parallelizing file existance check using promises

jingo

@@ -15,6 +15,7 @@ var fs = require('fs')
 var os = require('os')
 var semver = require('semver')
 var pkg = require('./package')
+var fileExists = require('./lib/file_exists')
 
 global.Git = require('./lib/gitmech')
 
@@ -35,7 +36,7 @@ if (program.hashString) {
   process.exit(0)
 }
 
-if (!program.config || !fs.existsSync(program.config)) {
+if (!program.config || !fileExists.sync(program.config)) {
   program.help()
   process.exit(-1)
 }

lib/components.js

@@ -4,6 +4,7 @@ var models = require('./models')
 var Promiser = require('bluebird')
 var renderer = require('./renderer')
 var Configurable = require('./configurable')
+var fileExists = require('./file_exists')
 
 models.use(Git)
 
@@ -34,7 +35,7 @@ Component.prototype.exists = function () {
     return this._exists
   }
 
-  this._exists = fs.existsSync(Git.absPath(this.file))
+  this._exists = fileExists.sync(Git.absPath(this.file))
 
   if (!this._exists) {
     this.cache = null

lib/file_exists.js

@@ -0,0 +1,30 @@
+var fs = require('fs')
+var Promiser = require('bluebird')
+// using fs.access instead of the deprecated fs.exists:
+// https://nodejs.org/api/fs.html#fs_fs_exists_path_callback
+var exists = Promiser.promisify(fs.access)
+
+module.exports = {
+  sync: function (file) {
+    try {
+      fs.accessSync(file)
+      // If it didn't throw, the file exists
+      return true
+    } catch (err) {
+      return catchEnoent(err)
+    }
+  },
+  async: function (file) {
+    return exists(file)
+    .then(function (res) { return true })
+    .catch(catchEnoent)
+  }
+}
+
+function catchEnoent (err) {
+  if (err.code === 'ENOENT') {
+    return false
+  } else {
+    throw err
+  }
+}

lib/models.js

@@ -4,6 +4,7 @@ var namer = require('./namer')
 var fs = require('fs')
 var Configurable = require('./configurable')
 var locker = require('./locker')
+var fileExists = require('./file_exists')
 
 var gitmech
 
@@ -61,7 +62,7 @@ Page.prototype.renameTo = function (newName) {
 
   return new Promiserr(function (resolve, reject) {
     // Cannot rename if the file already exists
-    if (fs.existsSync(gitmech.absPath(newFilename))) {
+    if (fileExists.sync(gitmech.absPath(newFilename))) {
       reject()
       return
     }

routes/misc.js

@@ -1,8 +1,9 @@
 /* global Git */
 var router = require('express').Router()
 var renderer = require('../lib/renderer')
-var fs = require('fs')
 var models = require('../lib/models')
+var Promiser = require('bluebird')
+var fileExists = require('../lib/file_exists')
 
 models.use(Git)
 
@@ -22,24 +23,23 @@ function _postPreview (req, res) {
 
 function _getExistence (req, res) {
   if (!req.query.data) {
-    res.send(JSON.stringify({data: []}))
+    res.json({data: []})
     return
   }
 
   var result = []
-  var page
-  var n = req.query.data.length
-
-  req.query.data.forEach(function (pageName, idx) {
-    (function (name, index) {
-      page = new models.Page(name)
-      if (!fs.existsSync(page.pathname)) {
-        result.push(name)
-      }
-      if (index === (n - 1)) {
-        res.send(JSON.stringify({data: result}))
+
+  Promiser.all(req.query.data.map(function (pageName) {
+    var page = new models.Page(pageName)
+    return fileExists.async(page.pathname)
+    .then(function (exists) {
+      if (!exists) {
+        result.push(pageName)
       }
-    }(pageName, idx))
+    })
+  }))
+  .then(function () {
+    res.json({data: result})
   })
 }