scratch.clj

(def ^{:dynamic true} *handler* nil)

(defn error-point [fun]
  (let [[result exception] (binding [*handler* *handler*]
                             (try
                               [(fun) nil]
                               (catch Throwable t
                                 (if *handler*
                                   [nil (partial *handler* t)]
                                   (throw t)))))]
    (if exception
      (recur exception)
      result)))

(defn handle-errors [fun handler]
  (let [former-handler *handler*]
    (set! *handler* (fn [x]
                      (set! *handler* former-handler)
                      (handler x)))
    (let [x (fun)]
      (set! *handler* former-handler)
      x)))

(defmacro with-errors [& body]
  `(error-point (fn [] ~@body)))

(defmacro with-errror-continue [fun & body]
  `(handle-errors (fn [] ~@body) ~fun))

(defn set-error-continue! [handler]
  (let [former-handler *handler*]
    (set! *handler* (fn [x]
                      (set! *handler* former-handler)
                      (handler x)))))

(comment

  (with-errors
    (with-errror-continue (fn [_] (println "you have an error"))
      (+ 1 \a)))

  (with-errors
    (set-error-continue! (fn [_] (println "ERROR!")))
    (+ 1 \a))

  )