Function highlight

packages/react/src/lib/shiki.ts:218–241

(options, callback)

    getThemes: () => [DEFAULT_LIGHT_THEME as ThemeInput, DEFAULT_DARK_THEME as ThemeInput],
    supportsLanguage: (language: string) => isSupportedLang(language),
    highlight(options, callback) {
      const resolved = resolveLang(options.language);
      const lang = resolved ?? "json";
      // Dual-theme tokens (light-dark() colors): correct in both color
      // schemes, so the cache never holds the wrong palette and a mid-stream
      // scheme flip needs no re-render.
      const key = `${lang}:${options.code.length}:${options.code.slice(0, 128)}`;

      const cached = tokensCache.get(key);
      if (cached) return cached;

      const isReady = ensureLang(lang, () => {
        // Language just loaded — highlight and notify via callback
        const result = highlighter.codeToTokens(options.code, { lang, ...dualThemeOptions() });
        tokensCache.set(key, result);
        callback?.(result);
      });

      if (!isReady) return null;

      const result = highlighter.codeToTokens(options.code, { lang, ...dualThemeOptions() });
      tokensCache.set(key, result);
      return result;
    },
  };
}