i18n plugin

Folio's i18n foundation plugin validates and normalizes a page's locale metadata. It reads a locale from frontmatter and applies the configured default when a page does not declare one.

import { createI18nPlugin } from "@/plugins/i18n";

export default {
  plugins: [
    createI18nPlugin({
      defaultLocale: "en",
      locales: ["en", "ka"],
      translations: { directory: "locales" },
    }),
  ],
};

Declare an explicit locale when a page differs from the default:

---
title: საწყისი გვერდი
locale: ka
---

For real localized routes, store content in locale directories:

docs/
├── guide.mdx        # default locale, served at /guide
└── ka/
    └── guide.mdx    # served at /ka/guide

An explicitly prefixed default locale is also normalized:

docs/en/guide.mdx    # served at /guide

Every generated route points to its actual MDX filePath, so the plugin does not duplicate untranslated source content.

The plugin preserves slug and url, and writes the normalized locale back to the configured frontmatter key. An unsupported locale fails the page transformation with plugin metadata, so invalid translations cannot silently enter the build.

The plugin also loads global interface translations from JSON files under the configured directory:

locales/
├── en.json
└── ka.json

The default theme renders the language switcher in the navbar. It changes the site interface and navigates to the matching content page when that page exists. If the current page has no translation for the selected locale, that locale is disabled for the current page and the interface remains in the page's available locale. The locale segment is hidden from sidebar categories and breadcrumbs.

Unknown translation keys fail configuration loading. Missing keys and missing locale files fall back to the configured default locale.