Still getting 'address already in use' using --inspect on typescript projects

Bug report

When using NODE_OPTIONS='--inspect' next dev -p 1337 I’m still getting the error: Starting inspector on 127.0.0.1:9229 failed: address already in use

Describe the bug

From what I understand, this bug should have been fixed as of https://github.com/zeit/next.js/pull/11041.

However, I still get the error:

npm run dev

> frontend@0.1.0 dev 
> NODE_OPTIONS='--inspect' next dev -p 1337

Debugger listening on ws://127.0.0.1:9229/90c3d543-273f-492c-a8f6-bb3afd978e64
For help, see: https://nodejs.org/en/docs/inspector
[ wait ]  starting the development server ...
[ info ]  waiting on http://localhost:1337 ...

Starting inspector on 127.0.0.1:9229 failed: address already in use

To Reproduce

Steps to reproduce the behavior, please provide code snippets or a repository:

1. Edit package.json’s dev script:

 "scripts": {
    "dev": "NODE_OPTIONS='--inspect' next dev -p 1337",
    ...
  },
  "dependencies": {
    "next": "9.3.4",
    ...
  },

1. npm run dev or yarn dev
2. See error

npm run dev

> frontend@0.1.0 dev 
> NODE_OPTIONS='--inspect' next dev -p 1337

Debugger listening on ws://127.0.0.1:9229/90c3d543-273f-492c-a8f6-bb3afd978e64
For help, see: https://nodejs.org/en/docs/inspector
[ wait ]  starting the development server ...
[ info ]  waiting on http://localhost:1337 ...

Starting inspector on 127.0.0.1:9229 failed: address already in use

Expected behavior

Do not see address already in use error

Screenshots

If applicable, add screenshots to help explain your problem.

System information

• OS: macOS
• Browser (if applies) [e.g. chrome, safari]
• Version of Next.js: 9.3.4 (also tried on 9.3.5-canary.7)
• Version of Node.js: 12.16.2

[Janpot]

The conflicting port comes from fork-ts-checker-webpack-plugin which starts its childprocess with the same environment variables as the host process. I opened https://github.com/TypeStrong/fork-ts-checker-webpack-plugin/pull/405 to get around this. You can also use

NODE_OPTIONS='--inspect=0'

to assign a random port. You’ll have to manually configure devtools with this port afterwards though.

edit:

Looks like fork-ts-checker-webpack-plugin isn’t used during next dev anymore, so this shouldn’t be a problem anymore

[PeoB]

Had same issue, tried with 9.3.4 and 9.3.5-canary.7.

Ended up simply doing node --inspect node_modules/next/dist/bin/next dev which seems to do the trick for me