fix(server): drain stdin when not interactive

[thatguystone]

Description

If stdin.on('data') isn't called, 'end' is never emitted. This works in interactive mode (ie. stdin.isTTY) since readline drains stdin.

[bluwy]

Can you give a repro or show an example of what this fixes? In what case would you run a dev server in non-interactive mode in non-CI?

[thatguystone]

Can you give a repro or show an example of what this fixes?

import subprocess
import sys

proc = subprocess.Popen(
    ["./node_modules/.bin/vite"],
    stdin=subprocess.PIPE,
    stdout=sys.stdout,
    stderr=sys.stderr,
)
proc.stdin.close()
proc.wait(timeout=1.0)

In this case, pre-patch, it fails with TimeoutExpired, and vite will continue running indefinitely in the background. For the CI and non-CI case, vite should probably reliably exit when its stdin is closed.

import subprocess
import sys

proc = subprocess.Popen(
    ["./node_modules/.bin/vite"],
    stdin=sys.stdin,
    stdout=sys.stdout,
    stderr=sys.stderr,
)

When run with stdin.isTTY, vite continues in the background but eventually exits with:

node:events:486
      throw er; // Unhandled 'error' event
      ^

Error: read EIO
    at TTY.onStreamRead (node:internal/stream_base_commons:216:20)
Emitted 'error' event on Interface instance at:
    at ReadStream.onerror (node:internal/readline/interface:259:10)
    at ReadStream.emit (node:events:508:28)
    at emitErrorNT (node:internal/streams/destroy:170:8)
    at emitErrorCloseNT (node:internal/streams/destroy:129:3)
    at process.processTicksAndRejections (node:internal/process/task_queues:90:21) {
  errno: -5,
  code: 'EIO',
  syscall: 'read'
}

Node.js v24.8.0

In what case would you run a dev server in non-interactive mode in non-CI?

I run vite serve with a number of other services, all managed by a single runner; a couple of them can run in interactive mode, but it doesn't make much sense for them all to fight over stdin, so none get stdin.

[bluwy]

Thanks for the explanation! Makes sense to me

[thatguystone]

Can this be merged?

[kentcdodds]

Sadly this broke my use case: #20884

[laurentpayot]

For the record, it also broke my F# (.Net) launch of a vite preview process. Only working in a brand new shell window.