feat(Grunt): add source maps to all min files

lib/grunt/utils.js

@@ -112,27 +112,44 @@ module.exports = {
   },
 
 
-  singleStrict: function(src, insert, newline){
-    var useStrict = newline ? "$1\n'use strict';" : "$1'use strict';";
+  singleStrict: function(src, insert){
     return src
       .replace(/\s*("|')use strict("|');\s*/g, insert) // remove all file-specific strict mode flags
-      .replace(/(\(function\([^)]*\)\s*\{)/, useStrict); // add single strict mode flag
+      .replace(/(\(function\([^)]*\)\s*\{)/, "$1'use strict';"); // add single strict mode flag
+  },
+
+
+  sourceMap: function(mapFile, fileContents) {
+    // use the following once Chrome beta or stable supports the //# pragma
+    // var sourceMapLine = '//# sourceMappingURL=' + mapFile + '\n';
+    var sourceMapLine = '/*\n//@ sourceMappingURL=' + mapFile + '\n*/\n';
+    return fileContents + sourceMapLine;
   },
 
 
   min: function(file, done) {
     var minFile = file.replace(/\.js$/, '.min.js');
+    var mapFile = minFile + '.map';
+    var mapFileName = mapFile.match(/[^\/]+$/)[0];
     shell.exec(
         'java ' +
             this.java32flags() + ' ' +
             '-jar components/closure-compiler/compiler.jar ' +
             '--compilation_level SIMPLE_OPTIMIZATIONS ' +
             '--language_in ECMASCRIPT5_STRICT ' +
+            '--source_map_format=V3 ' +
+            '--create_source_map ' + mapFile + ' ' +
             '--js ' + file + ' ' +
             '--js_output_file ' + minFile,
       function(code) {
         if (code !== 0) grunt.fail.warn('Error minifying ' + file);
-        grunt.file.write(minFile, this.singleStrict(grunt.file.read(minFile), '\n'));
+
+        // closure creates the source map relative to build/ folder, we need to strip those references
+        grunt.file.write(mapFile, grunt.file.read(mapFile).replace('"file":"build/', '"file":"').
+                                                           replace('"sources":["build/','"sources":["'));
+
+        // move add use strict into the closure + add source map pragma
+        grunt.file.write(minFile, this.sourceMap(mapFileName, this.singleStrict(grunt.file.read(minFile), '\n')));
         grunt.log.ok(file + ' minified into ' + minFile);
         done();
     }.bind(this));