Add support for sourcemap

lib/index.js

@@ -3,13 +3,21 @@ 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
+
+module.exports = function(contents, sourcemap) {
   const id = genId(this.resourcePath)
   let hasComponent = false
 
-  const ast = acorn.parse(contents, {
-    sourceType: 'module'
-  })
+  const parseOptions = { sourceType: 'module' }
+
+  if (this.sourceMap) {
+    parseOptions.locations = true
+    parseOptions.sourceFile = this.resourcePath
+  }
+
+  const ast = acorn.parse(contents, parseOptions)
 
   const res = estraverse.replace(ast, {
     enter (node, parent) {
@@ -39,8 +47,34 @@ module.exports = function(contents) {
     }
   })
 
-  return genCode.generate(res)
-    + (hasComponent ? genHotReload(id) : '')
+  if (!hasComponent) {
+    this.callback(null, contents, sourcemap)
+    return
+  }
+
+  if (this.sourceMap) {
+    const generatedContents = genCode.generate(res, {
+      sourceMap: this.resourcePath,
+      sourceMapWithCode: true,
+      sourceContent: contents
+    })
+
+    // apply the original sourcemap to the sourcemap generated by escodegen.
+    const sourceMapGenerator = generatedContents.map
+
+    if (sourcemap) {
+      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))
+  }
 }
 
 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())
   })
 }