Merge remote-tracking branch 'origin/stack-dispatch' into develop

Conflicts:
	src/re_frame/router.cljs

src/re_frame/events.cljs

@@ -95,5 +95,12 @@
       (if  *handling*
         (console :error "re-frame: while handling \""  *handling*  "\"  dispatch-sync was called for \"" event-v "\". You can't call dispatch-sync in an event handler.")
         (binding [*handling*  event-v]
-          (handler-fn app-db event-v))))))
+          (let [stack (some-> event-v
+                          meta
+                          :stack)]
+            (try
+              (handler-fn app-db event-v)
+              (catch :default e
+                (console :warn stack) ;; output a msg to help to track down dispatching point
+                (throw e)))))))))
 

src/re_frame/router.cljs

@@ -144,7 +144,7 @@
             [:paused :add-event] [:paused  #(-add-event this arg)]
             [:paused :resume   ] [:running #(-resume this)]
 
-            (throw (ex-info "re-frame: router state transition not found" {:fsm-state fsm-state :trigger trigger})))]
+            (throw (js/Error. (str "re-frame: router state transition not found. " fsm-state " " trigger))))]
 
       ;; The "case" above computed both the new FSM state, and the action. Now, make it happen.
       (set! fsm-state new-fsm-state)
@@ -219,9 +219,15 @@
   Usage example:
      (dispatch [:delete-item 42])"
   [event-v]
-  (if (nil? event-v)
-    (throw (ex-info "re-frame: you called \"dispatch\" without an event vector" {}))
-    (push event-queue event-v))
+  (let [stack  (->> (js/Error.
+                      (str "Error thrown in event handler " (first event-v)))
+                    .-stack
+                    clojure.string/split-lines
+                    (remove #(re-find #"react.inc.js|\(native\)" %))  ;; get rid of the react frames
+                    (clojure.string/join "\n"))]  ;; grab a stack here so that give it to events
+    (if (nil? event-v)
+      (throw (js/Error. "re-frame: you called \"dispatch\" without an event vector."))
+      (push event-queue (with-meta event-v {:stack stack}))))
   nil)                                           ;; Ensure nil return. See https://github.com/Day8/re-frame/wiki/Beware-Returning-False
 
 

test/re-frame/event_test.cljs

@@ -0,0 +1,30 @@
+(ns re-frame.event-test
+  (:require [cljs.test         :refer-macros [is deftest]]
+            [re-frame.db       :as db]
+            [re-frame.core     :as re-frame]))
+
+;=====test basic subscriptions  ======
+
+;; disabled as it doesn't really test anything
+#_(deftest test-event-def
+  "tests that an error thrown generates an informational warning"
+  (re-frame/clear-all-events!)
+
+  (re-frame/def-event
+    :test-event
+    (fn [db [event-kw stack]]
+      (throw (js/Error. "thrown in handler"))
+      db))
+
+  (defn test-fn1
+    []
+    (re-frame/dispatch [:test-event]))
+
+  (defn test-fn2
+    []
+    (test-fn1))
+
+  (test-fn2)
+  )
+
+