Question

If I use Slingshot’s try+ and catch, it’s easy to write a selector to match on the contents of a map:

(defn dosomething (throw+ {:some :data}))
(try+ (dosomething)
    (catch [:some :data] ;; recover))

However, if I want to use ex-info, that catch selector doesn’t match the ExceptionInfo‘s data:

(defn dosomething (throw (ex-info "A message" {:some :data})))

Obviously I can catch an ExceptionInfo or write a custom predicate to match the data, I was just wondering if I was missing something about Slingshot or ex-info, as I’d been led to believe they worked together more smoothly than this.

Answer 1

I’m not really sure why you want to throw an ExceptionInfo, my understanding is it’s just a carrier for arbitrary data that you can just throw normally with throw+.

(throw+ {:some :data :msg "A message"})

Or if the point is that you don’t want to use throw+, then I don’t think there is a totally straightforward way to catch it. You’d have to do something like

(catch (-> % ex-data :some (= :data)) myerr (foo myerr))

I don’t know what the use case is for wanting to use try+ but not throw+.