fix: Make background option work with grunt tasks written in CoffeeSc…

…ript

Use node's built-in message channel for the background server, allowing
only the modulePath argument to be passed to child_process.fork. This works
around an issue in CoffeeScript's interceptor, which doesn't support treating
args as an optional parameter, passing options as args and omitting options.

Closes #174

gruntfile.js

@@ -87,6 +87,16 @@ module.exports = function (grunt) {
           }
         ]
       },
+      background: {
+        background: true,
+        files: [
+          {
+            src: 'node_modules/expect.js/index.js'
+          }, {
+            src: 'test/**/*.js'
+          }
+        ]
+      },
       config: {
         configFile: 'karma.conf.js',
         singleRun: true
@@ -114,6 +124,11 @@ module.exports = function (grunt) {
       tests: {
         files: 'test/**/*.js',
         tasks: ['karma:dev:run']
+      },
+      bgtest: {
+        // This is just to stop node exiting
+        files: 'test/**/*.js',
+        tasks: []
       }
     }
   })
@@ -123,6 +138,7 @@ module.exports = function (grunt) {
 
   grunt.registerTask('test', ['karma:single', 'karma:config', 'karma:merge'])
   grunt.registerTask('default', ['eslint', 'test'])
+  grunt.registerTask('bgtest', ['karma:background', 'watch:bgtest'])
 
   grunt.registerTask('release', 'Bump the version and publish to npm.', function (type) {
     grunt.task.run([

lib/background.js

@@ -1,6 +1,6 @@
 var Server = require('karma').Server
-process.stdin.on('readable', function () {
-  var data = JSON.parse(process.stdin.read())
-  var server = new Server(data)
-  server.start(data)
+
+process.on('message', function (data) {
+  var server = new Server(data.config)
+  server.start()
 })

tasks/grunt-karma.js

@@ -112,10 +112,8 @@ module.exports = function (grunt) {
     // allow karma to be run in the background so it doesn't block grunt
     if (data.background) {
       var backgroundProcess = require('child_process').fork(
-          path.join(__dirname, '..', 'lib', 'background.js'),
-          { silent: true }
+          path.join(__dirname, '..', 'lib', 'background.js')
       )
-      backgroundProcess.stdin.write(JSON.stringify(data))
 
       backgroundProcess.on('close', function (code) {
         var error = code
@@ -128,6 +126,7 @@ module.exports = function (grunt) {
         backgroundProcess.kill()
       })
 
+      backgroundProcess.send({ config: data })
       done()
     } else {
       var server = new Server(data, finished.bind(done))