Simplest way to post-process the result of a jQuery ajax request?

Question

Suppose I have a function fancyParse intended to take the response returned by the server and turn it into something else. This function throws if the response makes no sense whatsoever, or if it has a special "internal error" flag set.

I'd like to chain this function into a $.post call to get a new Deferred. This new deferred would fail if the request fails, or if fancyParse throws. It would succeed if the request succeeds and fancyParse succeeds, and, importantly, will pass the result of fancyParse to its success callbacks.

The perfect solution would look something like this:

$.post('/url', etc).postprocess(fancyParse)
    .done(my_done_handler)
    .fail(my_fail_handler);

Is something like this already available, or do I need to write such a postprocess myself?