inline_l10n

An authoring tool for Flutter's official gen-l10n localization workflow. Keep English ARB source text next to the typed AppLocalizations key that uses it.

inline_l10n is not a standalone localization framework. It depends on Flutter's flutter_localizations, intl, ARB files, and flutter gen-l10n for runtime localization and generated AppLocalizations accessors.

Flutter's gen-l10n normally generates typed localization accessors from ARB files. inline_l10n reverses the authoring flow: write English source text at its use site, generate app_en.arb, then let Flutter generate the accessors.

Text(l10n.settings.inline('Settings'))

At runtime, inline() returns the localized value from l10n.settings. Its English argument is used only by the generator.

What it does

  • Extracts .inline(...) calls from Dart source with the Dart analyzer AST.
  • Writes the English ARB file specified by l10n.yaml from the extracted strings.
  • Adds descriptions pointing to the defining source file.
  • Keeps every non-English ARB file aligned with the generated English keys.
  • Runs flutter gen-l10n after updating the ARB files.
  • Fails when the same localization key has conflicting English source text.

This package only changes how you author Flutter localization entries. Flutter still loads translations and formats messages at runtime. It does not translate strings.

Prerequisites

Set up Flutter's official localization system first. Your app needs flutter_localizations, intl, and localization generation enabled:

# pubspec.yaml
dependencies:
  flutter_localizations:
    sdk: flutter
  intl: any
  inline_l10n: ^0.1.0

flutter:
  generate: true

The generator reads the ARB directory and template filename from l10n.yaml:

# l10n.yaml
arb-dir: lib/resources/l10n
template-arb-file: app_en.arb

For example, a compatible l10n.yaml can be:

arb-dir: lib/resources/l10n
template-arb-file: app_en.arb
output-localization-file: app_localizations.dart
output-class: AppLocalizations
nullable-getter: false

Register the generated AppLocalizations delegates in your MaterialApp as described by Flutter's localization documentation.

Install

Run:

flutter pub get

inline_l10n is a regular dependency because its String.inline extension is compiled into your app.

Usage

Import the runtime marker where localized text is used:

import 'package:inline_l10n/inline_l10n.dart';

Write the English source text alongside a Flutter-generated AppLocalizations key:

final l10n = AppLocalizations.of(context);

Text(l10n.settings.inline('Settings'));

For arguments, use ICU placeholders in the English source and supply ARB placeholder metadata:

Text(
  l10n.greeting(name).inline(
    'Hello {name}',
    placeholders: {
      'name': {'type': 'String'},
    },
  ),
);

Run the generator from the Flutter app root:

dart run inline_l10n:gen_l10n

It creates or replaces app_en.arb, removes obsolete keys from every other app_*.arb file, and invokes flutter gen-l10n. Commit the generated ARB and Flutter localization output after reviewing the changes.

Recognized markers

The generator recognizes these forms:

l10n.key.inline('English text');
l10n.key(argument).inline('English {argument}');
AppLocalizations.of(context).key.inline('English text');

For local variables, the localization object must be named l10n. The source argument must be a string literal or adjacent string literals. String interpolation is not extracted; use ICU placeholders instead.

Important behavior

app_en.arb is the generated source of truth and is overwritten on each run. Other locale files retain only keys that still exist in app_en.arb; missing translations are not created. Keep ARB files under version control and review generator output before committing.

License

This project is licensed under the MIT License.

Libraries

inline_l10n