Use getOwnPropertyDescriptor to find getters

Author: corlaez

packages/node_modules/overmind/src/utils.ts

@@ -30,10 +30,16 @@ export const makeStringifySafeMutations = (mutations: IMutation[]) => {
 export function deepCopy(obj) {
   if (isPlainObject(obj)) {
     return Object.keys(obj).reduce((aggr: any, key) => {
-      if(obj.__lookupGetter__(key))
-        aggr.__defineGetter__(key, obj.__lookupGetter__(key))
-      else 
-        aggr[key] = deepCopy(obj[key])
+      const originalDescriptor = Object.getOwnPropertyDescriptor(obj, key)
+      const isAGetter = originalDescriptor && 'get' in originalDescriptor
+      const value = obj[key]
+
+      if (isPlainObject(value) && !isAGetter) {
+        aggr[key] = deepCopy(value)
+      } else {
+        Object.defineProperty(aggr, key, originalDescriptor as any)
+      }
+
       return aggr
     }, {})
   } else if (Array.isArray(obj)) {