Add importHelpers option

index.js

@@ -1,13 +1,96 @@
-var transform = require( 'babel-core' ).transform;
+var babelc = require('babel-core');
+var sander = require('sander');
+var mapSeries = require('promise-map-series');
+var assign = require('lodash/object/assign');
+var merge = require('lodash/object/merge');
+var path = require('path');
 
 module.exports = babel;
 
-function babel ( code, options ) {
-	options.sourceMap = options.sourceMap !== false;
-	return transform( code, options );
+function babel(inputdir, outputdir, opts) {
+	importHelpers = !!opts.importHelpers;
+	if (importHelpers) {
+		opts.externalHelpers = true;
+	}
+	delete opts.importHelpers;
+	return sander.lsr(inputdir).then(function(allFiles) {
+		allFiles = allFiles.filter(extFilter);
+		var usedHelpers = [];
+		return mapSeries(allFiles, function(filename) {
+			return sander.readFile(inputdir, filename).then(function(code) {
+				if (importHelpers) {
+					var hf = slashes(filename) + '__babelHelpers.js';
+					code = 'import {babelHelpers} from "' + hf + '";\n' + code;
+				}
+				var result = babelc.transform(code, assign({}, opts, {
+					filename: inputdir + '/' + filename
+				}));
+				if (importHelpers) {
+					addUniqueHelpers(usedHelpers, result.metadata.usedHelpers);
+				}
+				return sander.writeFile(outputdir, filename, result.code);
+			});
+		}).then(function() {
+			if (importHelpers) {
+				// NOTE: This is broken because .babelrc options wont be inherited
+				//       when building the helpers. This is because babel can
+				//       consider different options for different files transformed,
+				//       which is unfortunate because external babel helpers
+				//       won't be "correct" unless the same options are used
+				//       for every file. As a work around just copy options from
+				//       .babelrc into the gobblefile.
+				var code = buildHelpers(usedHelpers, opts);
+				return sander.writeFile(outputdir, '__babelHelpers.js', code);
+			}
+		});
+	});
+}
+
+function extFilter(filename) {
+	return /\.(js|es6)$/.test(filename)
+}
+
+function slashes(from) {
+	var count = from.split('/').length;
+	return count > 1 ? (new Array(count + 1)).join('../') : './';
+}
+
+function buildHelpers(usedHelpers, opts) {
+	var helpers1 = babelc.buildExternalHelpers(usedHelpers, "var");
+	opts = merge({}, opts, {
+		externalHelpers: true,
+		blacklist: ["strict", "es6.tailCall"]
+	}, mergeCustom);
+	addUniqueHelpers(usedHelpers,
+		babelc.transform(helpers1, opts).metadata.usedHelpers
+	);
+	var helpers2 = babelc.buildExternalHelpers(usedHelpers, "var");
+	return "export " + babelc.transform(helpers2, opts).code;
+}
+
+function mergeCustom(a, b) {
+	if (Array.isArray(a)) {
+		var c = a.slice(0);
+		for (var i = b.length - 1; i >= 0; i--) {
+			var v = b[i];
+			if (c.indexOf(v) < 0) {
+				c.push(v);
+			}
+		}
+		return c;
+	}
+}
+
+function addUniqueHelpers(dest, src) {
+	for (var i = src.length - 1; i >= 0; i--) {
+		if (dest.indexOf(src[i]) < 0) {
+			dest.push(src[i]);
+		}
+	}
 }
 
 babel.defaults = {
-	accept: [ '.js', '.es6' ],
-	ext: '.js'
+	accept: ['.js', '.es6'],
+	ext: '.js',
+	sourceMap: true
 };

package.json

@@ -6,7 +6,10 @@
   "license": "MIT",
   "repository": "https://github.com/babel/gobble-babel",
   "dependencies": {
-    "babel-core": "^5.0.0"
+    "babel-core": "^5.0.0",
+    "lodash": "^3.7.0",
+    "promise-map-series": "^0.2.1",
+    "sander": "^0.2.3"
   },
   "keywords": [
     "gobble"