serialize_exceptions.clj

(defn serialize-exception [e]
  {:message (.getMessage e)
   :ex-data (ex-data e)
   :stack-trace (map bean (.getStackTrace e))
   :cause (if-let [cause (.getCause e)]
            (serialize-exception cause))})

(defn ->StackTraceElement [{:keys [className methodName fileName lineNumber]}]
  (StackTraceElement. className methodName fileName lineNumber))

(defn deserialize-exception
  "Returns mocked Exception from serialized data.

   Only overrides getStackTrace, which is used at least by clojure.stacktrace/print-stack-trace
   and Boot to print the stacktrace. Some other stuff could call directly to
   printStackTrace."
  [{:keys [message ex-data stack-trace cause]}]
  (let [cause (if cause (deserialize-exception cause))
        stack-trace (into-array StackTraceElement (map ->StackTraceElement stack-trace))]
    (if ex-data
      (proxy [ExceptionInfo] [message ex-data cause]
        (getStackTrace []
          stack-trace))
      (proxy [Throwable] [message cause]
        (getStackTrace []
          stack-trace)))))

(deftest basic-exception-test
  (let [original (Exception. "foo")
        a (deserialize-exception (serialize-exception original))]
    (is (= "foo" (.getMessage a)))))

(deftest ex-data-test
  (let [original (ex-info "foo" {:a 1})
        a (deserialize-exception (serialize-exception original))]
    (is (= "foo" (.getMessage a)))
    (is (= {:a 1} (ex-data a)))))

(deftest cause-test
  (let [original (Exception. "foo" (Exception. "bar"))
        a (deserialize-exception (serialize-exception original))]
    (is (= "bar" (.getMessage (.getCause a))))))

(defn drop-first-line [s]
  (-> s
      (string/split #"\n")
      rest
      (->> (string/join "\n"))))

(deftest stack-trace-test
  ; First line differs as it contains the name of Exception class
  (let [original (Exception. "foo")
        a (deserialize-exception (serialize-exception original))]
    (is (= (drop-first-line (with-out-str (st/print-stack-trace original)))
           (drop-first-line (with-out-str (st/print-stack-trace a)))))))