Compile babel files in place during compile task

build/Gruntfile.coffee

@@ -1,6 +1,8 @@
 fs = require 'fs'
 path = require 'path'
 os = require 'os'
+glob = require 'glob'
+usesBabel = require './lib/uses-babel'
 
 # Add support for obselete APIs of vm module so we can make some third-party
 # modules work under node v0.11.x.
@@ -15,6 +17,7 @@ packageJson = require '../package.json'
 _.extend(global, require('harmony-collections')) unless global.WeakMap?
 
 module.exports = (grunt) ->
+  grunt.loadNpmTasks('grunt-babel')
   grunt.loadNpmTasks('grunt-coffeelint')
   grunt.loadNpmTasks('grunt-lesslint')
   grunt.loadNpmTasks('grunt-cson')
@@ -77,6 +80,11 @@ module.exports = (grunt) ->
       dest: appDir
       ext: '.js'
 
+  babelConfig =
+    options: {}
+    dist:
+      files: []
+
   lessConfig =
     options:
       paths: [
@@ -141,6 +149,13 @@ module.exports = (grunt) ->
 
       pegConfig.glob_to_multiple.src.push("#{directory}/lib/*.pegjs")
 
+      for jsFile in glob.sync("#{directory}/lib/**/*.js")
+        if usesBabel(jsFile)
+          babelConfig.dist.files.push({
+            src: [jsFile]
+            dest: jsFile
+          })
+
   grunt.initConfig
     pkg: grunt.file.readJSON('package.json')
 
@@ -148,6 +163,8 @@ module.exports = (grunt) ->
 
     docsOutputDir: 'docs/output'
 
+    babel: babelConfig
+
     coffee: coffeeConfig
 
     less: lessConfig
@@ -229,7 +246,7 @@ module.exports = (grunt) ->
           stderr: false
           failOnError: false
 
-  grunt.registerTask('compile', ['coffee', 'prebuild-less', 'cson', 'peg'])
+  grunt.registerTask('compile', ['babel', 'coffee', 'prebuild-less', 'cson', 'peg'])
   grunt.registerTask('lint', ['coffeelint', 'csslint', 'lesslint'])
   grunt.registerTask('test', ['shell:kill-atom', 'run-specs'])
 

build/lib/uses-babel.coffee

@@ -0,0 +1,18 @@
+fs = require 'fs'
+
+BABEL_PREFIXES = [
+	"'use babel'"
+	'"use babel"'
+	'/** use babel */'
+].map(Buffer)
+
+PREFIX_LENGTH = Math.max(BABEL_PREFIXES.map((prefix) -> prefix.length)...)
+
+buffer = Buffer(PREFIX_LENGTH)
+
+module.exports = (filename) ->
+  file = fs.openSync(filename, 'r')
+  fs.readSync(file, buffer, 0, PREFIX_LENGTH)
+  fs.closeSync(file)
+  BABEL_PREFIXES.some (prefix) ->
+    prefix.equals(buffer.slice(0, prefix.length))

build/package.json

@@ -12,8 +12,9 @@
     "formidable": "~1.0.14",
     "fs-plus": "2.x",
     "github-releases": "~0.2.0",
+    "glob": "^5.0.14",
     "grunt": "~0.4.1",
-    "grunt-electron-installer": "^0.37.0",
+    "grunt-babel": "^5.0.1",
     "grunt-cli": "~0.1.9",
     "grunt-coffeelint": "git+https://github.com/atom/grunt-coffeelint.git#cfb99aa99811d52687969532bd5a98011ed95bfe",
     "grunt-contrib-coffee": "~0.12.0",
@@ -21,6 +22,7 @@
     "grunt-contrib-less": "~0.8.0",
     "grunt-cson": "0.14.0",
     "grunt-download-atom-shell": "~0.14.0",
+    "grunt-electron-installer": "^0.37.0",
     "grunt-lesslint": "0.17.0",
     "grunt-peg": "~1.1.0",
     "grunt-shell": "~0.3.1",