Improve error handling in `handle` about slacker HOT 1 CLOSED

It's not entirely trivial defining in which way this should concretely manifest. One approach could be the following:

(testing "One failing handler should not kill other handlers"
  (let [promises (into [] (repeatedly 100 promise))]
    (handle :danger (fn [a])) ; Throws clojure.lang.ArityException
    (dotimes [i 100]
      (handle :danger #(deliver (get promises i) true)))
    (emit! :danger)
    (is (every? true? (map deref promises)))))

Why 100? The test is about an exception not ruining any pending and future handlers, and with 100 extra handlers it is unlikely that the handler throwing an ArityException runs as the very last. This leaves the pertinent question of how to notice errors in your handlers at all. I guess this necessitates some sort of logging, which was planned anyway.

from slacker.