[proposal] browserPolyfill option

README.md

@@ -51,3 +51,14 @@ var scriptTree = esTranspiler(inputTree, {
 ```
 
 `exportModuleMetadata` is an option that can be used to write a JSON file to the output tree that gives you metadata about the tree's imports and exports.
+
+## Polyfill
+
+In order to use some of the ES6 features you must include the Babel [polyfill](http://babeljs.io/docs/usage/polyfill/#usage-in-browser).
+
+You don't always need this, review which features need the polyfill here: [ES6 Features](https://babeljs.io/docs/learn-es6).
+
+```js
+var esTranspiler = require('broccoli-babel-transpiler');
+var scriptTree = esTranspiler(inputTree, { browserPolyfill: true });
+```

index.js

@@ -6,6 +6,8 @@ var clone      = require('clone');
 var path       = require('path');
 var fs         = require('fs');
 var stringify  = require('json-stable-stringify');
+var mergeTrees = require('broccoli-merge-trees');
+var funnel = require('broccoli-funnel');
 
 function getExtensionsRegex(extensions) {
   return extensions.map(function(extension) {
@@ -39,6 +41,18 @@ function Babel(inputTree, options) {
     // delete it from the options hash
     delete this.options.exportModuleMetadata;
   }
+
+  if (this.options.browserPolyfill) {
+    delete this.options.browserPolyfill;
+
+    var babelCorePath = require.resolve('babel-core');
+    babelCorePath = babelCorePath.replace(/\/babel-core\/.*$/, '/babel-core');
+
+    var polyfill = funnel(babelCorePath, { files: ['browser-polyfill.js'] });
+    this.inputTree = mergeTrees([polyfill, inputTree]);
+  } else {
+    this.inputTree = inputTree;
+  }
 }
 
 Babel.prototype = Object.create(Filter.prototype);

package.json

@@ -31,6 +31,8 @@
     "babel-core": "^5.0.0",
     "json-stable-stringify": "^1.0.0",
     "cauliflower-filter": "^1.0.4",
+    "broccoli-funnel": "^0.2.3",
+    "broccoli-merge-trees": "^0.2.1",
     "clone": "^0.2.0"
   },
   "devDependencies": {