Verify files have BOM during publish task

This verification is designed to simulate part of the Windows App
Certification Kit test.

Protects us from regressing winjs/winjs#1315 in the future.

Gruntfile.js

@@ -22,6 +22,8 @@ module.exports = function(grunt) {
 
     var currentGitCommitHash = execSync('git rev-parse HEAD').toString().trim();
 
+    var bomGlob = "**/*.+(js|css|htm|html)";
+
     // Project configuration.
     grunt.initConfig({
         pkg: pkg,
@@ -58,6 +60,22 @@ module.exports = function(grunt) {
             }
         },
 
+        "check-bom": {
+            publish: {
+                files: [{
+                    cwd: "js",
+                    src: bomGlob,
+                    expand: true,
+                    nocase: true
+                }, {
+                    cwd: publishRoot,
+                    src: bomGlob,
+                    expand: true,
+                    nocase: true
+                }]
+            }
+        },
+
         nugetpack: {
             publish: {
                 src: 'Knockout.WinJS.nuspec',
@@ -104,6 +122,8 @@ module.exports = function(grunt) {
         }
     });
 
+    grunt.loadTasks('tasks/');
+
     var plugins = [
         'grunt-contrib-clean',
         'grunt-contrib-compress',
@@ -135,6 +155,7 @@ module.exports = function(grunt) {
         'copy:publish',
         'compress:publish',
         'nugetpack:publish',
+        'check-bom:publish',
     ]);
 
     grunt.registerTask('finished-publish', function (mode) {

tasks/check-bom.js

@@ -0,0 +1,26 @@
+// Copyright (c) Microsoft Corporation.  All Rights Reserved. Licensed under the MIT License. See License.txt in the project root for license information.
+(function () {
+    "use strict";
+
+    module.exports = function (grunt) {
+
+        // Verifies that files begin with a UTF8 BOM. Files without one will not be able to pass the
+        // Windows App Certification Kit test.
+
+        grunt.registerMultiTask("check-bom", function () {
+            function checkBom(filePath) {
+                if (grunt.file.exists(filePath)) {
+                    var content = grunt.file.read(filePath, { encoding: null });
+                    if (content.length < 3 || content[0] !== 0xef || content[1] !== 0xbb || content[2] !== 0xbf) {
+                        grunt.fail.fatal("check-bom File is missing BOM: " + filePath);
+                    }
+                } else {
+                    grunt.log.warn("check-bom No such file: " + filePath);
+                }
+            }
+
+            this.filesSrc.forEach(checkBom);
+        });
+
+    };
+})();