sealed_language_subtags

A pure Dart package that provides the complete IANA Language Subtag Registry (BCP 47 / RFC 5646) as compile-time constant, tree-shakable, sealed classes.

The data is regenerated automatically from the canonical IANA source, so it is always current.

Features

• Every registry record as a const instance: languages, extended languages, scripts, regions, variants, grandfathered and redundant tags.
• A sealed `LanguageSubtag` hierarchy enabling exhaustive switch matching over the registry Type.
• Static entry points on LanguageSubtag: list, per-type lists and …Maps, from…/maybeFrom… lookups (accepting any Object code and an optional subset), maybeFromValue, is… type helpers, copyWith, a verbose toString({bool short}), and toMap/toJson/fromJson — mirroring the sealed_regions/sealed_languages API.
• Case-insensitive lookups per type (BCP 47 comparison rules).
• No third-party dependencies.

Common fields on every record: subtag, descriptions, added, deprecated, preferredValue, comments.

Usage

import 'package:sealed_language_subtags/sealed_language_subtags.dart';

void main() {
  // Case-insensitive lookup (nullable and throwing variants).
  final english = LanguageSubtag.maybeFromLanguage('en');
  print(english?.description); // English
  print(english?.suppressScript); // Latn

  // Exhaustive pattern matching over the sealed hierarchy.
  final LanguageSubtag subtag = LanguageSubtag.fromScript('Latn');
  final label = switch (subtag) {
    Language(:final description) => 'Language: $description',
    ExtendedLanguage(:final description) => 'Ext. language: $description',
    Script(:final description) => 'Script: $description',
    Region(:final description) => 'Region: $description',
    Variant(:final description) => 'Variant: $description',
    Grandfathered(:final description) => 'Grandfathered: $description',
    Redundant(:final description) => 'Redundant: $description',
  };
  print(label); // Script: Latin

  // All records, and per-type lists.
  print(LanguageSubtag.list.length);
  print(LanguageSubtag.languages.length);
}

Versioning

This package uses a hybrid SemVer/CalVer scheme: 1.<yyyy><mm>.<d>, derived from the registry's File-Date (the date IANA published the data). For example, the subtag registry dated 2026-08-08 is published as 1.202608.8. The major version stays at 1 while the API is stable, and the day (patch) has no leading zero.

Data source & license

The package code is © 2026 TigerC10, released under the MIT license (see LICENSE). The embedded data is sourced from the public IANA registry and remains subject to its terms.