feat: adding sourcemap support

index.js

@@ -1,19 +1,38 @@
 'use strict';
 
+var SourceMapConsumer = require('source-map').SourceMapConsumer;
 var isparta = require('isparta');
 
-module.exports = function(source) {
+module.exports = function(source, map) {
     var config = this.options.isparta || {
         embedSource: true,
         noAutoWrap: true,
         babel: this.options.babel
     };
 
+    if(this.sourceMap){
+      config.codeGenerationOptions = config.codeGenerationOptions || {};
+      config.codeGenerationOptions.sourceMap = this.resourcePath;
+      config.codeGenerationOptions.sourceMapWithCode = true;
+    }
+
     var instrumenter = new isparta.Instrumenter(config);
 
     if (this.cacheable) {
         this.cacheable();
     }
 
-    return instrumenter.instrumentSync(source, this.resourcePath);
+    var instrumented = instrumenter.instrumentSync(source, this.resourcePath);
+
+    if(this.sourceMap){
+      var outMap = instrumenter.lastSourceMap();
+
+      if(outMap){
+          outMap.applySourceMap(new SourceMapConsumer(map), this.resourcePath);
+
+          map = outMap.toJSON();
+      }
+    }
+
+    this.callback(null, instrumented, map);
 };

package.json

@@ -9,7 +9,8 @@
   "main": "index.js",
   "files": [ "index.js" ],
   "dependencies": {
-    "isparta": "4.x.x"
+    "isparta": "4.x.x",
+    "source-map": "^0.5.6"
   },
   "engines": {
     "node": ">=0.10.0"