refactor: move babel defaults value to Options.defaults

lib/builder/builder.js

@@ -177,14 +177,7 @@ module.exports = class Builder {
   }
 
   getBabelOptions({ isServer }) {
-    const options = _.defaults(
+    const options = _.clone(this.options.build.babel)
-      {},
-      this.options.build.babel,
-      {
-        babelrc: false,
-        cacheDirectory: !!this.options.dev
-      }
-    )
 
     if (typeof options.presets === 'function') {
       options.presets = options.presets({ isServer })

lib/common/options.js

@@ -119,6 +119,11 @@ Options.from = function (_options) {
     options.build.cssSourceMap = options.dev
   }
 
+  // babel cacheDirectory
+  if (options.build.babel.cacheDirectory === undefined) {
+    options.build.babel.cacheDirectory = options.dev
+  }
+
   // Debug errors
   if (options.debug === undefined) {
     options.debug = options.dev
@@ -210,7 +215,9 @@ Options.defaults = {
     styleResources: {},
     vendor: [],
     plugins: [],
-    babel: {},
+    babel: {
+      babelrc: false
+    },
     postcss: {},
     templates: [],
     watch: [],