Add locale-sensitive casing

pkgs/intl4x/lib/case_mapping.dart

@@ -0,0 +1,15 @@
+// Copyright (c) 2023, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'intl4x.dart';
+
+export 'intl4x.dart';
+export 'src/case_mapping/case_mapping.dart';
+
+extension CaseMappingWithIntl4X on String {
+  String toLocaleLowerCase(Locale locale) =>
+      Intl(locale: locale).caseMapping.toLowerCase(this);
+  String toLocaleUpperCase(Locale locale) =>
+      Intl(locale: locale).caseMapping.toLowerCase(this);
+}

pkgs/intl4x/lib/intl4x.dart

@@ -2,9 +2,11 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
+import 'case_mapping.dart';
 import 'collation.dart';
 import 'display_names.dart';
 import 'number_format.dart';
+import 'src/case_mapping/case_mapping_impl.dart';
 import 'src/collation/collation_impl.dart';
 import 'src/data.dart';
 import 'src/datetime_format/datetime_format.dart';
@@ -82,6 +84,9 @@ class Intl {
             localeMatcher, ecmaPolicy),
       );
 
+  CaseMapping get caseMapping => CaseMapping(
+      CaseMappingImpl.build(locale, data, localeMatcher, ecmaPolicy));
+
   /// Construct an [Intl] instance providing the current [locale] and the
   /// [ecmaPolicy] defining which locales should fall back to the browser
   /// provided functions.

pkgs/intl4x/lib/src/case_mapping/case_mapping.dart

@@ -0,0 +1,28 @@
+// Copyright (c) 2023, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import '../test_checker.dart';
+import 'case_mapping_impl.dart';
+
+class CaseMapping {
+  final CaseMappingImpl _caseMappingImpl;
+
+  const CaseMapping(this._caseMappingImpl);
+
+  String toLowerCase(String input) {
+    if (isInTest) {
+      return input;
+    } else {
+      return _caseMappingImpl.toLowerCase(input);
+    }
+  }
+
+  String toUpperCase(String input) {
+    if (isInTest) {
+      return input;
+    } else {
+      return _caseMappingImpl.toUpperCase(input);
+    }
+  }
+}

pkgs/intl4x/lib/src/case_mapping/case_mapping_4x.dart

@@ -0,0 +1,32 @@
+// Copyright (c) 2023, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import '../bindings/lib.g.dart' as icu;
+import '../data.dart';
+import '../data_4x.dart';
+import '../locale/locale.dart';
+import '../locale/locale_4x.dart';
+import 'case_mapping_impl.dart';
+
+CaseMappingImpl getCaseMapping4X(
+  Locale locale,
+  Data data,
+  Null _,
+) =>
+    CaseMapping4X(locale, data);
+
+class CaseMapping4X extends CaseMappingImpl {
+  final icu.CaseMapper _caseMapper;
+
+  CaseMapping4X(super.locale, Data data)
+      : _caseMapper = icu.CaseMapper(data.to4X());
+
+  @override
+  String toLowerCase(String input) =>
+      _caseMapper.lowercase(input, locale.to4X());
+
+  @override
+  String toUpperCase(String input) =>
+      _caseMapper.uppercase(input, locale.to4X());
+}

pkgs/intl4x/lib/src/case_mapping/case_mapping_ecma.dart

@@ -0,0 +1,39 @@
+// Copyright (c) 2023, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'dart:js_interop';
+
+import '../locale/locale.dart';
+import '../options.dart';
+import 'case_mapping_impl.dart';
+
+CaseMappingImpl? getCaseMappingECMA(
+  Locale locale,
+  Null __,
+  LocaleMatcher _,
+) =>
+    _CaseMappingECMA.tryToBuild(locale);
+
+extension on JSString {
+  @JS('String.toLocaleUpperCase')
+  external String toLocaleUpperCase(String locale);
+  @JS('String.toLocaleLowerCase')
+  external String toLocaleLowerCase(String locale);
+}
+
+class _CaseMappingECMA extends CaseMappingImpl {
+  _CaseMappingECMA(super.locale);
+
+  static CaseMappingImpl? tryToBuild(
+    Locale locale,
+  ) =>
+      _CaseMappingECMA(locale);
+  @override
+  String toUpperCase(String input) =>
+      input.toJS.toLocaleUpperCase(locale.toLanguageTag());
+
+  @override
+  String toLowerCase(String input) =>
+      input.toJS.toLocaleLowerCase(locale.toLanguageTag());
+}

pkgs/intl4x/lib/src/case_mapping/case_mapping_impl.dart

@@ -0,0 +1,40 @@
+// Copyright (c) 2023, the Dart project authors. Please see the AUTHORS file
+// for details. 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' show ResourceIdentifier;
+
+import '../../ecma_policy.dart';
+import '../data.dart';
+import '../ecma/ecma_policy.dart';
+import '../locale/locale.dart';
+import '../options.dart';
+import '../utils.dart';
+import 'case_mapping_stub.dart' if (dart.library.js) 'case_mapping_ecma.dart';
+import 'case_mapping_stub_4x.dart' if (dart.library.io) 'case_mapping_4x.dart';
+
+abstract class CaseMappingImpl {
+  final Locale locale;
+
+  CaseMappingImpl(this.locale);
+
+  String toLowerCase(String input);
+  String toUpperCase(String input);
+
+  @ResourceIdentifier('CaseMapping')
+  static CaseMappingImpl build(
+    Locale locales,
+    Data data,
+    LocaleMatcher localeMatcher,
+    EcmaPolicy ecmaPolicy,
+  ) =>
+      buildFormatter(
+        locales,
+        data,
+        null,
+        localeMatcher,
+        ecmaPolicy,
+        getCaseMappingECMA,
+        getCaseMapping4X,
+      );
+}

pkgs/intl4x/lib/src/case_mapping/case_mapping_stub.dart

@@ -0,0 +1,14 @@
+// Copyright (c) 2023, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import '../locale/locale.dart';
+import '../options.dart';
+import 'case_mapping_impl.dart';
+
+CaseMappingImpl? getCaseMappingECMA(
+  Locale locale,
+  Null _,
+  LocaleMatcher __,
+) =>
+    throw UnimplementedError('Cannot use ECMA outside of web environments.');

pkgs/intl4x/lib/src/case_mapping/case_mapping_stub_4x.dart

@@ -0,0 +1,14 @@
+// Copyright (c) 2023, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import '../data.dart';
+import '../locale/locale.dart';
+import 'case_mapping_impl.dart';
+
+CaseMappingImpl getCaseMapping4X(
+  Locale locale,
+  Data data,
+  Null _,
+) =>
+    throw UnimplementedError('Cannot use ICU4X in web environments.');

pkgs/intl4x/test/ecma/case_mapping_test.dart

@@ -0,0 +1,28 @@
+// Copyright (c) 2023, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+@TestOn('browser')
+library;
+
+import 'package:intl4x/case_mapping.dart';
+import 'package:test/test.dart';
+
+import '../utils.dart';
+
+void main() {
+  testWithFormatting('test name', () {
+    const enUS = const Locale(language: 'en', region: 'US');
+    expect('İstanbul'.toLocaleLowerCase(enUS), 'i̇stanbul');
+    expect('ALPHABET'.toLocaleLowerCase(enUS), 'alphabet');
+
+    expect('\u0130'.toLocaleLowerCase(const Locale(language: 'tr')), 'i');
+    expect('\u0130'.toLocaleLowerCase(enUS), isNot('i'));
+
+    final locales = ['tr', 'TR', 'tr-TR', 'tr-u-co-search', 'tr-x-turkish']
+        .map(Locale.parse);
+    for (final locale in locales) {
+      expect('\u0130'.toLocaleLowerCase(locale), 'i');
+    }
+  });
+}