l10n_mapper_generator 2.2.0

A dart package to generate localization-mapper to support parsing dynamic translation keys (as flutter-localizations package does not yet support this).

l10n_mapper_generator

A dart package to support parsing dynamic translation keys (as flutter-localizations package does not yet support this).

Note: Setup localization using flutter_localizations package before proceeding with this and also ensure localization setup is not a synthetic package.

Getting started

l10n_mapper_generator: >=2.0.0 deprecates the use of l10n_mapper_annotation as annotation is no longer required to work with >=2.0.0

Install dependencies

dependencies:
  flutter:
    sdk: flutter

  flutter_localizations:
    sdk: flutter

dev_dependencies:
  build_runner: ^2.3.3

  l10n_mapper_generator: <latest-version>

To run l10n_mapper_generator in terminal, you should activate/install it as a global dependency

dart pub global activate l10n_mapper_generator

Example usage

Note: parameters, are parsed as a list of positional arguments which should be in the same order as specified in the translation key-value pair.

  final applicationName = context.parseL10n('application_name'); // Localization mapper
  final depositTimeFrame = context.parseL10n('deposit_timeframe'); // Instant

  // parsing placeholder parameters
  final convertBeforeWithdraw = context.parseL10n('convert_before_withdraw', arguments: ['CAD', 'EUR']); // * For withdrawing your CAD you first need to convert it back to EUR

Mapper

This generates a app_localizations.g.dart file provided your project already setup localization. With generated app_localizations.dart, utility methods are generated for dynamic localization-keys access by the generator.

By default, this generates a app_localizations.g.dart file consisting of l10n, locale and parseL10n extension methods on bulild context and also a AppLocalizationsMapper class consisting of all key-value pairs defined in the generated app_localizations.dart localization file.

You can customize the behavior on what to generate by specifying some build configurations in your project's build.yaml file or stick with the default configs which generates all required extension methods. Below are all possible configuration options

# build.yaml

targets:
  $default:
    builders:
      l10n_mapper_generator:l10n_mapper_builder:
        enabled: true  # enables or disables the builder
        options:
          l10n: true # optional default - true
          locale: true # optional default - true
          parseL10n: true # optional default - true
          message: "Translation key not found!" # optional default - null
          classNames: "AppLocalizations,AppLocalizationsPushNotifications" # optional default - AppLocalizations

To generate app-localization mapper that can be parsed dynamic translation keys, you should simply

• run flutter gen-l10n to generate app_localizations.dart file with localization related files
• run flutter pub run build_runner build --delete-conflicting-outputs to generate app_localizations.g.dart file (if not already generated)

Available Options

• l10n: boolean-value with default as true - required to generate l10n extension method
• locale: boolean-value with default as true - required to generate locale extension method
• l10nParser: boolean-value with default as true - required to generate l10nParser extension method
• appLocalizations: location of your generated app_localizations.dart file after running flutter gen-l10n
• message: A fallback message to return when translation-key is not found. When this is provided, parseL10n extension method returns message when translation key is not found else it returns a nullable string type String?.
• classNames: A comma-separated list of class-names to generate mapper for. This is useful when you have multiple localization files generated by flutter gen-l10n and you want to generate mapper for all of them.

• run the following scripts in succession (after setting-up l10n_mapper.json configuration file)

# Generates flutter localization files and configs
flutter gen-l10n

# Generate required code (this should generate `app_localizations.g.dart` consisting of `AppLocalizationsExtension` and `AppLocalizationsMapper` classes)
flutter pub run build_runner build --delete-conflicting-outputs

Format (--format)

This generator flag indicates formatting translation-file keys to match dart naming convention for translations to generate dart translation related files. A simple usecase for this is utilizing the same translation files originally defined for other frameworks

Example

<!-- en-English.arb -->
<!-- this was originally defined with compatible naming convention for a typescript/javascript project -->

"test.send_your_USDT(TRON)_withdraw": "Send your USDT (TRC-20) withdrawal to:",
"@test.send_your_USDT(TRON)_withdraw": {
"type": "text"
},

Originally, the above example was defined for typescript/javascript support. Using --format flag formats these keys to support dart-naming convention which is compatible for dart to generate localization related files without errors when running flutter gen-l10n.

To format translation-files, you can simply

• setup l10n_mapper.json configuration file in your project`s root directory with the following options

// l10n_mapper.json

{
  "formatterOptions": {
    "prefix": "app", // file-name prefix to apply when creating translation-file after formatting
    "inputPath": "lib/localization/translations/remote", // directory containing translation-files that require formatting
    "outputPath": "lib/localization/translations/local", // directory where translation files will be create-in after formatting
    "translations": [
      {
        "locale": "ar", // locale of translation after formatting
        "input": "ar-Arabic.arb", // translation requiring formatting
        "output": "ar.arb" // translation name after formatting eg. app_ar.arb (appended prefix after formatting)
      },
      {
        "locale": "de",
        "input": "de-German.arb",
        "output": "de.arb"
      },
      {
        "locale": "en",
        "input": "en-English.arb",
        "output": "en.arb"
      }
    ],
    "keyPredicateMatch": { // contains all predicates to match and replace eg. `.` will be replace with `_` when found in a key
      "-": "_",
      ".": "_",
      "^": "_",
      "(": "_",
      ")": "_"
    }
  },
}

• run flutter gen-l10n to generate app_localizations.dart file with localization related files
• run flutter pub run build_runner build command to generate the formatted files and other generator files as well

NOTE: Given the above configuration setup of l10n_mapper.json, the generated translation file for the above example will be

<!-- app_en.arb -->
<!--
this is now compatible with dart naming convention with
- uppercase characters converted to lowercase
- all `.`, `(` and `)` converted to `_`
-->

"test_send_your_usdt_tron_withdraw": "Send your USDT (TRC-20) withdrawal to:",
"@test_send_your_usdt_tron_withdraw": {
"type": "text"
},

Note: For convenience and a cleaner reuseable approach, you can create a shell script (in the projects root directory) to collectively run the above scripts in succession.

You should setup l10n_mapper.json configuration file before running dart pub run l10n_mapper_generator command

./generate_localization.sh

#!/bin/bash

# format translation-files in `translations/remote` to dart compatible format
dart pub run l10n_mapper_generator --format

# generate localization-related files
flutter gen-l10n

# Generate required code (this should generate `app_localizations.g.dart` consisting of `AppLocalizationsExtension` and `AppLocalizationsMapper` classes)
flutter pub run build_runner build --delete-conflicting-outputs

To run this, you can simply run the following in your terminal (project root-directory)

• make ./generate_localization.sh executable by running chmod +x ./generate_localization.sh
• run script by running ./generate_localization.sh.

Note: You can parse the directory path to find l10n_mapper.json if it is not defined in the projects' root directory (default expected location) when running dart pub run l10n_mapper_generator command.

#  provide path to directory where `l10n_mapper.json` is defined
dart pub run l10n_mapper_generator --config=lib/config # directory contains `l10n_mapper.json` configuration file

Note: Providing formatter config with keyPredicateMatch values, ensures matched predicate are replaced with specified value in the config e.g {"^": "_"} means thats all ^ found in translation-keys will be replaced with _ (underscore) instead.

// before formatting
"test^send^your^usdt": "Send your USDT (TRC-20) withdrawal to:",

// after formatting
"test_send_your_usdt": "Send your USDT (TRC-20) withdrawal to:",

When a an empty value is defined for keyPredicateMatch like below

"keyPredicateMatch": {
"-": "",
".": "",
"^": "_",
"(": "_",
")": "_"
}

The translation-keys are formatted using camel-case where a key-predicate is matched for - and .. Given the previous example, the key will be formatted as below

// before formatting
"test^send.your-usdt": "Send your USDT (TRC-20) withdrawal to:",

// after formatting
"test_sendYourUsdt": "Send your USDT (TRC-20) withdrawal to:",

With this flexibility, one can decide to prefer camel or snake casing which are both compatible with dart method naming signature and suitable for dart generated translation objects.

Helper extensions

To access translations dynamically and parse placeholder parameters, a part file of app-localizations.dart is generated consisting of an access extension on build-context and a mapper.

// GENERATED CODE - DO NOT MODIFY BY HAND

// **************************************************************************
// L10nMapperGenerator
// **************************************************************************

import 'app_localizations.dart';
import 'package:flutter/widgets.dart';

extension AppLocalizationsExtension on BuildContext {
  AppLocalizations get _localizations => AppLocalizations.of(this)!;
  AppLocalizations get l10n => _localizations;
  Locale get locale => Localizations.localeOf(this);
  String parseL10n(String translationKey, {List<Object>? arguments}) {
    const mapper = AppLocalizationsMapper();
    final object = mapper.toLocalizationMap(this)[translationKey];
    if (object == null) return 'Cannot find translation-key!';
    if (object is String) return object;
    assert(arguments != null, 'Arguments should not be null!');
    assert(arguments!.isNotEmpty, 'Arguments should not be empty!');
    return Function.apply(object, arguments);
  }
}

class AppLocalizationsMapper {
  const AppLocalizationsMapper();
  Map<String, dynamic> toLocalizationMap(BuildContext context) {
    final localizations = AppLocalizations.of(context)!;
    return {
      'localeName': localizations.localeName,
      'application_name': localizations.application_name,
      'deposit_timeframe': localizations.deposit_timeframe,
      'balance_reverted': (currency) => localizations.balance_reverted(currency),
      'convert_before_withdraw': (convertFrom, convertTo) => localizations.convert_before_withdraw(convertFrom, convertTo),
      'convert_before_withdraw_again': (convertFrom, convertTo) => localizations.convert_before_withdraw_again(convertFrom, convertTo),
    };
  }
}

Resources

Here is a proposal this package is aimed to resolve

• [Proposal] Access l18n Translations with Dynamic Keys #105672

Note: Your PRs regarding this is highly encouraged and welcome

For more information, checkout the example project.