BCP-47

BCP-47 related types with parsing, formatting, canonicalization and format validation.

Features

The following types are implemented :

• RFC 5646 Language-Tag (langtag, grandfathered, privateuse),
• RFC 4647 Basic and Extended Language Range.

What it implements :

• Parsing and formatting (with letter case normalisation),
• Validation of well-formed Language-Tag / Language Range,
• Canonicalization of Language-Tag with IANA Language Subtag Registry,
• Basic and Extended filtering (cf. RFC 4647 section 3.3)
• Support for alternative subtags separator (like the underscore in CLDR data).

What it does NOT implement:

• Validation of Language-Tag subtags against IANA registry data (except for grandfathered tags).

Usage

Language-Tag

If you're unsure what type of Language-Tag you're parsing, use Bcp47LanguageTag.parse :

const strings = [
  'en',
  'i-unknown',
  'x-private',
];

for (final string in strings) {
    const languageTag = Bcp47LanguageTag.parse(string);

    // print primary and other subtags separately (RFC-3066 format)
    print(languageTag.primarySubtag);
    print(languageTag.otherSubtags);
    
    // print all the subtags
    print(languageTag.subtags);

    if (languageTag is Bcp47LangTag) {
        print(langTag.language);
        print(langTag.extlangs);
        print(langTag.script);
        print(langTag.region);
        print(langTag.extensions);
        print(langTag.privateUse);
    } else if (languageTag is Bcp47GrandfatheredTag) {
        print(languageTag.irregular);
    } else if (languageTag is Bcp47PrivateUseTag) {
        print(languageTag.singleton);
    }

    // print a case-normalized version of the tag
    print(languageTag.format(caseNormalized: true));
}

else you can use directly the correct type :

const langTagString = 'en-US';

const langTag = Bcp47LangTag.parse(langTagString);

Basic Language Range

final range = Bcp47BasicLanguageRange.parse('en');

final enUs = Bcp47LanguageTag.parse('en-US');
final frFr = Bcp47LanguageTag.parse('fr-FR');

// true
print(range.match(enUs));

// false
print(range.match(frFr));

Extended Language Range

final range = Bcp47ExtendedLanguageRange.parse('en-*-US');

final enUs = Bcp47LanguageTag.parse('en-US');
final enLatnUs = Bcp47LanguageTag.parse('en-Latn-US');
final enLatnCa = Bcp47LanguageTag.parse('en-Latn-CA');

// true
print(range.match(enUs));

// true
print(range.match(enLatnUs));

// false
print(range.match(enLatnCa));