wip: Improvements

.babelrc

@@ -1,5 +1,10 @@
 {
-  "plugins": [
-    "transform-es2015-modules-commonjs"
+  "presets": [
+    [
+      "env",
+      {
+        "node": 4
+      }
+    ]
   ]
 }

__test__/index.test.js

@@ -0,0 +1,80 @@
+/* eslint-env jest */
+import path from 'path'
+import fs from 'fs'
+import del from 'del'
+import webpack from 'webpack'
+import { SourceMapConsumer } from 'source-map'
+import ButternutWebpackPlugin from '../index'
+
+const buildDir = path.join(__dirname, 'build')
+
+describe('butternut-webpack-plugin', () => {
+  afterEach(() =>
+    del(buildDir)
+  )
+
+  describe('sourcemaps', () => {
+    beforeEach(() =>
+      run({
+        devtool: 'sourcemap',
+      })
+    )
+
+    test('should have sourcemaps with correct filenames', async () => {
+      const src = await sources()
+      const srcWithouthWebpackPrefix = src.map(removeWebpackPrefix)
+      expect(srcWithouthWebpackPrefix).toContain('__test__/resources/a.js')
+      expect(srcWithouthWebpackPrefix).toContain('__test__/resources/b.js')
+      expect(srcWithouthWebpackPrefix).toContain('__test__/resources/app.js')
+    })
+  })
+})
+
+function run (webpackConfigOpts, butternutOpts) {
+  const compiler = webpack(getConfig(webpackConfigOpts, butternutOpts))
+  return new Promise((resolve, reject) => {
+    compiler.run((err, stats) => {
+      if (err) {
+        return reject(err)
+      }
+      return resolve(stats)
+    })
+  })
+}
+
+async function sources () {
+  const fileContent = await getFile('bundle.js.map')
+  const map = JSON.parse(fileContent)
+  const smc = new SourceMapConsumer(map)
+  return smc.sources
+}
+
+function getFile (file) {
+  return new Promise((resolve, reject) => {
+    fs.readFile(path.join(buildDir, file), 'utf-8', (error, data) => {
+      if (error) {
+        return reject(error)
+      }
+
+      return resolve(data)
+    })
+  })
+}
+
+function getConfig (webpackConfigOpts = {}, butternutOpts = {}) {
+  return {
+    entry: path.join(__dirname, 'resources/app.js'),
+    output: {
+      filename: 'bundle.js',
+      path: buildDir,
+    },
+    plugins: [
+      new ButternutWebpackPlugin(butternutOpts),
+    ],
+    devtool: webpackConfigOpts.devtool ? webpackConfigOpts.devtool : undefined,
+  }
+}
+
+function removeWebpackPrefix (s) {
+  return s.replace('webpack:///', '')
+}

__test__/resources/a.js

@@ -0,0 +1 @@
+export default 'a'

__test__/resources/app.js

@@ -0,0 +1,8 @@
+import a from './a'
+import b from './b'
+
+run(a, b)
+
+function run (a, b) {
+  console.log(a + b) // eslint-disable-line no-console
+}

__test__/resources/b.js

@@ -0,0 +1 @@
+export default 'b'

index.js

@@ -1,9 +1,7 @@
 import ModuleFilenameHelpers from 'webpack/lib/ModuleFilenameHelpers'
-import { RawSource } from 'webpack-sources'
+import { RawSource, SourceMapSource } from 'webpack-sources'
 import { squash } from 'butternut'
 
-const isEntryChunk = chunk => chunk.hasRuntime() && chunk.isInitial()
-
 export default class ButternutPlugin {
 
   constructor (conf = {}) {
@@ -12,24 +10,51 @@ export default class ButternutPlugin {
 
   apply (compiler) {
 
+    const useSourceMap = typeof this.conf.sourceMap === 'undefined'
+      ? !!compiler.options.devtool
+      : this.conf.sourceMap
+
     compiler.plugin('compilation', compilation => {
+
+      if (useSourceMap) {
+        compilation.plugin('build-module', module => {
+          module.useSourceMap = true
+        })
+      }
+
       compilation.plugin('optimize-chunk-assets', (chunks, callback) => {
 
-        for (const chunk of chunks) {
-          const files = chunk.files
+        const matchObjectOpts = { test: /\.js($|\?)/i }
+        const files = getFiles(chunks, compilation, matchObjectOpts)
 
-          for (const file of files) {
-            const matchObjectConfiguration = { test: /\.js($|\?)/i }
+        for (const file of files) {
 
-            if (ModuleFilenameHelpers.matchObject(matchObjectConfiguration, file)) {
-              const asset = compilation.assets[file]
-              const code = isEntryChunk(chunk) ? asset.source() : `__assumeDataProperty(global, "webpackJsonp", __abstract("function"))\n ${asset.source()}`
-              const transformed = squash(code, this.conf)
+          if (!ModuleFilenameHelpers.matchObject(matchObjectOpts, file)) {
+            return
+          }
 
-              compilation.assets[file] = new RawSource(transformed.code)
-            }
+          const asset = compilation.assets[file]
 
+          if (asset.__butternutfied) {
+            return
           }
+
+          const { input, inputSourceMap } = getAssetParts(asset, useSourceMap)
+
+          // TODO: We need to find a way to pass `inputSourceMap` to squash(),
+          // so the final output source map will be based on `inputSourceMap`.
+          const transformed = squash(input, {
+            check: this.conf.check,
+            allowDangerousEval: this.conf.allowDangerousEval,
+            sourceMap: useSourceMap,
+          })
+
+          const source = transformed.map
+            ? new SourceMapSource(transformed.code, file, transformed.map, input, inputSourceMap)
+            : new RawSource(transformed.code)
+
+          asset.__butternutfied = compilation.assets[file] = source
+
         }
 
         callback()
@@ -38,3 +63,24 @@ export default class ButternutPlugin {
     })
   }
 }
+
+function getFiles (chunks, compilation) {
+  const files = []
+  chunks.forEach(chunk => files.push(...chunk.files))
+  files.push(...compilation.additionalChunkAssets)
+
+  return files
+}
+
+function getAssetParts (asset, useSourceMap) {
+  if (useSourceMap && asset.sourceAndMap) {
+    const sourceAndMap = asset.sourceAndMap()
+    return { input: sourceAndMap.source, inputSourceMap: sourceAndMap.map }
+  }
+
+  if (useSourceMap) {
+    return { input: asset.source(), inputSourceMap: asset.map() }
+  }
+
+  return { input: asset.source() }
+}

package.json

@@ -7,6 +7,7 @@
     "dist"
   ],
   "scripts": {
+    "test": "jest",
     "build": "rm -rf dist && babel index.js --out-dir dist",
     "lint": "eslint index.js"
   },
@@ -19,9 +20,12 @@
   "devDependencies": {
     "babel-cli": "^6.24.1",
     "babel-eslint": "^7.2.3",
-    "babel-plugin-transform-es2015-modules-commonjs": "^6.24.1",
+    "babel-jest": "^20.0.1",
+    "babel-preset-env": "^1.4.0",
+    "del": "^2.2.2",
     "eslint": "^3.19.0",
     "eslint-config-zavatta": "^4.3.0",
+    "jest": "^20.0.1",
     "webpack": "^2.5.1"
   },
   "repository": {