merge resolve plugins just like config

.gitignore

@@ -43,3 +43,6 @@ jspm_packages
 
 # Webstorm project metadata
 .idea
+
+# macOS
+.DS_Store

src/Resolve.js

@@ -55,16 +55,21 @@ module.exports = class extends ChainedMap {
       'extensions',
       'mainFields',
       'mainFiles',
-      'modules',
-      'plugins',
+      'modules'
     ];
 
+    if (!omit.includes('plugin') && 'plugin' in obj) {
+      Object.keys(obj.plugin).forEach(name =>
+        this.plugin(name).merge(obj.plugin[name])
+      );
+    }
+
     omissions.forEach(key => {
       if (!omit.includes(key) && key in obj) {
         this[key].merge(obj[key]);
       }
     });
 
-    return super.merge(obj, [...omit, ...omissions]);
+    return super.merge(obj, [...omit, ...omissions, 'plugin']);
   }
 };

test/Resolve.js

@@ -1,6 +1,16 @@
 import test from 'ava';
 import Resolve from '../src/Resolve';
 
+class StringifyPlugin {
+  constructor(...args) {
+    this.values = args;
+  }
+
+  apply() {
+    return JSON.stringify(this.values);
+  }
+}
+
 test('is Chainable', t => {
   const parent = { parent: true };
   const resolve = new Resolve(parent);
@@ -123,3 +133,25 @@ test('plugin with name', t => {
 
   t.is(resolve.plugins.get('alpha').name, 'alpha');
 });
+
+
+test('plugin empty', t => {
+  const resolve = new Resolve();
+  const instance = resolve
+    .plugin('stringify')
+    .use(StringifyPlugin)
+    .end();
+
+  t.is(instance, resolve);
+  t.true(resolve.plugins.has('stringify'));
+  t.deepEqual(resolve.plugins.get('stringify').get('args'), []);
+});
+
+test('plugin with args', t => {
+  const resolve = new Resolve();
+
+  resolve.plugin('stringify').use(StringifyPlugin, ['alpha', 'beta']);
+
+  t.true(resolve.plugins.has('stringify'));
+  t.deepEqual(resolve.plugins.get('stringify').get('args'), ['alpha', 'beta']);
+});