On Wednesday, April 13, 2016 at 4:17:41 PM UTC-4, johnbclements wrote:
> Unless I’m misreading docs and source code, there’s currently no handin
> utility function that allows checking of the exception message.
>
> I propose adding !test/exn/msg, that accepts a regexp in addition to its
> other argument, and succeeds only if the message returned in the exception
> matches the given regexp. Essentially, just like rackunit’s `check-exn`,
> except that no thunk is required on the `actual` arg.
>
> I’d be happy to submit a pull request for this, if you folks think it makes
> sense. (Also, I’m open to suggestions on the ordering of the arguments.)
>
> Thoughts?
Unless I'm mistaken, or not reading you correctly, `with-handlers` takes
predicate - handler pairs... and that predicate can be pretty much anything you
want it to be. All's it needs to do is accept an exception as an argument and
return #t when you want it to.
So, would something like this work for your purposes?
(with-handlers ([(compose (curry regexp-match? #rx"some error message
substring, eh?")
exn-message)
(lambda (exn) (some-exn-handler-eh exn))])
(call-some-brittle-code))
What you propose is a pretty neat idea, though, but I can mash such a predicate
together with trivial uses of compose, curry, conjoin, and disjoin. If I were
to need to do something like that, I'd just do the composition, since it'll be
more familiar with me and it fits in better with the language's idioms.
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