Drop node 4 support and modernize the codebase

.travis.yml

@@ -2,7 +2,6 @@ language: node_js
 node_js:
 - '8'
 - '6'
-- '4'
 branches:
   only:
   - master

lib/grunt/index.js

@@ -26,14 +26,12 @@
 
 'use strict';
 
-module.exports = function(grunt, extraArguments) {
-  var chalk = require('chalk');
-  var VinylStream = require('./vinyl-stream');
-  var fs = require('fs');
-  var path = require('path');
-  var gulpCompiler = require('../gulp')({extraArguments: extraArguments});
-  var Transform = require('stream').Transform;
-  var gulpCompilerOptions = {
+module.exports = (grunt, extraArguments) => {
+  const chalk = require('chalk');
+  const VinylStream = require('./vinyl-stream');
+  const gulpCompiler = require('../gulp')({extraArguments: extraArguments});
+  const Transform = require('stream').Transform;
+  const gulpCompilerOptions = {
     streamMode: 'IN',
     logger: grunt.log,
     pluginName: 'grunt-google-closure-compiler',
@@ -46,7 +44,7 @@ module.exports = function(grunt, extraArguments) {
    * @return {Promise}
    */
   function compilationPromise(files, options) {
-    var hadError = false;
+    let hadError = false;
     function logFile(cb) {
       // If an error was encoutered, it will have already been logged
       if (!hadError) {
@@ -59,14 +57,14 @@ module.exports = function(grunt, extraArguments) {
       cb();
     }
 
-    var loggingStream = new Transform({
+    const loggingStream = new Transform({
       objectMode: true,
       transform: function() {},
       flush: logFile
     });
 
     return new Promise(function(resolve, reject) {
-      var stream;
+      let stream;
       if (files) {
         // Source files were provided by grunt. Read these
         // in to a stream of vinyl files and pipe them through
@@ -95,16 +93,16 @@ module.exports = function(grunt, extraArguments) {
   }
 
   function closureCompilerGruntTask() {
-    var taskObject = this;
-    var asyncDone = this.async();
-    var compileTasks = [];
+    const taskObject = this;
+    const asyncDone = this.async();
+    const compileTasks = [];
 
     function getCompilerOptions() {
-      var opts = taskObject.options({
+      const opts = taskObject.options({
         args: undefined
       });
 
-      var args = opts.args;
+      const args = opts.args;
 
       delete opts.args;
 
@@ -116,9 +114,9 @@ module.exports = function(grunt, extraArguments) {
 
     // Invoke the compiler once for each set of source files
     taskObject.files.forEach(function (f) {
-      var options = getCompilerOptions();
+      const options = getCompilerOptions();
 
-      var src = f.src.filter(function (filepath) {
+      const src = f.src.filter(filepath => {
         if (!grunt.file.exists(filepath)) {
           grunt.log.warn('Source file ' + chalk.cyan(filepath) + ' not found');
           return false;
@@ -144,18 +142,18 @@ module.exports = function(grunt, extraArguments) {
     // If the task was invoked without any files provided by grunt, assume that
     // --js flags are present and we want to run the compiler anyway.
     if (taskObject.files.length === 0) {
-      var options = getCompilerOptions();
+      const options = getCompilerOptions();
       compileTasks.push(compilationPromise(null, options.args || options.compilerOpts));
     }
 
     // Multiple invocations of the compiler can occur for a single task target. Wait until
     // they are all completed before calling the "done" method.
-    Promise.all(compileTasks).then(function () {
-      asyncDone();
-    }, function () {
-      grunt.fail.warn('Compilation error');
-      asyncDone();
-    });
+    Promise.all(compileTasks)
+      .then(() => asyncDone())
+      .catch(() => {
+        grunt.fail.warn('Compilation error');
+        asyncDone();
+      });
   }
 
   grunt.registerMultiTask('closure-compiler',

lib/grunt/vinyl-stream.js

@@ -22,51 +22,52 @@
  */
 'use strict';
 
-var fs = require('fs');
-var path = require('path');
-var Readable = require('stream').Readable;
-var File = require('vinyl');
+const fs = require('fs');
+const path = require('path');
+const Readable = require('stream').Readable;
+const File = require('vinyl');
 
-function VinylStream(files, opts) {
-  Readable.call(this, {objectMode: true});
-  this._base = path.resolve(opts.base || process.cwd());
-  this._files = files.slice();
-  this.resume();
-}
-VinylStream.prototype = Object.create(Readable.prototype);
-
-VinylStream.prototype._read = function() {
-  if (this._files.length === 0) {
-    this.emit('end');
-    return;
+class VinylStream extends Readable {
+  constructor(files, opts) {
+    super({objectMode: true});
+    this._base = path.resolve(opts.base || process.cwd());
+    this._files = files.slice();
+    this.resume();
   }
-  this.readFile();
-};
 
-VinylStream.prototype.readFile = function() {
-  if (this._files.length === 0) {
-    return;
-  }
-  var filepath = this._files.shift();
-  var fullpath = path.resolve(this._base, filepath);
-  fs.readFile(fullpath, (function (fullpath, err, data) {
-    if (err) {
-      this.emit('error', err);
+  _read() {
+    if (this._files.length === 0) {
+      this.emit('end');
       return;
     }
+    this.readFile();
+  }
 
-    var file = new File({
-      base: this._base,
-      path: fullpath,
-      contents: data
-    });
-
-    if (!this.push(file)) {
+  readFile() {
+    if (this._files.length === 0) {
       return;
-    } else {
-      this.readFile();
     }
-  }).bind(this, fullpath));
-};
+    const filepath = this._files.shift();
+    const fullpath = path.resolve(this._base, filepath);
+    fs.readFile(fullpath, (err, data) => {
+      if (err) {
+        this.emit('error', err);
+        return;
+      }
+
+      const file = new File({
+        base: this._base,
+        path: fullpath,
+        contents: data
+      });
+
+      if (!this.push(file)) {
+        return;
+      } else {
+        this.readFile();
+      }
+    });
+  }
+}
 
 module.exports = VinylStream;

lib/gulp/concat-to-json.js

@@ -24,7 +24,7 @@
 'use strict';
 
 function json_file(src, path, source_map) {
-  var filejson = {
+  const filejson = {
     src: src
   };
 
@@ -43,10 +43,10 @@ function json_file(src, path, source_map) {
  * @param {Array<Object>} files
  * @return {string}
  */
-module.exports = function(files) {
-  var path = require('path');
-  var jsonFiles = [];
-  for (var i = 0; i < files.length; i++) {
+module.exports = files => {
+  const path = require('path');
+  const jsonFiles = [];
+  for (let i = 0; i < files.length; i++) {
     jsonFiles.push(
         json_file(files[i].contents.toString(), files[i].relative || path.relative(process.cwd(), files[i].path),
             files[i].sourceMap ? JSON.stringify(files[i].sourceMap) : undefined));