       }
     }

     return LocaleInfo(
       languageCode: languageCode,
       scriptCode: scriptCode,
       countryCode: countryCode,
       length: length,
       originalString: originalString,
     );
   }

   final String languageCode;
   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.

   String camelCase() {
     return originalString
       .split('_')
       .map<String>((String part) => part.substring(0, 1).toUpperCase() + part.substring(1).toLowerCase())
       .join();
   }

   @override
   bool operator ==(Object other) {
     return other is LocaleInfo
         && other.originalString == originalString;
   }

   @override
   int get hashCode => originalString.hashCode;

   @override
   String toString() {
     return originalString;
   }

   @override
   int compareTo(LocaleInfo other) {
     return originalString.compareTo(other.originalString);
   }
 }

 // 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>>{};
   late List<String> lastHeading;
   for (final String line in section.split('\n')) {
     if (line == '') {
       continue;
     }
     if (line.startsWith('  ')) {
       lastHeading[lastHeading.length - 1] = '${lastHeading.last}${line.substring(1)}';
       continue;
     }
     final int colon = line.indexOf(':');
     if (colon <= 0) {
       throw 'not sure how to deal with "$line"';
     }
     final String name = line.substring(0, colon);
     final String value = line.substring(colon + 2);
     lastHeading = result.putIfAbsent(name, () => <String>[]);
     result[name]!.add(value);
   }
   return result;
 }

 final Map<String, String> _languages = <String, String>{};
 final Map<String, String> _regions = <String, String>{};
 final Map<String, String> _scripts = <String, String>{};
 const String kProvincePrefix = ', Province of ';
 const String kParentheticalPrefix = ' (';

 /// Prepares the data for the [describeLocale] method below.
 ///
 /// The data is obtained from the official IANA registry.
 void precacheLanguageAndRegionTags() {
   final List<Map<String, List<String>>> sections =
       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;
     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(' ');
       if (description.startsWith('United ')) {
         description = 'the $description';
       }
       if (description.contains(kParentheticalPrefix)) {
         description = description.substring(0, description.indexOf(kParentheticalPrefix));
       }
       if (description.contains(kProvincePrefix)) {
         description = description.substring(0, description.indexOf(kProvincePrefix));
       }
       if (description.endsWith(' Republic')) {
         description = 'the $description';
       }
       switch (type) {
         case 'language':
           _languages[subtag] = description;
           break;
         case 'region':
           _regions[subtag] = description;
           break;
         case 'script':
           _scripts[subtag] = description;
           break;
       }
     }
   }
 }

 String describeLocale(String tag) {
   final List<String> subtags = tag.split('_');
   assert(subtags.isNotEmpty);
   assert(_languages.containsKey(subtags[0]));
   final String language = _languages[subtags[0]]!;
   String output = language;
   String? region;
   String? script;
   if (subtags.length == 2) {
     region = _regions[subtags[1]];
     script = _scripts[subtags[1]];
     assert(region != null || script != null);
   } else if (subtags.length >= 3) {
     region = _regions[subtags[2]];
     script = _scripts[subtags[1]];
     assert(region != null && script != null);
   }
   if (region != null) {
     output += ', as used in $region';
   }
   if (script != null) {
     output += ', using the $script script';
   }
   return output;
 }

 /// Return the input string as a Dart-parsable string.
 ///
 /// ```
 /// foo => 'foo'
 /// foo "bar" => 'foo "bar"'
 /// foo 'bar' => "foo 'bar'"
 /// foo 'bar' "baz" => '''foo 'bar' "baz"'''
 /// ```
 ///
 /// This function is used by tools that take in a JSON-formatted file to
 /// generate Dart code. For this reason, characters with special meaning
 /// in JSON files are escaped. For example, the backspace character (\b)
 /// has to be properly escaped by this function so that the generated
 /// Dart code correctly represents this character:
 /// ```
 /// foo\bar => 'foo\\bar'
 /// foo\nbar => 'foo\\nbar'
 /// foo\\nbar => 'foo\\\\nbar'
 /// foo\\bar => 'foo\\\\bar'
 /// foo\ bar => 'foo\\ bar'
 /// foo$bar = 'foo\$bar'
 /// ```
 String generateString(String value) {
   const String backslash = '__BACKSLASH__';
   assert(
     !value.contains(backslash),
     'Input string cannot contain the sequence: '
     '"__BACKSLASH__", as it is used as part of '
     'backslash character processing.'
   );

   value = value
     // Replace backslashes with a placeholder for now to properly parse
     // other special characters.
     .replaceAll(r'\', backslash)
     .replaceAll(r'$', r'\$')
     .replaceAll("'", r"\'")
     .replaceAll('"', r'\"')
     .replaceAll('\n', r'\n')
     .replaceAll('\f', r'\f')
     .replaceAll('\t', r'\t')
     .replaceAll('\r', r'\r')
     .replaceAll('\b', r'\b')
     // Reintroduce escaped backslashes into generated Dart string.
     .replaceAll(backslash, r'\\');

   return "'$value'";
 }

 /// Typed configuration from the localizations config file.
 class LocalizationOptions {
   const LocalizationOptions({
     this.arbDirectory,
     this.templateArbFile,
     this.outputLocalizationsFile,
     this.untranslatedMessagesFile,
     this.header,
     this.outputClass,
     this.outputDirectory,
     this.preferredSupportedLocales,
     this.headerFile,
     this.deferredLoading,
     this.useSyntheticPackage = true,
     this.areResourceAttributesRequired = false,
     this.usesNullableGetter = true,
   }) : assert(useSyntheticPackage != null);

   /// The `--arb-dir` argument.
   ///
   /// The directory where all input localization files should reside.
   final Uri? arbDirectory;

   /// The `--template-arb-file` argument.
   ///
   /// This URI is relative to [arbDirectory].
   final Uri? templateArbFile;

   /// The `--output-localization-file` argument.
   ///
   /// This URI is relative to [arbDirectory].
   final Uri? outputLocalizationsFile;

   /// The `--untranslated-messages-file` argument.
   ///
   /// This URI is relative to [arbDirectory].
   final Uri? untranslatedMessagesFile;

   /// The `--header` argument.
   ///
   /// The header to prepend to the generated Dart localizations.
   final String? header;

   /// The `--output-class` argument.
   final String? outputClass;

   /// The `--output-dir` argument.
   ///
   /// The directory where all output localization files should be generated.
   final Uri? outputDirectory;

   /// The `--preferred-supported-locales` argument.
   final List<String>? preferredSupportedLocales;

   /// The `--header-file` argument.
   ///
   /// A file containing the header to prepend to the generated
   /// Dart localizations.
   final Uri? headerFile;

   /// The `--use-deferred-loading` argument.
   ///
   /// Whether to generate the Dart localization file with locales imported
   /// as deferred.
   final bool? deferredLoading;

   /// The `--synthetic-package` argument.
   ///
   /// 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;

   /// The `nullable-getter` argument.
   ///
   /// Whether or not the localizations class getter is nullable.
   final bool usesNullableGetter;
 }

 /// Parse the localizations configuration options from [file].
 ///
 /// Throws [Exception] if any of the contents are invalid. Returns a
 /// [LocalizationOptions] with all fields as `null` if the config file exists
 /// but is empty.
 LocalizationOptions parseLocalizationsOptions({
   required File file,
   required Logger logger,
 }) {
   final String contents = file.readAsStringSync();
   if (contents.trim().isEmpty) {
     return const LocalizationOptions();
   }
   final YamlNode yamlNode = loadYamlNode(file.readAsStringSync());
   if (yamlNode is! YamlMap) {
     logger.printError('Expected ${file.path} to contain a map, instead was $yamlNode');
     throw Exception();
   }
   return LocalizationOptions(
     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,
     usesNullableGetter: _tryReadBool(yamlNode, 'nullable-getter', logger) ?? true,
   );
 }

 // 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];
   if (value == null) {
     return null;
   }
   if (value is! bool) {
     logger.printError('Expected "$key" to have a bool value, instead was "$value"');
     throw Exception();
   }
   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];
   if (value == null) {
     return null;
   }
   if (value is! String) {
     logger.printError('Expected "$key" to have a String value, instead was "$value"');
     throw Exception();
   }
   return value;
 }

 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);
   if (value == null) {
     return null;
   }
   final Uri? uri = Uri.tryParse(value);
   if (uri == null) {
     logger.printError('"$value" must be a relative file URI');
   }
   return uri;
 }
	// 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.

	import 'package:meta/meta.dart';
	import 'package:yaml/yaml.dart';

	import '../base/file_system.dart';
	import '../base/logger.dart';
	import 'language_subtag_registry.dart';

	typedef HeaderGenerator = String Function(String regenerateInstructions);
	typedef ConstructorGenerator = String Function(LocaleInfo locale);

	int sortFilesByPath (File a, File b) {
	return a.path.compareTo(b.path);
	}

	/// Simple data class to hold parsed locale. Does not promise validity of any data.
	@immutable
	class LocaleInfo implements Comparable<LocaleInfo> {
	const LocaleInfo({
	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'
	/// where the language is 2 characters, script is 4 characters with the first uppercase,
	/// and country is 2-3 characters and all uppercase.
	///
	/// 'language_COUNTRY' or 'language_script' are also valid. Missing fields will be null.
	///
	/// When `deriveScriptCode` is true, if [scriptCode] was unspecified, it will
	/// be derived from the [languageCode] and [countryCode] if possible.
	factory LocaleInfo.fromString(String locale, { bool deriveScriptCode = false }) {
	final List<String> codes = locale.split('_'); // [language, script, country]
	assert(codes.isNotEmpty && codes.length < 4);
	final String languageCode = codes[0];
	String? scriptCode;
	String? countryCode;
	int length = codes.length;
	String originalString = locale;
	if (codes.length == 2) {
	scriptCode = codes[1].length >= 4 ? codes[1] : null;
	countryCode = codes[1].length < 4 ? codes[1] : null;
	} else if (codes.length == 3) {
	scriptCode = codes[1].length > codes[2].length ? codes[1] : codes[2];
	countryCode = codes[1].length < codes[2].length ? codes[1] : codes[2];
	}
	assert(codes[0] != null && codes[0].isNotEmpty);
	assert(countryCode == null \|\| countryCode.isNotEmpty);
	assert(scriptCode == null \|\| scriptCode.isNotEmpty);

	/// Adds scriptCodes to locales where we are able to assume it to provide
	/// finer granularity when resolving locales.
	///
	/// The basis of the assumptions here are based off of known usage of scripts
	/// across various countries. For example, we know Taiwan uses traditional (Hant)
	/// script, so it is safe to apply (Hant) to Taiwanese languages.
	if (deriveScriptCode && scriptCode == null) {
	switch (languageCode) {
	case 'zh': {
	if (countryCode == null) {
	scriptCode = 'Hans';
	}
	switch (countryCode) {
	case 'CN':
	case 'SG':
	scriptCode = 'Hans';
	break;
	case 'TW':
	case 'HK':
	case 'MO':
	scriptCode = 'Hant';
	break;
	}
	break;
	}
	case 'sr': {
	if (countryCode == null) {
	scriptCode = 'Cyrl';
	}
	break;
	}
	}
	// Increment length if we were able to assume a scriptCode.
	if (scriptCode != null) {
	length += 1;
	}
	// Update the base string to reflect assumed scriptCodes.
	originalString = languageCode;
	if (scriptCode != null) {
	originalString += '_$scriptCode';
	}
	if (countryCode != null) {
	originalString += '_$countryCode';
	}
	}

	return LocaleInfo(
	languageCode: languageCode,
	scriptCode: scriptCode,
	countryCode: countryCode,
	length: length,
	originalString: originalString,
	);
	}

	final String languageCode;
	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.

	String camelCase() {
	return originalString
	.split('_')
	.map<String>((String part) => part.substring(0, 1).toUpperCase() + part.substring(1).toLowerCase())
	.join();
	}

	@override
	bool operator ==(Object other) {
	return other is LocaleInfo
	&& other.originalString == originalString;
	}

	@override
	int get hashCode => originalString.hashCode;

	@override
	String toString() {
	return originalString;
	}

	@override
	int compareTo(LocaleInfo other) {
	return originalString.compareTo(other.originalString);
	}
	}

	// 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>>{};
	late List<String> lastHeading;
	for (final String line in section.split('\n')) {
	if (line == '') {
	continue;
	}
	if (line.startsWith(' ')) {
	lastHeading[lastHeading.length - 1] = '${lastHeading.last}${line.substring(1)}';
	continue;
	}
	final int colon = line.indexOf(':');
	if (colon <= 0) {
	throw 'not sure how to deal with "$line"';
	}
	final String name = line.substring(0, colon);
	final String value = line.substring(colon + 2);
	lastHeading = result.putIfAbsent(name, () => <String>[]);
	result[name]!.add(value);
	}
	return result;
	}

	final Map<String, String> _languages = <String, String>{};
	final Map<String, String> _regions = <String, String>{};
	final Map<String, String> _scripts = <String, String>{};
	const String kProvincePrefix = ', Province of ';
	const String kParentheticalPrefix = ' (';

	/// Prepares the data for the [describeLocale] method below.
	///
	/// The data is obtained from the official IANA registry.
	void precacheLanguageAndRegionTags() {
	final List<Map<String, List<String>>> sections =
	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;
	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(' ');
	if (description.startsWith('United ')) {
	description = 'the $description';
	}
	if (description.contains(kParentheticalPrefix)) {
	description = description.substring(0, description.indexOf(kParentheticalPrefix));
	}
	if (description.contains(kProvincePrefix)) {
	description = description.substring(0, description.indexOf(kProvincePrefix));
	}
	if (description.endsWith(' Republic')) {
	description = 'the $description';
	}
	switch (type) {
	case 'language':
	_languages[subtag] = description;
	break;
	case 'region':
	_regions[subtag] = description;
	break;
	case 'script':
	_scripts[subtag] = description;
	break;
	}
	}
	}
	}

	String describeLocale(String tag) {
	final List<String> subtags = tag.split('_');
	assert(subtags.isNotEmpty);
	assert(_languages.containsKey(subtags[0]));
	final String language = _languages[subtags[0]]!;
	String output = language;
	String? region;
	String? script;
	if (subtags.length == 2) {
	region = _regions[subtags[1]];
	script = _scripts[subtags[1]];
	assert(region != null \|\| script != null);
	} else if (subtags.length >= 3) {
	region = _regions[subtags[2]];
	script = _scripts[subtags[1]];
	assert(region != null && script != null);
	}
	if (region != null) {
	output += ', as used in $region';
	}
	if (script != null) {
	output += ', using the $script script';
	}
	return output;
	}

	/// Return the input string as a Dart-parsable string.
	///
	/// ```
	/// foo => 'foo'
	/// foo "bar" => 'foo "bar"'
	/// foo 'bar' => "foo 'bar'"
	/// foo 'bar' "baz" => '''foo 'bar' "baz"'''
	/// ```
	///
	/// This function is used by tools that take in a JSON-formatted file to
	/// generate Dart code. For this reason, characters with special meaning
	/// in JSON files are escaped. For example, the backspace character (\b)
	/// has to be properly escaped by this function so that the generated
	/// Dart code correctly represents this character:
	/// ```
	/// foo\bar => 'foo\\bar'
	/// foo\nbar => 'foo\\nbar'
	/// foo\\nbar => 'foo\\\\nbar'
	/// foo\\bar => 'foo\\\\bar'
	/// foo\ bar => 'foo\\ bar'
	/// foo$bar = 'foo\$bar'
	/// ```
	String generateString(String value) {
	const String backslash = '__BACKSLASH__';
	assert(
	!value.contains(backslash),
	'Input string cannot contain the sequence: '
	'"__BACKSLASH__", as it is used as part of '
	'backslash character processing.'
	);

	value = value
	// Replace backslashes with a placeholder for now to properly parse
	// other special characters.
	.replaceAll(r'\', backslash)
	.replaceAll(r'$', r'\$')
	.replaceAll("'", r"\'")
	.replaceAll('"', r'\"')
	.replaceAll('\n', r'\n')
	.replaceAll('\f', r'\f')
	.replaceAll('\t', r'\t')
	.replaceAll('\r', r'\r')
	.replaceAll('\b', r'\b')
	// Reintroduce escaped backslashes into generated Dart string.
	.replaceAll(backslash, r'\\');

	return "'$value'";
	}

	/// Typed configuration from the localizations config file.
	class LocalizationOptions {
	const LocalizationOptions({
	this.arbDirectory,
	this.templateArbFile,
	this.outputLocalizationsFile,
	this.untranslatedMessagesFile,
	this.header,
	this.outputClass,
	this.outputDirectory,
	this.preferredSupportedLocales,
	this.headerFile,
	this.deferredLoading,
	this.useSyntheticPackage = true,
	this.areResourceAttributesRequired = false,
	this.usesNullableGetter = true,
	}) : assert(useSyntheticPackage != null);

	/// The `--arb-dir` argument.
	///
	/// The directory where all input localization files should reside.
	final Uri? arbDirectory;

	/// The `--template-arb-file` argument.
	///
	/// This URI is relative to [arbDirectory].
	final Uri? templateArbFile;

	/// The `--output-localization-file` argument.
	///
	/// This URI is relative to [arbDirectory].
	final Uri? outputLocalizationsFile;

	/// The `--untranslated-messages-file` argument.
	///
	/// This URI is relative to [arbDirectory].
	final Uri? untranslatedMessagesFile;

	/// The `--header` argument.
	///
	/// The header to prepend to the generated Dart localizations.
	final String? header;

	/// The `--output-class` argument.
	final String? outputClass;

	/// The `--output-dir` argument.
	///
	/// The directory where all output localization files should be generated.
	final Uri? outputDirectory;

	/// The `--preferred-supported-locales` argument.
	final List<String>? preferredSupportedLocales;

	/// The `--header-file` argument.
	///
	/// A file containing the header to prepend to the generated
	/// Dart localizations.
	final Uri? headerFile;

	/// The `--use-deferred-loading` argument.
	///
	/// Whether to generate the Dart localization file with locales imported
	/// as deferred.
	final bool? deferredLoading;

	/// The `--synthetic-package` argument.
	///
	/// 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;

	/// The `nullable-getter` argument.
	///
	/// Whether or not the localizations class getter is nullable.
	final bool usesNullableGetter;
	}

	/// Parse the localizations configuration options from [file].
	///
	/// Throws [Exception] if any of the contents are invalid. Returns a
	/// [LocalizationOptions] with all fields as `null` if the config file exists
	/// but is empty.
	LocalizationOptions parseLocalizationsOptions({
	required File file,
	required Logger logger,
	}) {
	final String contents = file.readAsStringSync();
	if (contents.trim().isEmpty) {
	return const LocalizationOptions();
	}
	final YamlNode yamlNode = loadYamlNode(file.readAsStringSync());
	if (yamlNode is! YamlMap) {
	logger.printError('Expected ${file.path} to contain a map, instead was $yamlNode');
	throw Exception();
	}
	return LocalizationOptions(
	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,
	usesNullableGetter: _tryReadBool(yamlNode, 'nullable-getter', logger) ?? true,
	);
	}

	// 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];
	if (value == null) {
	return null;
	}
	if (value is! bool) {
	logger.printError('Expected "$key" to have a bool value, instead was "$value"');
	throw Exception();
	}
	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];
	if (value == null) {
	return null;
	}
	if (value is! String) {
	logger.printError('Expected "$key" to have a String value, instead was "$value"');
	throw Exception();
	}
	return value;
	}

	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);
	if (value == null) {
	return null;
	}
	final Uri? uri = Uri.tryParse(value);
	if (uri == null) {
	logger.printError('"$value" must be a relative file URI');
	}
	return uri;
	}