created mergedConfig getter to avoid obnoxious checks for undefined everywhere

src/modules/config.js

@@ -40,8 +40,27 @@ const defaultState = {
   minimalScopesMode: undefined // instance default
 }
 
+// caching the instance default properties
+export const instanceDefaultProperties = Object.entries(defaultState)
+  .filter(([key, value]) => value === undefined)
+  .map(([key, value]) => key)
+
 const config = {
   state: defaultState,
+  getters: {
+    mergedConfig (state, getters, rootState, rootGetters) {
+      const { instance } = rootState
+      return {
+        ...state,
+        ...instanceDefaultProperties
+          .map(key => [key, state[key] === undefined
+            ? instance[key]
+            : state[key]
+          ])
+          .reduce((acc, [key, value]) => ({ ...acc, [key]: value }), {})
+      }
+    }
+  },
   mutations: {
     setOption (state, { name, value }) {
       set(state, name, value)