[Fix #359] Workaround the transit-cljs map entry issue

See also cognitect/transit-cljs#42.

src/cljs/snapshot/lumo/common.cljs

@@ -8,14 +8,25 @@
 
 (def ^:private ^:const JSON_EXT ".json")
 
+(def read-opts
+  {"cljs/MapEntry" (transit/read-handler (fn [[k v]] (MapEntry. k v nil)))})
+
 (defn transit-json->cljs
   [json]
-  (let [rdr (transit/reader :json)]
+  (let [rdr (transit/reader :json read-opts)]
     (transit/read rdr json)))
 
+;; the read-opts and write-opts maps are necessary because of:
+;; https://github.com/cognitect/transit-cljs/issues/33
+(def write-opts
+  {cljs.core/MapEntry
+   (transit/write-handler
+    (fn [_] "cljs/MapEntry")
+    (fn [entry] [(-key entry) (-val entry)]))})
+
 (defn cljs->transit-json
   [x]
-  (let [wtr (transit/writer :json)]
+  (let [wtr (transit/writer :json write-opts)]
     (transit/write wtr x)))
 
 (defn- load-core-analysis-cache