ReadableStream detaches buffer pool (??)

[devsnek]

Version

17.0.0-pre

Platform

n/a

Subsystem

stream/web

What steps will reproduce the bug?

new ReadableStream({
	type: 'bytes',
	start(c) {
		c.enqueue(Buffer.from('hi'));
		c.close();
	},
}).getReader();

Buffer.from('hi!'); // TypeError: Cannot perform Construct on a detached ArrayBuffer

cc @jasnell

[jasnell]

So. Yeah... This one is fun. It's actually a requirement of the spec...

See https://streams.spec.whatwg.org/#readable-byte-stream-controller-enqueue

Specifically, step 7 ... Let transferredBuffer be ? TransferArrayBuffer(buffer)

If we look at the definition of TransferArrayBuffer:

[devsnek]

Yeah... i think we should do something though, this is a pretty annoying footgun as-is. I think if the backing buffer is the pool, we could either do nothing (which seems reasonable to me) or make a copy if people feel uncomfortable about doing nothing.

[jasnell]

Yeah, we'll just need to be clear that it's a break from the spec in those cases, and we need to be careful with cross-worker flows to make sure we don't break anything. Making a copy seems to be the safest.