child_process 'close' always (?) emitted after 'exit'

[addaleax]

• Version: master
• Platform: Linux 5.4.0-70-generic Mani #78-Ubuntu SMP Fri Mar 19 13:29:52 UTC 2021 x86_64 x86_64 x86_64 GNU/Linuxd
• Subsystem: child_process

What steps will reproduce the bug?

const child_process = require('child_process');
const proc = child_process.spawn('bash', ['-c', 'exec 0>&- 1>&- 2>&-; sleep 5'], {
  stdio: ['inherit', 'pipe', 'inherit']
});
proc.stdout.pipe(process.stdout);
proc.on('exit', () => console.log('exit'));
proc.on('close', () => console.log('close'));

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

Always

What is the expected behavior?

'close' should be emitted immediately (all stdio streams are closed), 'exit' after 5 seconds

What do you see instead?

5 seconds pass, then 'exit' is emitted and then 'closed'

[Linkgoron]

IMO this is a documentation issue, or at least this is the expected original behavior of 'close'. IMO this is also reflected in the callback arguments, which are either an exit code or a kill signal, which can only be provided if the process is finished. I'm not saying that the current behavior is correct, just that it's IMO what I would expect from the documentation.

[addaleax]

@Linkgoron That’s fair, and it’s okay to say we don’t want to break this behavior by changing it, but in that case, it would really be nice to document this.