Next.js: TypeError: Cannot read property 'map' of undefined at Server.generateRoutes

Created on 6 Jan 2020  路  17Comments  路  Source: vercel/next.js

Bug report

Describe the bug

I've been using nextjs with typescript to build a web app (based off of the example at https://github.com/mui-org/material-ui/tree/master/examples/nextjs-with-typescript). However, when I deploy my app to an AWS elastic beanstalk instance, I get a strange error that breaks my app. next start does not run correctly. I cannot reproduce this locally, only when I deploy to AWS's elastic beanstalk.

Stack trace:

> next start --port 8081

TypeError: Cannot read property 'map' of undefined
    at Server.generateRoutes (/var/app/current/node_modules/next/dist/next-server/server/next-server.js:257:36)
    at new Server (/var/app/current/node_modules/next/dist/next-server/server/next-server.js:81:49)
    at createServer (/var/app/current/node_modules/next/dist/server/next.js:2:133)
    at start (/var/app/current/node_modules/next/dist/server/lib/start-server.js:1:323)
    at nextStart (/var/app/current/node_modules/next/dist/cli/next-start.js:22:125)
    at commands.(anonymous function).then.exec (/var/app/current/node_modules/next/dist/bin/next:29:346)
    at process._tickCallback (internal/process/next_tick.js:68:7)
    at Function.Module.runMain (internal/modules/cjs/loader.js:834:11)
    at startup (internal/bootstrap/node.js:283:19)
    at bootstrapNodeJSCore (internal/bootstrap/node.js:623:3)
npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! [email protected] start: `next start --port 8081`
npm ERR! Exit status 1
npm ERR! 
npm ERR! Failed at the [email protected] start script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.

To Reproduce

Deploy nextjs app with typescript to elastic beanstalk instance

Expected behavior

The app should just run next start normally.

System information

  • OS: Node.js running on 64bit Amazon Linux/4.12.0
  • Version of Next.js: both 9.1.16 and 9.1.17
please add a complete reproduction
Source
picture raguiar2

Most helpful comment

I was able to fix the issue simply with
rm -rf .next (i.e. clearing the "cached" files) and then building anew with npm run build

I will say one thing however, there's a lot of issues I've been having with next.js and whenever I find the bug posted here the development team always seem to deny any issues.

In this case, it's not really a bug with next.js, but perhaps advising to clear the cache and rebuild would be more constructive than "Cannot reproduce. Next.js can do no wrong."

picture modamodamoda on 24 Jan 2020
👍5

All 17 comments

Same error happen.
This error may only happen if we start up server with custom server.
https://nextjs.org/docs/advanced-features/custom-server

Temporary I've resolve the issue by decrease next.js version to 9.1.14

takashi-yokomichi picture takashi-yokomichi on 7 Jan 2020
👍2

This error occued in next.js 9.1.6 too.

mogaming217 picture mogaming217 on 7 Jan 2020

A full reproduction is needed.

timneutkens picture timneutkens on 7 Jan 2020

Facing this issue as well and downgraded to 9.1.4

adamthewan picture adamthewan on 10 Jan 2020

@adamthewan please provide a full reproduction otherwise your comment really is not helpful in resolving the issue.

timneutkens picture timneutkens on 10 Jan 2020

Yup sorry about that.

My build environment is inside Google Cloud Functions

System information

OS: Node.js 10 (Beta)
Version of Next.js: 9.1.7

My build is something like this:

const next = require('next');
const path = require('path');

exports.app = functions.https.onRequest(async (req, res) => {
  const nextApp = next({
    dev: false,
    conf: {
      distDir: `${path.relative(process.cwd(), __dirname)}/dist/prod/.next`,
    },
  });

    await nextApp.prepare();
    const handle = nextApp.getRequestHandler();
    handle(req, res);

});

Describe the bug

When accessing the endpoint, the server will crash with this log:

TypeError: Cannot read property 'map' of undefined
    at Server.generateRoutes (/srv/functions/node_modules/next/dist/next-server/server/next-server.js:257:36)
    at new Server (/srv/functions/node_modules/next/dist/next-server/server/next-server.js:81:49)
    at createServer (/srv/functions/node_modules/next/dist/server/next.js:2:133)
    at exports.app.functions.https.onRequest (/srv/functions/index.js:12:19)
    at cloudFunction (/srv/functions/node_modules/firebase-functions/lib/providers/https.js:49:9)
    at process.nextTick (/srv/node_modules/@google-cloud/functions-framework/build/src/invoker.js:243:17)
    at process._tickCallback (internal/process/next_tick.js:61:11)
adamthewan picture adamthewan on 10 Jan 2020

I'm going to post the exact same reply. This time with bold text.

Please provide a full reproduction otherwise the comment really is not helpful in resolving the issue.

timneutkens picture timneutkens on 10 Jan 2020
👎1

facing the same issue

vaibhav269 picture vaibhav269 on 14 Jan 2020

@vaibhav269 this is really not helpful in resolving the issue. As said:

Please provide a full reproduction otherwise the comment really is not helpful in resolving the issue.

timneutkens picture timneutkens on 14 Jan 2020

This is the package.json file

{
  "name": "darecase",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "dependencies": {
    "@fortawesome/fontawesome-svg-core": "^1.2.26",
    "@fortawesome/free-solid-svg-icons": "^5.12.0",
    "@fortawesome/react-fontawesome": "^0.1.8",
    "cookie-parser": "^1.4.4",
    "express": "^4.17.1",
    "isomorphic-unfetch": "^3.0.0",
    "js-cookie": "^2.2.1",
    "mysql": "^2.17.1",
    "next": "9.1.4",
    "rand-token": "^0.4.0",
    "react": "^16.12.0",
    "react-dom": "^16.12.0"
  },
  "devDependencies": {
    "styled-jsx": "^3.2.4"
  },
  "scripts": {
    "dev": "nodemon index.js",
    "build": "next build",
    "start": "NODE_ENV=production node index.js"
  },
  "keywords": [],
  "author": "",
  "license": "ISC"
}

The server file is 

const next = require('next');
const express = require('express');
const uid = require('rand-token').uid;
const dev = process.env.NODE_ENV !== 'production';
const port = process.env.port || 3000;
const con = require('./config/db');
const cookieParser = require('cookie-parser');

const app = next({dev});
const handle = app.getRequestHandler();

app.prepare().then(()=>{
    const server = express();
    server.use(express.json());

    server.use(cookieParser());

    server.get('*',(req,res)=>{
        return handle(req,res);
    });

    server.listen(port,err=>{
        if(err){
            throw err;
        }else{
            console.log("server running at port",port);
        }
    })
})

Everything works fine in local server but when i try to host the application to the server in production mode i get this error on running 'npm run start'
Note: The application works fine in the development mode too... I am facing the error only in the case of production mode.

TypeError: Cannot read property 'map' of undefined
    at Server.generateRoutes (/var/app/current/node_modules/next/dist/next-server/server/next-server.js:257:36)
    at new Server (/var/app/current/node_modules/next/dist/next-server/server/next-server.js:81:49)
    at createServer (/var/app/current/node_modules/next/dist/server/next.js:2:133)
    at start (/var/app/current/node_modules/next/dist/server/lib/start-server.js:1:323)
    at nextStart (/var/app/current/node_modules/next/dist/cli/next-start.js:22:125)
    at commands.(anonymous function).then.exec (/var/app/current/node_modules/next/dist/bin/next:29:346)
    at process._tickCallback (internal/process/next_tick.js:68:7)
    at Function.Module.runMain (internal/modules/cjs/loader.js:834:11)
    at startup (internal/bootstrap/node.js:283:19)
    at bootstrapNodeJSCore (internal/bootstrap/node.js:623:3)
npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! [email protected] start: `next start --port 8081`
npm ERR! Exit status 1
npm ERR! 
npm ERR! Failed at the [email protected] start script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.

Fixed the issue by sticking to the version v9.4.1 i.e by removing the '^' in "next": "^9.1.4" in package.json

Hope that helps :)

vaibhav269 picture vaibhav269 on 14 Jan 2020

Please provide a full reproduction including all code. Just 2 files is not enough.

timneutkens picture timneutkens on 14 Jan 2020
👎8

Sorry but i can't reveal the full code. Try it out according to me given files are enough to reproduce the error.

  1. Run 'npm install'
  2. Run 'npm run build'
  3. Host the application to a server
  4. Run 'npm run start'

You will probably get the error

vaibhav269 picture vaibhav269 on 14 Jan 2020

@vaibhav269 Just tried it with the provided files and steps and I could not reproduce.

timneutkens picture timneutkens on 15 Jan 2020

I was able to fix the issue simply with
rm -rf .next (i.e. clearing the "cached" files) and then building anew with npm run build

I will say one thing however, there's a lot of issues I've been having with next.js and whenever I find the bug posted here the development team always seem to deny any issues.

In this case, it's not really a bug with next.js, but perhaps advising to clear the cache and rebuild would be more constructive than "Cannot reproduce. Next.js can do no wrong."

modamodamoda picture modamodamoda on 24 Jan 2020
👍5

I will say one thing however, there's a lot of issues I've been having with next.js and whenever I find the bug posted here the development team always seem to deny any issues.

We don't deny issues. I've already spent over an hour on this particular issue without being able to reproduce as no reproduction was provided.

We ask for a reproduction so that we can add a test in our test suite to ensure it doesn't happen again.

Eg in this case I've asked for a full reproduction 5 times and 1 time it was provided, tried to reproduce based on the steps provided and couldn't reproduce so posted back. Didn't hear back from anyone experiencing the issue since.

In this case, it's not really a bug with next.js, but perhaps advising to clear the cache and rebuild would be more constructive than "Cannot reproduce. Next.js can do no wrong."

Specifically "Next.js can do no wrong"

I've never said that, I've only asked for a reproduction so that we can actually solve the issue you're experiencing.

timneutkens picture timneutkens on 24 Jan 2020
👎3 👍2

Sorry, jump to this.
I faced this same error.
in pages/index.js, I used .map to looping fetch API response and build to Netlify.
When I deploy it, I got this error.
Screenshot below:
http://prnt.sc/tlunq7

barayuda picture barayuda on 21 Jul 2020

Sorry, jump to this.
I faced this same error.
in pages/index.js, I used .map to looping fetch API response and build to Netlify.
When I deploy it, I got this error.
Screenshot below:
http://prnt.sc/tlunq7

I'm facing the same issue on Vercel. I'm trying to map over an array in getStaticPaths and it throws the same error.

manuarora700 picture manuarora700 on 2 Nov 2020
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