flutter_localizations does not support all installer languages

[jpnurmi]

There are a few languages (Cymraeg, Esperanto, ...) that cause Flutter to throw an exception because MaterialLocalizations doesn't support all languages that the installer's AppLocalizations includes:

[oSoMoN]

For those we'll need to do the same as for Occitan, i.e. implement a suitable MaterialLocalization and a LocalizationsDelegate (see https://github.com/canonical/ubuntu-desktop-installer/blob/main/packages/ubuntu_wizard/lib/l10n.dart#L119).

[Mejans]

Many thanks @oSoMoN for this by the way ;)

[jpnurmi]

In addition to oc, MaterialLocalizations is missing for:

• [x] cy (Welsh;Cymraeg)
• [x] eo (Esperanto;Esperanto)
• [x] ga (Irish;Gaeilge)
• [x] ku (Kurdish;Kurdî)
• [x] nn_NO (Norwegian Nynorsk;Norsk nynorsk)
• [x] se_NO (Northern Sami;Sámegillii)
• [x] tg (Tajik;Тоҷикӣ)
• [x] ug (Uyghur;ئۇيغۇرچە)
• [x] bo (Tibetan;བོད་ཡིག)
• [x] dz (Dzongkha;རྫོང་ཁ)

[jpnurmi]

Out of these, the intl package has built-in support for cy and ga:

import 'package:intl/date_symbol_data_local.dart';
import 'package:intl/intl.dart';

Future<void> main(List<String> arguments) async {
  await initializeDateFormatting();
  print('cy: ${DateFormat.localeExists("cy")}'); // true
  print('eo: ${DateFormat.localeExists("eo")}'); // false
  print('ga: ${DateFormat.localeExists("ga")}'); // true
  print('ku: ${DateFormat.localeExists("ku")}'); // false
  print('nn_NO: ${DateFormat.localeExists("nn_NO")}'); // false
  print('se_NO: ${DateFormat.localeExists("se_NO")}'); // false
  print('tg: ${DateFormat.localeExists("tg")}'); // false
  print('ug: ${DateFormat.localeExists("ug")}'); // false
  print('bo: ${DateFormat.localeExists("bo")}'); // false
  print('dz: ${DateFormat.localeExists("dz")}'); // false
}

[jpnurmi]

At first, it looks somewhat straightforward when you start reading the Adding support for a new language section in the Flutter docs. Then, you notice that nnLocaleDatePatterns and nnDateSymbols are just stubs. It starts getting more interesting when looking at the complete add_language example.

Relevant issues:

• https://github.com/flutter/flutter/issues/66553
• https://github.com/dart-lang/i18n/issues/88

It boils down to missing locale data in the intl package. Unfortunately, the tools, that could be used for generating the missing data from CLDR, are not public.

• intl/lib/date_symbol_data_local.dart:

  /// DO NOT EDIT. This file is autogenerated by script. See /// 'http://go/generate_datetime_constants.py' using the --for_dart /// flag. /// File generated from CLDR ver. 35.1

• lib/date_time_patterns.dart

  /// DO NOT EDIT. This file is autogenerated from ICU data. See /// 'http://go/generate_datetime_pattern_dart.cc' (Google internal) /// File generated from CLDR ver. 35.1

[jpnurmi]

For reference

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

abstract class MaterialLocalizations {
  String get cancelButtonLabel;
  static MaterialLocalizations of(BuildContext context)
}

class _MaterialLocalizationsDelegate extends LocalizationsDelegate<MaterialLocalizations>{
  bool isSupported(Locale locale) => locale.languageCode == 'en';
  Future<MaterialLocalizations> load(Locale locale) => DefaultMaterialLocalizations.load(locale);
}

class DefaultMaterialLocalizations implements MaterialLocalizations {
  String get cancelButtonLabel => 'CANCEL';
  static Future<MaterialLocalizations> load(Locale locale) {
    return SynchronousFuture<MaterialLocalizations>(const DefaultMaterialLocalizations());
  }
  static const LocalizationsDelegate<MaterialLocalizations> delegate = _MaterialLocalizationsDelegate();
}

flutter_localizations/lib/src/material_localizations.dart:

abstract class GlobalMaterialLocalizations implements MaterialLocalizations {
  static const LocalizationsDelegate<MaterialLocalizations> delegate = _MaterialLocalizationsDelegate();
  static const List<LocalizationsDelegate<dynamic>> delegates = <LocalizationsDelegate<dynamic>>[
    GlobalCupertinoLocalizations.delegate,
    GlobalMaterialLocalizations.delegate,
    GlobalWidgetsLocalizations.delegate,
  ];
}

class _MaterialLocalizationsDelegate extends LocalizationsDelegate<MaterialLocalizations> {
  bool isSupported(Locale locale) => kMaterialSupportedLanguages.contains(locale.languageCode);
  Future<MaterialLocalizations> load(Locale locale) {
    final String localeName = intl.Intl.canonicalizedLocale(locale.toString());
    return SynchronousFuture<MaterialLocalizations>(...);
  }
}

flutter_localizations/lib/src/l10n/generated_material_localizations.dart:

class MaterialLocalizationFi extends GlobalMaterialLocalizations {
  String get cancelButtonLabel => 'PERUUTA';
}

P.S. Notice two different _MaterialLocalizationsDelegate classes.

[jpnurmi]

Solved by dart-lang/intl#506

[jpnurmi]

The issue is back. We need the same delegates for Cupertino due to Material's dependency on Cupertino through the various "adaptive" widgets.

[Mejans]

Many thanks for taking care of our languages!

[jpnurmi]

np :) fixed again by #1392