I think an index of all documents (including the contained text etc) should be a standardized component / API of every modern OS. Windows has had one since Vista (no idea about the API though), Spotlight has been a part of OS X for two decades, and there are various solutions for Linux & friends; however as far as I can tell there's no cross-platform wrapper that would make any or all of these easy to integrate with e.g. your IDE. That would be cool to have.