Function resolveLanguage

packages/rehype-shiki/src/highlighter.mjs:64–75

   * @returns {string}
   */
  const resolveLanguage = languageId => {
    const normalized = languageId?.toLowerCase();

    if (
      normalized &&
      (isSpecialLang(normalized) || loadedLanguages.has(normalized))
    ) {
      return languageId;
    }

    return FALLBACK_LANGUAGE;
  };

  /**
   * Highlights code and returns the inner HTML inside the <code> tag