当尝试从Babel 6升级到Babel 7时，webpack模块构建失败

Question

我正尝试将我们的项目从Babel 6升级到7。我已经对package.json进行了以下更改：

  "devDependencies": {
    "babel-core": "6.26.3",
    "babel-eslint": "10.0.1",
    "babel-loader": "7.1.5",
    "babel-plugin-syntax-dynamic-import": "6.18.0",
    "babel-plugin-transform-class-properties": "6.24.1",
    "babel-plugin-transform-es2015-destructuring": "6.23.0",
    "babel-polyfill": "6.26.0",
    "babel-preset-env": "1.7.0",
    "babel-preset-es2015": "6.24.1",
    "babel-preset-react": "6.24.1",
    "webpack": "4.28.4",
    "webpack-bundle-analyzer": "3.1.0",
    "webpack-cli": "3.2.1",
    "webpack-dev-server": "3.1.14",
    "workbox-webpack-plugin": "3.6.3"
  },

移除了babel-preset-*并新增了新的@babel/*包。同时，还添加了Jest。

  "devDependencies": {
    "@babel/cli": "7.2.3",
    "@babel/core": "7.3.4",
    "@babel/preset-env": "7.3.4",
    "@babel/preset-react": "7.0.0",
    "babel-eslint": "10.0.1",
    "babel-loader": "8.0.5",
    "babel-plugin-syntax-dynamic-import": "6.18.0",
    "babel-plugin-transform-class-properties": "6.24.1",
    "babel-plugin-transform-es2015-destructuring": "6.23.0",
    "babel-polyfill": "6.26.0",
    "jest": "24.3.0",
    "react-test-renderer": "16.8.4",
    "webpack": "4.28.4",
    "webpack-bundle-analyzer": "3.1.0",
    "webpack-cli": "3.2.1",
    "webpack-dev-server": "3.1.14",
    "workbox-webpack-plugin": "3.6.3"
  },

我们的项目使用 Babel 和 Webpack，并通过 webpack.config.js 管理 Babel 配置。因此，在该文件中进行了以下更改：

webpack.config.js

  module: {
    rules: [
      {
        enforce: 'pre',
        test: /\.js$/,
        exclude: /node_modules/,
        loader: 'eslint-loader'
      },
      {
        test: /\.js$/,
        exclude: /node_modules/,
        loader: 'babel-loader',
        query: {
          presets: ['react', 'es2015', 'env'],
          plugins: ['transform-class-properties', 'syntax-dynamic-import', 'transform-es2015-destructuring', 'transform-object-rest-spread']
        }
      },
    ]
  }

更新预设部分，使用@babel/react 和 @babel/env.

  module: {
    rules: [
      {
        enforce: 'pre',
        test: /\.js$/,
        exclude: /node_modules/,
        loader: 'eslint-loader'
      },
      {
        test: /\.jsx?$/,
        exclude: /node_modules/,
        loader: 'babel-loader',
        query: {
          presets: ['@babel/react', '@babel/env'],
          plugins: ['transform-class-properties', 'syntax-dynamic-import', 'transform-es2015-destructuring', 'transform-object-rest-spread']
        }
      },
    ]
  }

当我运行 webpack --mode development 时，webpack 抛出以下错误：

ERROR in ./src/entry2.js
Module build failed (from ./node_modules/babel-loader/lib/index.js):
Error: Cannot find module 'babel-preset-react' from 'C:\MyApp'
- If you want to resolve "react", use "module:react"
- Did you mean "@babel/react"?
    at Function.module.exports [as sync] (C:\MyApp\node_modules\resolve\lib\sync.js:58:15)
    at resolveStandardizedName (C:\MyApp\node_modules\@babel\core\lib\config\files\plugins.js:101:31)
    at resolvePreset (C:\MyApp\node_modules\@babel\core\lib\config\files\plugins.js:58:10)
    at loadPreset (C:\MyApp\node_modules\@babel\core\lib\config\files\plugins.js:77:20)
    at createDescriptor (C:\MyApp\node_modules\@babel\core\lib\config\config-descriptors.js:154:9)
    at items.map (C:\MyApp\node_modules\@babel\core\lib\config\config-descriptors.js:109:50)
    at Array.map (<anonymous>)
    at createDescriptors (C:\MyApp\node_modules\@babel\core\lib\config\config-descriptors.js:109:29)
    at createPresetDescriptors (C:\MyApp\node_modules\@babel\core\lib\config\config-descriptors.js:101:10)
    at presets (C:\MyApp\node_modules\@babel\core\lib\config\config-descriptors.js:47:19)
    at mergeChainOpts (C:\MyApp\node_modules\@babel\core\lib\config\config-chain.js:320:26)
    at C:\MyApp\node_modules\@babel\core\lib\config\config-chain.js:283:7
    at buildRootChain (C:\MyApp\node_modules\@babel\core\lib\config\config-chain.js:120:22)
    at loadPrivatePartialConfig (C:\MyApp\node_modules\@babel\core\lib\config\partial.js:85:55)
    at Object.loadPartialConfig (C:\MyApp\node_modules\@babel\core\lib\config\partial.js:110:18)
    at Object.<anonymous> (C:\MyApp\node_modules\babel-loader\lib\index.js:140:26)
    at Generator.next (<anonymous>)
    at asyncGeneratorStep (C:\MyApp\node_modules\babel-loader\lib\index.js:3:103)
    at _next (C:\MyApp\node_modules\babel-loader\lib\index.js:5:194)
    at C:\MyApp\node_modules\babel-loader\lib\index.js:5:364
    at new Promise (<anonymous>)
    at Object.<anonymous> (C:\MyApp\node_modules\babel-loader\lib\index.js:5:97)
    at Object.loader (C:\MyApp\node_modules\babel-loader\lib\index.js:56:18)
    at Object.<anonymous> (C:\MyApp\node_modules\babel-loader\lib\index.js:51:12)

我不明白为什么webpack要查找babel-preset-react模块，当我已经更新了babel-loader的预设部分来使用@babel/react。它甚至会问"是否意味着@babel/react"？是的，这正是我所说的！有什么想法吗？

我在node_modules目录中使用grep搜索了babel-preset-react的引用，并得到了几个结果，来自于我们依赖项中的包（不是devDependencies）。但是，我认为npm install应该可以满足这些包的依赖关系。我错了吗？

最后，第四行提到使用"module:react"是在谈论什么？这与这里有关吗？

- stackleit

---

不确定这是否有太大帮助，但看起来你正在同一个应用程序中混合使用babel 6模块和babel 7模块。您可能需要更新以使用babel模块的@版本，例如@babel/preset-react https://babeljs.io/docs/en/babel-preset-react。此外，有一个工具可以帮助升级到babel 7-https://github.com/babel/babel-upgrade - soundslikeodd

@soundslikeodd，感谢你提供的升级工具链接。它帮助我排除了一些可能性。 - stackleit

Answer 1

我在使用升级工具时遇到了类似的问题，但是解决方法是在我的webpack配置中，该工具没有检测到必要的语法更改...

- hallmanitor

Answer 2

正如评论中所提到的，我之前并不知道有升级工具。使用它帮助我消除了一些我试图手动进行升级时在package.json中引入的错误。

然而，错误仍然存在。但是，在应用升级工具建议的更改后，我看到（并移除）了以下不必要的部分：

  "babel": {
    "presets": [
      "env",
      "react"
    ]
  }

这个部分是导致我的编译错误的原因。显然，我们能够在 webpack 的配置选项旁边运行数月，并且（在幸福的无知中）没有遇到任何问题。在我删除它之后，一切都很好地构建了，使用 Babel 7，仅依赖于 webpack 配置。

如果有一个工具可以帮助优化项目中使用 webpack 和 Babel 的配置（即识别冗余/冲突），那将是很好的。在 .babelrc、package.json 和 webpack.config.js 之间，目前存在着太多的潜在陷阱。

再次感谢您的帮助！

- stackleit