Add Locale.toLanguageTag() (#8421)

Adds `Locale.toLanguageTag()`, which returns a valid Unicode Locale Identifier using underscores as separator that can be reliably parsed.
flutter · Apr 8, 2019 · 78bd318 · 78bd318
1 parent efb3b00
commit 78bd318
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Showing 2 changed files with 29 additions and 8 deletions.
diff --git a/lib/ui/window.dart b/lib/ui/window.dart
@@ -374,21 +374,35 @@ class Locale {
   static Locale cachedLocale;
   static String cachedLocaleString;
 
+  /// Returns a string representing the locale.
+  ///
+  /// This identifier happens to be a valid Unicode Locale Identifier using
+  /// underscores as separator, however it is intended to be used for debugging
+  /// purposes only. For parseable results, use [toLanguageTag] instead.
   @override
-  String toString() {
+  String toString() => _toLanguageTag('_');
+
+  /// Returns a syntactically valid Unicode BCP47 Locale Identifier.
+  ///
+  /// Some examples of such identifiers: "en", "es-419", "hi-Deva-IN" and
+  /// "zh-Hans-CN". See http://www.unicode.org/reports/tr35/ for technical
+  /// details.
+  String toLanguageTag() => _toLanguageTag();
+
+  String _toLanguageTag([String separator = '-']) {
     if (!identical(cachedLocale, this)) {
       cachedLocale = this;
-      cachedLocaleString = _rawToString();
+      cachedLocaleString = _rawToString(separator);
     }
     return cachedLocaleString;
   }
 
-  String _rawToString() {
+  String _rawToString(String separator) {
     final StringBuffer out = StringBuffer(languageCode);
     if (scriptCode != null)
-      out.write('_$scriptCode');
+      out.write('$separator$scriptCode');
     if (_countryCode != null)
-      out.write('_$countryCode');
+      out.write('$separator$countryCode');
     return out.toString();
   }
 }

diff --git a/testing/dart/locale_test.dart b/testing/dart/locale_test.dart
@@ -9,13 +9,15 @@ import 'package:test/test.dart';
 void main() {
   test('Locale', () {
     const Null $null = null;
-    expect(const Locale('en').toString(), 'en');
+    expect(const Locale('en').toLanguageTag(), 'en');
     expect(const Locale('en'), const Locale('en', $null));
     expect(const Locale('en').hashCode, const Locale('en', $null).hashCode);
     expect(const Locale('en'), isNot(const Locale('en', '')));
     expect(const Locale('en').hashCode, isNot(const Locale('en', '').hashCode));
+    expect(const Locale('en', 'US').toLanguageTag(), 'en-US');
     expect(const Locale('en', 'US').toString(), 'en_US');
-    expect(const Locale('iw').toString(), 'he');
+    expect(const Locale('iw').toLanguageTag(), 'he');
+    expect(const Locale('iw', 'DD').toLanguageTag(), 'he-DE');
     expect(const Locale('iw', 'DD').toString(), 'he_DE');
     expect(const Locale('iw', 'DD'), const Locale('he', 'DE'));
   });
@@ -25,17 +27,22 @@ void main() {
     expect(const Locale.fromSubtags().scriptCode, null);
     expect(const Locale.fromSubtags().countryCode, null);
 
-    expect(const Locale.fromSubtags(languageCode: 'en').toString(), 'en');
+    expect(const Locale.fromSubtags(languageCode: 'en').toLanguageTag(), 'en');
     expect(const Locale.fromSubtags(languageCode: 'en').languageCode, 'en');
+    expect(const Locale.fromSubtags(scriptCode: 'Latn').toLanguageTag(), 'und-Latn');
     expect(const Locale.fromSubtags(scriptCode: 'Latn').toString(), 'und_Latn');
     expect(const Locale.fromSubtags(scriptCode: 'Latn').scriptCode, 'Latn');
+    expect(const Locale.fromSubtags(countryCode: 'US').toLanguageTag(), 'und-US');
     expect(const Locale.fromSubtags(countryCode: 'US').toString(), 'und_US');
     expect(const Locale.fromSubtags(countryCode: 'US').countryCode, 'US');
 
+    expect(const Locale.fromSubtags(languageCode: 'es', countryCode: '419').toLanguageTag(), 'es-419');
     expect(const Locale.fromSubtags(languageCode: 'es', countryCode: '419').toString(), 'es_419');
     expect(const Locale.fromSubtags(languageCode: 'es', countryCode: '419').languageCode, 'es');
+    expect(const Locale.fromSubtags(languageCode: 'es', countryCode: '419').scriptCode, null);
     expect(const Locale.fromSubtags(languageCode: 'es', countryCode: '419').countryCode, '419');
 
+    expect(const Locale.fromSubtags(languageCode: 'zh', scriptCode: 'Hans', countryCode: 'CN').toLanguageTag(), 'zh-Hans-CN');
     expect(const Locale.fromSubtags(languageCode: 'zh', scriptCode: 'Hans', countryCode: 'CN').toString(), 'zh_Hans_CN');
   });