Showing port number are different between Vite and Kit if 3000 is already in use

[baseballyama]

Describe the bug

When I run npm run dev in kit project,
Different port shows if 3000 is already in use as you can see from the log.

Reproduction

After use 3000 port by some process, run this commands.

yes "" | npm init svelte my-app
cd my-app
npm install
npm run dev

Logs

vite v2.5.7 dev server running at:

  > Local: http://localhost:3001/
  > Network: use `--host` to expose

  SvelteKit v1.0.0-next.169

  network: not exposed
  network: not exposed
  local:   http://localhost:3000

  Use --host to expose server to other devices on this network

System Info

System:
    OS: Windows 10 10.0.19043
    CPU: (8) x64 Intel(R) Core(TM) i7-8550U CPU @ 1.80GHz  
    Memory: 2.55 GB / 15.86 GB
  Binaries:
    Node: 14.17.0 - C:\Program Files\nodejs\node.EXE       
    npm: 6.14.13 - C:\Program Files\nodejs\npm.CMD
  Browsers:
    Edge: Spartan (44.19041.1023.0), Chromium (93.0.961.52)
    Internet Explorer: 11.0.19041.1202
  npmPackages:
    @sveltejs/kit: next => 1.0.0-next.170
    svelte: ^3.34.0 => 3.42.6

Severity

annoyance

Additional Information

Maybe packages\kit\src\cli.js#welcome should be removed most of the code??

https://github.com/sveltejs/kit/blob/master/packages/kit/src/cli.js#L217

And the output should be like this?

  vite v2.5.7 dev server running at:

  > Local: http://localhost:3000/
  > Network: use `--host` to expose

  SvelteKit v1.0.0-next.169

  Use --host to expose server to other devices on this network

Thank you.

[bluwy]

The duplicated welcome messages likely came from #2232, I think the best case is if we can replace vite v2.5.7 dev server with SvelteKit v1.0.0-next.169, though that's tricky. Otherwise having a SvelteKit v1.0.0-next.169 message below vite's might be fine too.

[benmccann]

I thought kit would exit if the port were already in use:

kit/packages/kit/src/cli.js

Line 206 in d8efaa2

process.exit(1);

I'm not sure why it's still running. But it looks like the message is being printed here:

kit/packages/kit/src/cli.js

Line 217 in d8efaa2

function welcome({ port, host, https, open }) {

[baseballyama]

@benmccann

When I create #2441, you said we can use a port dynamically after merge #2232.
So I thought that now running on 3001 is expected behavior.
But the actual spec is that it should stop a server if 3000 is already in use??

And if we should stop a server if port 3000 is already in use,
perhaps we need to update port-authority as already mentioned at #948 (comment).
(But still, I didn't dig so I need to check more according to your answer.)

[benmccann]

I don't think SvelteKit should have port checking code since it already exists in Vite. But it's there and it's surprising to me that it's not working on your machine. It does work for me on Linux. I guess it doesn't work on Windows. But anyway, we should probably remove that code

[benmccann]

I sent a PR to Vite to remove the log messages that it's printing: vitejs/vite#5016

We should still remove our port choosing logic in favor of Vite's strictPort option and cleanup some stuff on our end, but maybe I will wait to see what happens with the Vite PR first since that may affect exactly what changes on our end

[bluwy]

Do we want to remove the log messages entirely? We wouldn't know what the URL is ahead of time if strictPort: false (which is default for Vite). The same may apply to the network URL too, unless we duplicate Vite's code.

[benmccann]

I was thinking we'd update our code to check what port the server was running on after it started

[bluwy]

Ah if there's a way to get the port after createServer. It would be fine then.

[baseballyama]

This is just an update current situation.

vitejs/vite#5016 was merged (Thank you @benmccann).
So I tried to run dev and preview commands.
And I share the result.

dev

  SvelteKit v1.0.0-next.174

  network: not exposed
  network: not exposed
  local:   http://localhost:3000

  Use --host to expose server to other devices on this network

The duplicate message is gone👍.
But if 3000 port is used, local message is wrong.

So we should change args for welcome function.
And we should remove check_port.

const { server } = watcher.vite.config;
welcome({ port: server.port, host: server.host, https: host.https, open });

Preview

If 3000 is free, it works fine.

  SvelteKit v1.0.0-next.174

  network: not exposed
  network: not exposed
  local:   http://localhost:3000

  Use --host to expose server to other devices on this network

But 3000 is already in use, below error comes (I'm using Windows10).

  SvelteKit v1.0.0-next.174

  network: not exposed
  network: not exposed
  local:   http://localhost:3000

  Use --host to expose server to other devices on this network


events.js:353
      throw er; // Unhandled 'error' event
      ^

Error: listen EADDRINUSE: address already in use 127.0.0.1:3000
    at Server.setupListenHandle [as _listen2] (net.js:1318:16)
    at listenInCluster (net.js:1366:12)
    at GetAddrInfoReqWrap.doListen [as callback] (net.js:1503:7)
    at GetAddrInfoReqWrap.onlookup [as oncomplete] (dns.js:69:8)
Emitted 'error' event on Server instance at:
    at emitErrorNT (net.js:1345:8)
    at processTicksAndRejections (internal/process/task_queues.js:82:21) {
  code: 'EADDRINUSE',
  errno: -4091,
  syscall: 'listen',
  address: '127.0.0.1',
  port: 3000
}
 ELIFECYCLE  Command failed with exit code 1.

Preview doesn't use Vite, right?
If yes, to have the same behavior between dev and preview needs to take effort I think.
So if we regard this preview behavior as correct, then we don't need to do anything.

[bluwy]

Thanks to vitejs/vite#5014, we can use Vite's preview for that as well. Though that feature is still in beta, and it would take another week (I think) before Vite releases a stable 2.6.0 version.

For dev I think we should follow your proposed solution. For preview however, we could try a best-effort fix for now or leave it as is and wait for Vite (?).

[baseballyama]

Oh sorry, I forgot about vitejs/vite#5014.

We should both dev and preview depend on Vite to avoiding program duplication.
So I think we should wait for Vite's preview function to be ready to use in my opinion.
And now we can keep current code of preview. (Do nothing for now for preview)