Fix reg-global-interceptor code reloading

Fixes #655

Author: superstructor

src/re_frame/settings.cljc

@@ -17,15 +17,31 @@
   []
   (:loaded? @store))
 
+(defn -replace-global-interceptor
+  [global-interceptors interceptor]
+  (reduce
+    (fn [ret existing-interceptor]
+      (if (= (:id interceptor)
+             (:id existing-interceptor))
+        (do
+          (when interop/debug-enabled?
+            (when (not (loaded?))
+              (console :warn "re-frame: replacing duplicate global interceptor id: " (:id interceptor))))
+          (conj ret interceptor))
+        (conj ret existing-interceptor)))
+    interop/empty-queue
+    global-interceptors))
+
 (defn reg-global-interceptor
   [{:keys [id] :as interceptor}]
   (swap! store update :global-interceptors
          (fn [global-interceptors]
            (let [ids (map :id global-interceptors)]
-             (when interop/debug-enabled?
-               (when (and (not (loaded?)) (some #{id} ids))
-                 (console :warn "re-frame: duplicate global interceptor id: " id)))
-             (conj global-interceptors interceptor)))))
+             (if (some #{id} ids)
+               ;; If the id already exists we replace it in-place to maintain the ordering of
+               ;; global interceptors esp during hot-code reloading in development.
+               (-replace-global-interceptor global-interceptors interceptor)
+               (conj global-interceptors interceptor))))))
 
 (defn get-global-interceptors
   []