Ensure babel extends builtins on jsnext build

.babelrc

@@ -1,17 +1,3 @@
 {
-  "presets": [
-    "es2015"
-  ],
-  "plugins": [
-    "add-module-exports",
-    [
-      "babel-plugin-transform-builtin-extend",
-      {
-        "globals": [
-          "Error"
-        ],
-        "approximate": true
-      }
-    ]
-  ]
+  "presets": "./babel-config.js"
 }

babel-config.js

@@ -0,0 +1,29 @@
+'use strict';
+
+var plugins = [
+  [
+    "babel-plugin-transform-builtin-extend",
+    {
+      "globals": ["Error"],
+      "approximate": true
+    }
+  ]
+];
+
+var env = process.env.BABEL_ENV || process.env.NODE_ENV;
+
+var modules;
+
+if (env === 'es') {
+  modules = false;
+} else {
+  modules = 'commonjs';
+  plugins.push('add-module-exports');
+}
+
+module.exports = {
+  "presets": [
+    ["es2015", { modules: modules }]
+  ],
+  "plugins": plugins
+};

lib/index.js

@@ -76,4 +76,4 @@ var ExtendableError = function (_extendableBuiltin2) {
 }(_extendableBuiltin(Error));
 
 exports.default = ExtendableError;
-module.exports = exports['default'];
+module.exports = exports['default'];

lib/index.jsnext.js

@@ -4,8 +4,31 @@ function _possibleConstructorReturn(self, call) { if (!self) { throw new Referen
 
 function _inherits(subClass, superClass) { if (typeof superClass !== "function" && superClass !== null) { throw new TypeError("Super expression must either be null or a function, not " + typeof superClass); } subClass.prototype = Object.create(superClass && superClass.prototype, { constructor: { value: subClass, enumerable: false, writable: true, configurable: true } }); if (superClass) Object.setPrototypeOf ? Object.setPrototypeOf(subClass, superClass) : subClass.__proto__ = superClass; }
 
-var ExtendableError = function (_Error) {
-  _inherits(ExtendableError, _Error);
+function _extendableBuiltin(cls) {
+  function ExtendableBuiltin() {
+    cls.apply(this, arguments);
+  }
+
+  ExtendableBuiltin.prototype = Object.create(cls.prototype, {
+    constructor: {
+      value: cls,
+      enumerable: false,
+      writable: true,
+      configurable: true
+    }
+  });
+
+  if (Object.setPrototypeOf) {
+    Object.setPrototypeOf(ExtendableBuiltin, cls);
+  } else {
+    ExtendableBuiltin.__proto__ = cls;
+  }
+
+  return ExtendableBuiltin;
+}
+
+var ExtendableError = function (_extendableBuiltin2) {
+  _inherits(ExtendableError, _extendableBuiltin2);
 
   function ExtendableError() {
     var message = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : '';
@@ -44,6 +67,6 @@ var ExtendableError = function (_Error) {
   }
 
   return ExtendableError;
-}(Error);
+}(_extendableBuiltin(Error));
 
-export default ExtendableError;
+export default ExtendableError;

package.json

@@ -7,7 +7,9 @@
   "typings": "./lib/index.d.ts",
   "scripts": {
     "test": "mocha --compilers js:babel-core/register --recursive",
-    "build": "node build.js",
+    "build": "npm run build:commonjs && npm run build:es",
+    "build:commonjs": "cross-env BABEL_ENV=commonjs babel src/index.js --out-file lib/index.js",
+    "build:es": "cross-env BABEL_ENV=es babel src/index.js --out-file lib/index.jsnext.js",
     "prepublish": "npm run build && npm run test"
   },
   "repository": {
@@ -32,6 +34,7 @@
     "babel-plugin-transform-builtin-extend": "^1.1.0",
     "babel-preset-es2015": "^6.6.0",
     "chai": "^3.2.0",
+    "cross-env": "^3.1.3",
     "mocha": "^2.4.5"
   },
   "dependencies": {}