feat: accept onStderrData callback

* chore: use cypress eslint dev rules

* feat: expose onStderrData callback

* fix: handle when xvfb closes with non zero exit code

* fix: eslint

* chore: add tests

* fix: link to circle

.eslintrc

@@ -0,0 +1,10 @@
+{
+  "extends": [
+    "plugin:cypress-dev/general",
+    "plugin:cypress-dev/tests"
+  ],
+  "env": {
+    "es6": true,
+    "node": true
+  }
+}

README.md

@@ -1,7 +1,7 @@
 @cypress/xvfb: easily start and stop an X Virtual Frame Buffer from your node apps.
 -----
 
-[![CircleCI](https://circleci.com/gh/cypress-io/node-xvfb.svg?style=svg)](https://circleci.com/gh/cypress-io/node-xvfb)
+[![CircleCI](https://circleci.com/gh/cypress-io/xvfb.svg?style=svg)](https://circleci.com/gh/cypress-io/xvfb)
 [![semantic-release](https://img.shields.io/badge/%20%20%F0%9F%93%A6%F0%9F%9A%80-semantic--release-e10079.svg)](https://github.com/semantic-release/semantic-release)
 
 ### Usage

index.js

@@ -1,28 +1,30 @@
 /* eslint-disable node/no-deprecated-api */
-var fs = require('fs')
-var path = require('path')
-var spawn = require('child_process').spawn
+const once = require('lodash.once')
+const fs = require('fs')
+const path = require('path')
+const spawn = require('child_process').spawn
 fs.exists = fs.exists || path.exists
 fs.existsSync = fs.existsSync || path.existsSync
 
 function Xvfb (options) {
   options = options || {}
-  this._display = (options.displayNum ? ':' + options.displayNum : null)
+  this._display = (options.displayNum ? `:${options.displayNum}` : null)
   this._reuse = options.reuse
   this._timeout = options.timeout || 500
   this._silent = options.silent
+  this._onStderrData = options.onStderrData || (() => {})
   this._xvfb_args = options.xvfb_args || []
 }
 
 Xvfb.prototype = {
-  start: function (cb) {
+  start (cb) {
     if (!this._process) {
-      var lockFile = this._lockFile()
+      let lockFile = this._lockFile()
 
       this._setDisplayEnvVariable()
 
       fs.exists(lockFile, function (exists) {
-        var didSpawnFail = false
+        let didSpawnFail = false
         try {
           this._spawnProcess(exists, function (e) {
             didSpawnFail = true
@@ -32,7 +34,7 @@ Xvfb.prototype = {
           return cb && cb(e)
         }
 
-        var totalTime = 0;
+        let totalTime = 0;
         (function checkIfStarted () {
           fs.exists(lockFile, function (exists) {
             if (didSpawnFail) {
@@ -56,13 +58,13 @@ Xvfb.prototype = {
     }
   },
 
-  stop: function (cb) {
+  stop (cb) {
     if (this._process) {
       this._killProcess()
       this._restoreDisplayEnvVariable()
 
-      var lockFile = this._lockFile()
-      var totalTime = 0;
+      let lockFile = this._lockFile()
+      let totalTime = 0;
       (function checkIfStopped () {
         fs.exists(lockFile, function (exists) {
           if (!exists) {
@@ -82,25 +84,26 @@ Xvfb.prototype = {
     }
   },
 
-  display: function () {
+  display () {
     if (!this._display) {
-      var displayNum = 98
-      var lockFile
+      let displayNum = 98
+      let lockFile
       do {
         displayNum++
         lockFile = this._lockFile(displayNum)
       } while (!this._reuse && fs.existsSync(lockFile))
-      this._display = ':' + displayNum
+      this._display = `:${displayNum}`
     }
+
     return this._display
   },
 
-  _setDisplayEnvVariable: function () {
+  _setDisplayEnvVariable () {
     this._oldDisplay = process.env.DISPLAY
     process.env.DISPLAY = this.display()
   },
 
-  _restoreDisplayEnvVariable: function () {
+  _restoreDisplayEnvVariable () {
     // https://github.com/cypress-io/xvfb/issues/1
     // only reset truthy backed' up values
     if (this._oldDisplay) {
@@ -112,35 +115,52 @@ Xvfb.prototype = {
     }
   },
 
-  _spawnProcess: function (lockFileExists, onAsyncSpawnError) {
-    var display = this.display()
+  _spawnProcess (lockFileExists, onAsyncSpawnError) {
+    const onError = once(onAsyncSpawnError)
+
+    let display = this.display()
     if (lockFileExists) {
       if (!this._reuse) {
-        throw new Error('Display ' + display + ' is already in use and the "reuse" option is false.')
+        throw new Error(`Display ${display} is already in use and the "reuse" option is false.`)
       }
     } else {
-      this._process = spawn('Xvfb', [ display ].concat(this._xvfb_args))
+      const stderr = []
+
+      this._process = spawn('Xvfb', [display].concat(this._xvfb_args))
       this._process.stderr.on('data', function (data) {
-        if (!this._silent) {
-          process.stderr.write(data)
+        stderr.push(data.toString())
+
+        if (this._silent) {
+          return
         }
+
+        this._onStderrData(data)
       }.bind(this))
+
+      this._process.on('close', (code) => {
+        if (code !== 0) {
+          const err = new Error(`${stderr.join('\n')}`)
+          err.nonZeroExitCode = true
+          onError(err)
+        }
+      })
+
       // Bind an error listener to prevent an error from crashing node.
       this._process.once('error', function (e) {
-        onAsyncSpawnError(e)
+        onError(e)
       })
     }
   },
 
-  _killProcess: function () {
+  _killProcess () {
     this._process.kill()
     this._process = null
   },
 
-  _lockFile: function (displayNum) {
+  _lockFile (displayNum) {
     displayNum = displayNum || this.display().toString().replace(/^:/, '')
-    return '/tmp/.X' + displayNum + '-lock'
-  }
+    return `/tmp/.X${displayNum}-lock`
+  },
 }
 
 module.exports = Xvfb

package.json

@@ -10,16 +10,22 @@
   "repository": {
     "url": "https://github.com/cypress-io/xvfb"
   },
-  "dependencies": {},
+  "dependencies": {
+    "lodash.once": "^4.1.1"
+  },
   "license": "MIT",
   "scripts": {
-    "test": "standard --fix --verbose *.js && mocha",
+    "test": "eslint **/*.js && mocha",
+    "test-watch": "mocha watch",
     "semantic-release": "semantic-release pre && npm publish --access public && semantic-release post",
     "commit": "commit-wizard"
   },
   "devDependencies": {
     "chai": "^4.1.2",
     "condition-circle": "^1.5.0",
+    "eslint": "^4.13.1",
+    "eslint-plugin-cypress-dev": "^1.1.2",
+    "eslint-plugin-mocha": "^4.11.0",
     "mocha": "^3.5.0",
     "pre-git": "^3.15.0",
     "semantic-release": "^6.3.6",

test/xvfb_spec.js

@@ -2,13 +2,31 @@ const { expect } = require('chai')
 
 const Xvfb = require('../')
 
-describe('xvfb', function(){
-  beforeEach(function(){
-    this.xvfb = new Xvfb()
+describe('xvfb', function () {
+  context('onStderrData', function () {
+    it('accepts callback function', function () {
+      const cb = () => {}
+
+      const xvfb = new Xvfb({
+        onStderrData: cb,
+      })
+
+      expect(xvfb._onStderrData).to.eq(cb)
+    })
+
+    it('sets default function otherwise', function () {
+      const xvfb = new Xvfb()
+
+      expect(xvfb._onStderrData).to.be.a('function')
+    })
   })
 
-  context('issue: #1', function(){
-    it('issue #1: does not mutate process.env.DISPLAY', function(){
+  context('issue: #1', function () {
+    beforeEach(function () {
+      this.xvfb = new Xvfb()
+    })
+
+    it('issue #1: does not mutate process.env.DISPLAY', function () {
       delete process.env.DISPLAY
 
       expect(process.env.DISPLAY).to.be.undefined