Inconsistent behavior of `stdio[3]: 'ignore'`

Version

v21.7.2

Platform

Linux my-laptop 6.5.0-26-generic #26-Ubuntu SMP PREEMPT_DYNAMIC Tue Mar 5 21:19:28 UTC 2024 x86_64 x86_64 x86_64 GNU/Linux

Subsystem

child_process

What steps will reproduce the bug?

With print.js:

import {writeSync} from 'node:fs'

const fdNumber = Number(process.argv[2])
writeSync(fdNumber, '.')

With example.js:

import {spawn} from 'node:child_process'

spawn('node', ['./print.js', '1'], {stdio: ['pipe', 'ignore', 'inherit', 'ignore']})

Prints nothing. But:

import {spawn} from 'node:child_process'

spawn('node', ['./print.js', '3'], {stdio: ['pipe', 'ignore', 'inherit', 'ignore']})

Prints the following:

node:fs:933
  handleErrorFromBinding(ctx);
  ^

Error: EINVAL: invalid argument, write
    at writeSync (node:fs:933:3)
    at file:///home/ether/Desktop/print.js:4:1
    at ModuleJob.run (node:internal/modules/esm/module_job:222:25)
    at async ModuleLoader.import (node:internal/modules/esm/loader:323:24)
    at async loadESM (node:internal/process/esm_loader:28:7)
    at async handleMainPromise (node:internal/modules/run_main:120:12) {
  errno: -22,
  syscall: 'write',
  code: 'EINVAL'
}

Node.js v21.7.2

How often does it reproduce? Is there a required condition?

No.

What is the expected behavior? Why is that the expected behavior?

ignore should behave consistently regardless of the same descriptor.

What do you see instead?

ignore's behavior differs between stdio[1] and stdio[3].

Additional information

I understand the reason might be that child processes should always have a stdin/stdout/stderr even when ignored, while this does not apply to other file descriptors. So stdio[3]: 'ignore' probably results in no file descriptor being created, as opposed to stdio[1]: 'ignore'.

On one hand, the current behavior is more efficient, as it does not waste creating a file descriptor that's not going to be used.
On the other hand, this results in inconsistent behavior.

Any change there would be breaking too. So this probably won't be fixed, but I reported it in case this was not intentional.

print.js と example.js から再現手順を実行して、stdio[1] と stdio[3] の違いを確認します。次に、child_process の実装と関連するテストを調べ、ディスクリプタの挙動が意図的なものかどうかを判断します。挙動がテストカバレッジと一貫するようにされるか、または互換性に関わるその根拠が文書化された形で確立されれば完了です。