I've seen a lot of people asking us to review their DBAL, or MVC framework, or templating system, etc. While I totally support these people's efforts as a good way to learn, I think answering such involved questions could be a huge drain on the community.
On that note, would an acceptable answer be "see vendor X's code", or should we try to answer all questions, regardless of how novel they are?
Reinventing the wheel can actually be a useful exercise. But letting someone reinvent the wheel when they don't know they are doing it is a problem.
Pointing out that a ready-made solutions exists is helpful part of an answer. But you should still provide a review of the code itself. If you don't want to can't, you should probably just leave a comment pointing to wheel's website. Just posting an answer saying to use that wheel isn't really a code review.
There's also reinventing-the-wheel that can be used to signal to others that the asker knows that they're asking for help reimplementing something.
