Cannot set property 'webpackStats' of undefined

[cexoso]

• Operating System: MacOS
• Node Version: v8.4.0
• NPM Version: 5.6.0
• webpack version: 4.1.1
• webpack-dev-middleware Version: 1.12.0

• [*] This is a bug

Code

var webpack = require('webpack')
var path = require('path')
module.exports = {
    name: 'backend dev hot middlware',
    mode: "development",
    entry: [
        'webpack-hot-middleware/client?path=/__webpack_hmr&timeout=20000',
        './src/app/index.js'
    ],
    output: {
        path: path.join(__dirname, '/public/static'),
        filename: '[name].js',
        chunkFilename: '[id].chunk.js',
        publicPath: '/build/'
    },
    resolve: {
        extensions: ['.js', '.jsx']
    },
    module: {
        rules: [
            {
                test: /\.jsx|.js$/,
                loader: 'babel-loader',
                exclude: /node_modules/,
                query: {
                    presets: ['env']
                }
            }
        ]
    }
}

#!/usr/bin/env node
console.log('start babel env ...')
require('babel-polyfill')
require('babel-core/register')
console.log('Waiting for webpacking ...')
var Koa = require('koa')
var app = new Koa();
var { devMiddleware, hotMiddleware } = require('koa-webpack-middleware')
var chokidar = require('chokidar')
var webpack = require('webpack')
var webpackConfig = require('../webpack.config')
var path = require('path')
var { getPortPromise } = require('portfinder')
var applyMiddlewares = require('../src/server/applyMiddlewares').default;
var compiler = webpack(webpackConfig);
app.use(
    devMiddleware(compiler, {
        noInfo: true,
        watchOptions: {
            aggregateTimeout: 300,
            poll: true
        },
        publicPath: '/build/',
        stats: {
            colors: true
        },
        serverSideRender: true 
    })
);
app.use(
    hotMiddleware(compiler, {
        log: console.log,
        path: '/__webpack_hmr',
        heartbeat: 10 * 1000
    })
);
applyMiddlewares(app);
app.use((ctx, next) => {
    const  assetsByChunkName = ctx.res.locals.webpackStats.toJson().assetsByChunkName
    console.log(assetsByChunkName.compilation.Compilation.inputFileSystem)
    // then use `assetsByChunkName` for server-sider rendering
})
app.on('error', function (err, ctx) {
    console.log('error occured:', err.stack)
})

var server = require('http').createServer(app.callback())

var watcher = chokidar.watch([
    path.join(__dirname, '../src/server')
])
watcher.on('ready', function () {
    watcher.on('all', function (e, p) {
        console.log("Clearing module cache");
        Object.keys(require.cache).forEach(function (id) {
            if (/[\/\\](server)[\/\\]/.test(id)) delete require.cache[id];
        });
    })
})
var isListened = false
compiler.plugin("emit", function (compilation, callback) {
    callback()
    if (!isListened) {
        getPortPromise().then(
            port => server.listen(port, function () {
                console.log('App started, at port %d', port)
                isListened = true
            }),
            (err) => {
                console.log('Could not get a free port', err);
                process.exit(-1);
            }
        )
    }
});

Expected Behavior

I want to get assetsByChunkName.

Actual Behavior

error occured: TypeError: Cannot set property 'webpackStats' of undefined
at /Users/xiongjie/Documents/GitHub/react_isomorphism/node_modules/webpack-dev-middleware/middleware.js:30:30
at Object.ready (/Users/xiongjie/Documents/GitHub/react_isomorphism/node_modules/webpack-dev-middleware/lib/Shared.js:166:29)
at /Users/xiongjie/Documents/GitHub/react_isomorphism/node_modules/webpack-dev-middleware/middleware.js:29:12
at Promise ()
at goNext (/Users/xiongjie/Documents/GitHub/react_isomorphism/node_modules/webpack-dev-middleware/middleware.js:28:11)
at webpackDevMiddleware (/Users/xiongjie/Documents/GitHub/react_isomorphism/node_modules/webpack-dev-middleware/middleware.js:41:33)
at _callee$ (/Users/xiongjie/Documents/GitHub/react_isomorphism/node_modules/koa-webpack-middleware/lib/devMiddleware.js:23:22)
at tryCatch (/Users/xiongjie/Documents/GitHub/react_isomorphism/node_modules/regenerator-runtime/runtime.js:65:40)
at Generator.invoke [as _invoke] (/Users/xiongjie/Documents/GitHub/react_isomorphism/node_modules/regenerator-runtime/runtime.js:303:22)
at Generator.prototype.(anonymous function) [as next] (/Users/xiongjie/Documents/GitHub/react_isomorphism/node_modules/regenerator-runtime/runtime.js:117:21)

[shellscape]

You'll need to provide a repo that we'll be able to reproduce this one.