jest-dev-server port detection is not working

[lfdebrux]

🐛 Bug Report

I think (unless I've misconfigured something) that with the latest version of jest if you have a process running already on the server port then the port detection won't happen, and tests and jest-dev-server will try to continue anyway.

To Reproduce

Steps to reproduce the behavior:

1. Start a HTTP server listening on port 3000, for instance with npx http-server -p 3000
2. With the test project (or any project using jest 27.4.3 and jest-dev-server) run npx jest
3. An error from the server command will be output to the terminal with an EADDRINUSE error

Expected behavior

In the past jest-dev-server has prompted the user whether they want to kill the existing process.

Link to repl or repo (highly encouraged)

Repo with minimal example:

https://github.com/lfdebrux/test-jest-dev-server

Run npx envinfo --system --binaries --npmPackages expect-puppeteer,jest-dev-server,jest-environment-puppeteer,jest-puppeteer,spawnd --markdown --clipboard

Paste the results here:

*** Clipboard option removed - use clipboardy or clipboard-cli directly ***


## System:
 - OS: macOS 11.6.1
 - CPU: (8) x64 Intel(R) Core(TM) i7-4770HQ CPU @ 2.20GHz
 - Memory: 86.04 MB / 16.00 GB
 - Shell: 5.1.8 - /usr/local/bin/bash
## Binaries:
 - Node: 16.13.1 - ~/.nvm/versions/node/v16.13.1/bin/node
 - npm: 8.1.2 - ~/.nvm/versions/node/v16.13.1/bin/npm
## npmPackages:
 - jest-dev-server: ^6.0.2 => 6.0.2 

[lfdebrux]

I've tested the minimal example with [email protected] and [email protected] and it fails then too :(

[lfdebrux]

I also can't get the expected behaviour with [email protected] or [email protected] (with [email protected]). Can't get the expected behaviour with [email protected] and jest@26 either, which I'm sure I've seen working before. Maybe it's something in a sub-dependency somewhere?

[UziTech]

The issue with jest@26 might be related to https://github.com/smooth-code/jest-puppeteer/issues/421

[lfdebrux]

I've made a more minimal example that doesn't include jest at all: https://github.com/lfdebrux/test-jest-dev-server/tree/no-jest

The really strange thing is that on my machine the log message dev server is running is printed before the error message from the dev server:

# in one terminal
% python -m http.server 3000

# in another terminal
% node test.js 
dev server is running
node:events:368
      throw er; // Unhandled 'error' event
      ^

Error: listen EADDRINUSE: address already in use 0.0.0.0:3000
    at Server.setupListenHandle [as _listen2] (node:net:1334:16)
    at listenInCluster (node:net:1382:12)
    at doListen (node:net:1520:7)
    at processTicksAndRejections (node:internal/process/task_queues:84:21)
Emitted 'error' event on Server instance at:
    at emitErrorNT (node:net:1361:8)
    at processTicksAndRejections (node:internal/process/task_queues:83:21) {
  code: 'EADDRINUSE',
  errno: -48,
  syscall: 'listen',
  address: '0.0.0.0',
  port: 3000
}

I'm not sure what this means. It's possible that its a macOS thing, I haven't tested on other systems.

[josephwynn-sc]

Just chiming in to say that I have this issue on my Macbook but not my other laptop running Linux, which might confirm the previous commenter's suspicion that this is a macOS thing.