Internationalisation for Metanorma rendering.

isodoc-i18n is the shared i18n/l10n base layer used across the metanorma flavours. It provides:

• YAML-driven locale labels (IsoDoc::I18n#labels, populate) — per-language label sets loaded from i18n YAML, with cross-file references and Liquid template interpolation.

• CLDR-backed l10n of punctuation and spacing (#l10n) — CJK contextual half-width/full-width punctuation, French spacing rules, bidi wrapping for RTL scripts.

• Grammatical inflection and ordinals (#inflect, #inflect_ordinal) — number/case/gender/person inflection driven by per-language YAML inflection tables, plus CLDR OrdinalRules and SpelloutRules formatting.

• Liquid filter integration (IsoDoc::I18n::Liquid) — inflect, ordinal_num, ordinal_word, etc. registered globally on Liquid::Environment.default for use in metanorma templates.

• Boolean conjunction list rendering (#boolean_conj) — locale-correct "A, B, and C"-style joins.

• Extended date formatting (IsoDoc::I18n#date, IsoDoc::ExtendedDateFormatter) — see below.

Extended date formatting

isodoc-i18n ships an extended strftime-style date formatter, IsoDoc::ExtendedDateFormatter, that adds POSIX-flavoured era and alternative-numbering surfaces (Japanese era years, kanji spell-out, Han digits, Roman months) on top of Ruby’s Date#strftime. It is the engine behind IsoDoc::I18n#date and metanorma’s <date value="…" format="…"/> element, and can also be used standalone:

require "isodoc-i18n"

f = IsoDoc::ExtendedDateFormatter.new(lang: "ja", script: "Jpan")
f.format("2024-09-30", "%EY年%-m月%-d日")        # => "令和6年9月30日"

g = IsoDoc::ExtendedDateFormatter.new(lang: "en", script: "Latn")
g.format("2024-09-30", "%-d.%Om{roman}.%Y")      # => "30.IX.2024"

Full token reference, calendar dispatch rules, and a comparison with twitter_cldr, japanese_calendar, ffi-icu, and other adjacent tooling: docs/extended-date-format.adoc.