Use object.fromentries; fix multiple concats

lib/util/Components.js

@@ -699,8 +699,10 @@ function componentRule(rule, context) {
   const updatedRuleInstructions = util._extend({}, ruleInstructions);
   const propTypesInstructions = propTypes(context, components, utils);
   const defaultPropsInstructions = defaultProps(context, components, utils);
-  const allKeys = new Set(Object.keys(detectionInstructions).concat(Object.keys(propTypesInstructions))
-    .concat(Object.keys(defaultPropsInstructions)));
+  const allKeys = new Set(Object.keys(detectionInstructions).concat(
+    Object.keys(propTypesInstructions),
+    Object.keys(defaultPropsInstructions)
+  ));
   allKeys.forEach(instruction => {
     updatedRuleInstructions[instruction] = function(node) {
       if (instruction in detectionInstructions) {

lib/util/defaultProps.js

@@ -3,6 +3,7 @@
  */
 'use strict';
 
+const fromEntries = require('object.fromentries');
 const astUtil = require('./ast');
 const propsUtil = require('./props');
 const variableUtil = require('./variable');
@@ -85,10 +86,11 @@ module.exports = function defaultPropsInstructions(context, components, utils) {
     }
 
     const defaults = component.defaultProps || {};
-    const newDefaultProps = defaultProps.reduce((acc, prop) => {
-      acc[prop.name] = prop;
-      return acc;
-    }, Object.assign({}, defaults));
+    const newDefaultProps = Object.assign(
+      {},
+      defaults,
+      fromEntries(defaultProps.map(prop => [prop.name, prop]))
+    );
 
     components.set(component.node, {
       defaultProps: newDefaultProps

package.json

@@ -28,6 +28,7 @@
     "doctrine": "^2.1.0",
     "has": "^1.0.3",
     "jsx-ast-utils": "^2.0.1",
+    "object.fromentries": "^2.0.0",
     "prop-types": "^15.6.2"
   },
   "devDependencies": {