Add support for sourcemap

Close #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) {
+const sourceMap = require('source-map')
+const SourceMapConsumer = sourceMap.SourceMapConsumer
+const 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 +45,31 @@ module.exports = function(contents) {
     }
   })
 
-  return genCode.generate(res)
-    + (hasComponent ? genHotReload(id) : '')
+  if (hasComponent) {
+    if (sourcemap) {
+      const generatedContents = genCode.generate(res, {
+        sourceMap: this.resourcePath,
+        sourceMapWithCode: true,
+        sourceContent: contents
+      })
+
+      // apply the original sourcemap to the sourcemap generated by escodegen.
+      const generatedSmc = generatedContents.map.toJSON()
+      const sourceMapGenerator = SourceMapGenerator.fromSourceMap(generatedSmc)
+
+      const originalSmc = new SourceMapConsumer(sourcemap)
+      sourceMapGenerator.applySourceMap(originalSmc)
+      const outSourcemap = sourceMapGenerator.toJSON()
+
+      this.callback(null, generatedContents.code + genHotReload(id), outSourcemap)
+    } else {
+      const generatedContents = genCode.generate(res)
+
+      this.callback(null, generatedContents + genHotReload(id))
+    }
+  } else {
+    this.callback(null, contents, sourcemap)
+  }
 }
 
 function genHotReload (id) {

test/specs/index.spec.js

@@ -1,13 +1,18 @@
 const path = require('path')
 const fs = require('fs')
-const loader = require('../../lib/index')
+const DefaultLoader = require('../../lib/index')
+
+class Loader extends DefaultLoader {
+  callback(err, contents, sourcemap) { this.callbackAnswer = { err, contents, sourcemap } }
+}
 
 function test (name) {
   const src = fs.readFileSync(path.resolve(__dirname, '../fixtures', name), 'utf8')
   const expected = fs.readFileSync(path.resolve(__dirname, '../expects', name), 'utf8')
 
   it(name, () => {
-    expect(loader(src).replace(/if \(module\.hot\)[\s\S]*$/, '').trim()).toBe(expected.trim())
+    const loader = new Loader(src)
+    expect(loader.callbackAnswer.contents.replace(/if \(module\.hot\)[\s\S]*$/, '').trim()).toBe(expected.trim())
   })
 }