Get logging working

src/re_frame/utils.cljs

@@ -1,34 +1,40 @@
-(ns re-frame.utils)
+(ns re-frame.utils
+  (:require
+    [clojure.set   :refer [difference]]))
 
 
 ;; -- Logging -----------------------------------------------------------------
 ;;
-;; re-frame uses various kinds of logging.
-;; Call set-loggers! if you want to override what it uses.
+;; re-frame internally uses a set of logging functions which, by default,
+;; print to js/console.
+;; Use set-loggers! if you want to change this default behaviour.
+;; In production environment, you may want to capture exceptions and POST
+;; them somewhere.  to , you might want to override the way that exceptions are
+;; handled by overridding "error"
 ;;
 (def default-loggers
-  {:log       js/console.log
-   :warn      js/console.warn
-   :error     js/console.error
-   :group     (or js/console.group js/console.log)    ;; group does not exist  < IE 11
-   :groupEnd  (or js/console.groupEnd #())})          ;; groupEnd does not exist  < IE 11
+  {:log       #(.log js/console %)
+   :warn      #(.warn js/console %)
+   :error     #(.error js/console %)
+   :group     #(if (.group js/console) (.group js/console %) (.log js/console %))  ;; group does not exist  < IE 11
+   :groupEnd  #(when (.groupEnd js/console) (.groupEnd js/console))})              ;; groupEnd does not exist  < IE 11
 
 ;; holds the current set of loggers.
 (def loggers (atom default-loggers))
 
 (defn set-loggers!
-  "new-loggers should be a map which looks like default-loggers"
+  "Change the set (subset?) of logging functions used by re-frame.
+  'new-loggers' should be a map which looks like default-loggers"
   [new-loggers]
-  (assert  (empty? (clojure.set/difference (set (keys new-loggers)) (set (keys default-loggers)))) "Unknown keys in new-loggers")
+  (assert  (empty? (difference (set (keys new-loggers)) (set (keys default-loggers)))) "Unknown keys in new-loggers")
   (swap! loggers merge new-loggers))
 
 
-(defn log      [& args] ({:log loggers}      (apply str args)))
-(defn warn     [& args] ({:warn loggers}     (apply str args)))
-(defn error    [& args] ({:error loggers}    (apply str args)))
-(defn group    [& args] ({:group loggers}    (apply str args)))
-(defn groupEnd [& args] ({:groupEnd loggers} (apply str args)))
-
+(defn log      [& args] ((:log @loggers)      (apply str args)))
+(defn warn     [& args] ((:warn @loggers)     (apply str args)))
+(defn group    [& args] ((:group @loggers)    (apply str args)))
+(defn groupEnd [& args] ((:groupEnd @loggers) (apply str args)))
+(defn error    [& args] ((:error @loggers)    (apply str args)))
 
 ;; -- Misc --------------------------------------------------------------------
 
@@ -36,5 +42,5 @@
   [v]
   (if (vector? v)
     (first v)
-    (warn "re-frame: expected a vector event, but got: " v)))
+    (error "re-frame: expected a vector event, but got: " v)))