[resolvers] [*] [fix] restore node 6 compatibility

See 69fce5c and 8c155ba#r123814192

Author: ljharb

.eslintrc

@@ -189,37 +189,17 @@
                 "no-console": "off",
             },
         },
-        {
-            "files": "resolvers/**",
-            "env": {
-                "es6": false,
-            },
-        },
-        {
-            "files": "resolvers/webpack/**",
-            "rules": {
-                "no-console": 1,
-                "prefer-template": 0,
-                "prefer-object-spread": 0,
-                "prefer-rest-params": 0,
-            },
-            "env": {
-                "es6": true,
-            },
-        },
         {
             "files": [
-                "resolvers/*/test/**/*",
+                "resolvers/**",
+                "utils/**",
             ],
             "env": {
-                "mocha": true,
-                "es6": false
+                "es6": false,
             },
-        },
-        {
-            "files": "utils/**",
             "parserOptions": {
-                "ecmaVersion": 6,
+                "sourceType": "module",
+                "ecmaVersion": 2016,
             },
             "rules": {
                 "comma-dangle": ["error", {
@@ -229,11 +209,31 @@
                     "exports": "always-multiline",
                     "functions": "never"
                 }],
+                "prefer-destructuring": "warn",
                 "prefer-object-spread": "off",
+                "prefer-rest-params": "off",
+                "prefer-spread": "warn",
                 "prefer-template": "off",
+            }
+        },
+        {
+            "files": [
+                "resolvers/webpack/**",
+                "utils/**",
+            ],
+            "rules": {
                 "no-console": 1,
             },
         },
+        {
+            "files": [
+                "resolvers/*/test/**/*",
+            ],
+            "env": {
+                "mocha": true,
+                "es6": false
+            },
+        },
         {
             "files": "tests/**",
             "env": {

resolvers/node/index.js

@@ -29,14 +29,14 @@ exports.resolve = function (source, file, config) {
 };
 
 function opts(file, config, packageFilter) {
-  return { // more closely matches Node (#333)
+  return Object.assign({ // more closely matches Node (#333)
     // plus 'mjs' for native modules! (#939)
     extensions: ['.mjs', '.js', '.json', '.node'],
-    ...config,
+  }, config, {
     // path.resolve will handle paths relative to CWD
     basedir: path.dirname(path.resolve(file)),
     packageFilter,
-  };
+  });
 }
 
 function identity(x) { return x; }

resolvers/webpack/index.js

@@ -270,18 +270,18 @@ function createWebpack1ResolveSync(webpackRequire, resolveConfig, plugins) {
     makeRootPlugin(ModulesInRootPlugin, 'module', resolveConfig.root),
     new ModulesInDirectoriesPlugin(
       'module',
-      resolveConfig.modulesDirectories || resolveConfig.modules || ['web_modules', 'node_modules'],
+      resolveConfig.modulesDirectories || resolveConfig.modules || ['web_modules', 'node_modules']
     ),
     makeRootPlugin(ModulesInRootPlugin, 'module', resolveConfig.fallback),
     new ModuleAsFilePlugin('module'),
     new ModuleAsDirectoryPlugin('module'),
     new DirectoryDescriptionFilePlugin(
       'package.json',
-      ['module', 'jsnext:main'].concat(resolveConfig.packageMains || webpack1DefaultMains),
+      ['module', 'jsnext:main'].concat(resolveConfig.packageMains || webpack1DefaultMains)
     ),
     new DirectoryDefaultFilePlugin(['index']),
     new FileAppendPlugin(resolveConfig.extensions || ['', '.webpack.js', '.web.js', '.js']),
-    new ResultSymlinkPlugin(),
+    new ResultSymlinkPlugin()
   );
 
   const resolvePlugins = [];
@@ -419,7 +419,7 @@ function findConfigPath(configPath, packageDir) {
       }
 
       const maybePath = path.resolve(
-        path.join(packageDir, 'webpack.config' + maybeExtension),
+        path.join(packageDir, 'webpack.config' + maybeExtension)
       );
       if (fs.existsSync(maybePath)) {
         configPath = maybePath;