Webpack + Express + EJS：错误：找不到模块“。”

Question

我正在使用 webpack、typescript 和 ejs 编写一个 express web 应用程序。当点击应该为 .ejs 文件提供服务的路线之一时，我收到以下错误：

Error: Cannot find module "."
   at webpackMissingModule (/Users/max/Development/test/express-webpack/dist/server.js:20669:74)
   at new View (/Users/max/Development/test/express-webpack/dist/server.js:20669:152)
   at EventEmitter.render (/Users/max/Development/test/express-webpack/dist/server.js:18776:12)
   at ServerResponse.render (/Users/max/Development/test/express-webpack/dist/server.js:20479:7)
   at /Users/max/Development/test/express-webpack/dist/server.js:25508:7
   at Layer.handle [as handle_request] (/Users/max/Development/test/express-webpack/dist/server.js:4524:5)
   at next (/Users/max/Development/test/express-webpack/dist/server.js:4743:13)
   at Route.dispatch (/Users/max/Development/test/express-webpack/dist/server.js:4724:3)
   at Layer.handle [as handle_request] (/Users/max/Development/test/express-webpack/dist/server.js:4524:5)
   at /Users/max/Development/test/express-webpack/dist/server.js:4054:22

代码如下：

package.json:

{
  "name": "express-webpack",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "",
  "license": "ISC",
  "dependencies": {
    "awesome-typescript-loader": "^3.0.0-beta.18",
    "copy-webpack-plugin": "^4.0.1",
    "debug": "^2.6.0",
    "ejs": "^2.5.5",
    "express": "^4.14.0",
    "json-loader": "^0.5.4",
    "source-map-loader": "^0.1.6",
    "webpack": "^2.2.0-rc.3"
  }
}

webpack.config.js

var CopyWebpackPlugin = require('copy-webpack-plugin');

module.exports = {
    entry: __dirname + "/src/index.js",
    target: "node",
    output: {
        filename: "server.js",
        path: __dirname + "/dist"
    },

    // Enable sourcemaps for debugging webpack's output.
    devtool: "source-map",

    resolve: {
        // Add '.ts' and '.tsx' as resolvable extensions.
        extensions: [".webpack.js", ".web.js", ".ts", ".tsx", ".js"]
    },

    module: {
        rules: [
            // All files with a '.ts' or '.tsx' extension will be handled by 'awesome-typescript-loader'.
            { test: /\.tsx?$/, loader: "awesome-typescript-loader" },
            { test: /\.json$/, loader: 'json-loader' },

            // All output '.js' files will have any sourcemaps re-processed by 'source-map-loader'.
            { enforce: "pre", test: /\.js$/, loader: "source-map-loader" }
        ]
    },

    plugins: [
        new CopyWebpackPlugin([
            { from: 'src/views', to: 'views' }
        ])
    ],

    node: {
      fs: "empty"
    }
};

src/index.js

var express = require('express');

var app = express();
app.set("view engine", "ejs");
app.set("views", "./views");
app.get('/', function(req, res, next){
  res.render('index'); // <-- error originates here AFAIK
});
app.listen(8000);

views/index.ejs

hello world

复制步骤：

• 运行webpack 构建项目
• 用node dist/server.js启动服务器
• 访问http://localhost:8000
• 希望看到 index.ejs 的内容，而不是在堆栈跟踪之上

知道出了什么问题吗？

Answer 1

我深入研究了 webpack 生成的代码，发现 webpack 的 context parse evaluation 似乎有一个错误。有一个 express 用于要求选择的视图引擎的简单表达式，但它无法解决这个问题。

为了克服这个问题，你可以在索引中写

const ejs = require("ejs").__express;
const app = express();
app.set("view engine", "ejs");   
app.engine('ejs', ejs);// <-- this does the trick

但如果你想要一个明确的解决方案，请在 webpack repo 上打开一个问题。

Answer 2

我相信您的问题与您的捆绑文件 (dist/server.js) 无权访问您的依赖项、express、模板引擎等。为了 整理一下，您可以配置 webpack 以避免捆绑依赖项 （由于您的应用程序是从服务器/节点端运行的）：

var CopyWebpackPlugin = require('copy-webpack-plugin');

module.exports = {
    entry: __dirname + "/src/index.js",
    target: "node",
    output: {
        filename: "server.js",
        path: __dirname + "/dist"a
    },

    // Enable sourcemaps for debugging webpack's output.
    devtool: "source-map",

    resolve: {
        // Add '.ts' and '.tsx' as resolvable extensions.
        extensions: [".webpack.js", ".web.js", ".ts", ".tsx", ".js"]
    },

    module: {
        rules: [
            // All files with a '.ts' or '.tsx' extension will be handled by 'awesome-typescript-loader'.
            { test: /\.tsx?$/, loader: "awesome-typescript-loader" },
            { test: /\.json$/, loader: 'json-loader' },

            // All output '.js' files will have any sourcemaps re-processed by 'source-map-loader'.
            { enforce: "pre", test: /\.js$/, loader: "source-map-loader" }
        ]
    },

    plugins: [
        new CopyWebpackPlugin([
            { from: 'src/views', to: 'views' }
        ])
    ],

    node: {
      fs: "empty"
    }
};

// Node module dependencies should not be bundled
config.externals = fs.readdirSync("node_modules")
.reduce(function(acc, mod) {
   if (mod === ".bin") {
   return acc
 }

   acc[mod] = "commonjs " + mod
   return acc
}

您可能还需要使用节点选项 config 覆盖节点全局配置 要使视图文件夹可以从您的捆绑文件中访问，更多详细信息： https://webpack.js.org/configuration/node/#components/sidebar/sidebar.jsx

该配置也可以帮助您https://gist.github.com/madx/53853c3d7b527744917f

Answer 3

加上克莱顿的回答，你现在必须在调用 app.engine(string, callback) 时有一个回调函数

app.set('views', 'src/views');
app.set('view engine', 'ejs');
app.engine('ejs', require('ejs').__express); //<-- this