Add support for sourcemap

Close ktsn#4

lib/index.js

@@ -3,12 +3,18 @@ const estraverse = require('estraverse')
 const genCode = require('escodegen')
 const genId = require('./gen-id')
 
-module.exports = function(contents) {
+var sourceMap = require('source-map');
+var SourceMapConsumer = sourceMap.SourceMapConsumer;
+var SourceMapGenerator = sourceMap.SourceMapGenerator;
+
+module.exports = function(contents, sourcemap) {
   const id = genId(this.resourcePath)
   let hasComponent = false
 
   const ast = acorn.parse(contents, {
-    sourceType: 'module'
+    sourceType: 'module',
+    locations: true,
+    sourceFile: this.resourcePath
   })
 
   const res = estraverse.replace(ast, {
@@ -39,8 +45,30 @@ module.exports = function(contents) {
     }
   })
 
-  return genCode.generate(res)
-    + (hasComponent ? genHotReload(id) : '')
+  if (hasComponent) {
+    if (sourcemap) {
+      let generatedContents = genCode.generate(res, {
+        sourceMap: this.resourcePath,
+        sourceMapWithCode: true,
+        sourceContent: contents
+      })
+
+      // apply the original sourcemap to the sourcemap generated by escodegen.
+      let sourceMapGenerator = SourceMapGenerator.fromSourceMap(generatedSmc)
+
+      let originalSmc = new SourceMapConsumer(sourcemap)
+      sourceMapGenerator.applySourceMap(originalSmc)
+      let outSourcemap = sourceMapGenerator.toJSON()
+
+      this.callback(null, generatedContents.code + genHotReload(id), outSourcemap)
+    } else {
+      let generatedContents = genCode.generate(res);
+
+      this.callback(null, generatedContents + genHotReload(id))
+    }
+  } else {
+    this.callback(null, contents, sourcemap)
+  }
 }
 
 function genHotReload (id) {