`readline` module yields wrong and incomplete values with a bad performance (compared to NodeJS) about bun HOT 2 OPEN

This does only seem to happen, if you use a for await loop, right? For me it works fine with:

rl.on('line', (line) => {
  console.log(typeof line, line)
}

Had a quick look, what might cause the problem with await, and maybe these blocks of code are worth investigating.
As far as I can see, the AsyncIterator of readline uses EventEmitter.on:

In there, the event return value ev is always wrapped in an array, as this is the default behaviour for node.js as well. (Does anyone know why that is? Seems counter intuitive to me.):

In node.js' implementation though, setting the option kFirstEventParam: true does skip the array collection step and returns the value as is:
https://github.com/nodejs/node/blob/a8de25ed1523594dd6bf0ee08a24f146d38cb4e8/lib/events.js#L1158-L1160

The kFirstEventParam option does not seem to be implemented in bun at the moment and that's probably why the lines are wrapped in an array in your example.

I do not have a bun dev environment set-up right now to check, so this might be wrong.

Still does not explain why the read-in stops after 3 rows.

from bun.

Related: #8370

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