Process hangs after calling `readline.emitKeypressEvents` and having attached a "keypress" event handler

[fabiospampinato]

Version

v16.13.0

Platform

Darwin MBP.local 21.2.0 Darwin Kernel Version 21.2.0: Sun Nov 28 20:28:41 PST 2021; root:xnu-8019.61.5~1/RELEASE_ARM64_T6000 arm64

Subsystem

No response

What steps will reproduce the bug?

When executing the following code the process never exits:

const readline = require ( 'readline' );

process.stdin.setRawMode ( true );

readline.emitKeypressEvents ( process.stdin );

const cb = () => {};

process.stdin.on ( 'keypress', cb );
process.stdin.off ( 'keypress', cb );

Interestingly when executing the following it exits:

const readline = require ( 'readline' );

process.stdin.setRawMode ( true );

readline.emitKeypressEvents ( process.stdin );

const cb = () => {};

// process.stdin.on ( 'keypress', cb );
// process.stdin.off ( 'keypress', cb );

And when executing the following it exits too:

const readline = require ( 'readline' );

process.stdin.setRawMode ( true );

// readline.emitKeypressEvents ( process.stdin );

const cb = () => {};

process.stdin.on ( 'keypress', cb );
process.stdin.off ( 'keypress', cb );

So it's not attaching the event handler nor calling readline.emitKeypressEvents on their own that cause the issue, but when both things are done for whatever reason the process never exits, even if I remove the event handler.

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

Always.

What is the expected behavior?

The process shouldn't hang for nothing.

What do you see instead?

The process hangs for (what seems to be) nothing.

Additional information

No response

[fabiospampinato]

The following works:

const readline = require ( 'readline' );

const interface = readline.createInterface ({ input: process.stdin, escapeCodeTimeout: 50 });

process.stdin.setRawMode ( true );

readline.emitKeypressEvents ( process.stdin, interface );

const cb = () => {};

process.stdin.on ( 'keypress', cb );
process.stdin.off ( 'keypress', cb );

interface.close ();

So this interface thing is required to make this work properly, it looks like a bug to me. If it's not a bug it should at least be documented somewhere.