Unable to completely read data from 'bytes' ReadableStream

[debadree25]

Version

20.2.0

Platform

Darwin Debadree-MacBook-Pro.local 22.4.0 Darwin Kernel Version 22.4.0: Mon Mar 6 21:00:17 PST 2023; root:xnu-8796.101.5~3/RELEASE_X86_64 x86_64

Subsystem

Web streams

What steps will reproduce the bug?

Run the following script in node and in chrome

const toPull = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j'];
const st = new ReadableStream({
  type: 'bytes',
  start(controller) {},

  pull(controller) {
    const chunk = toPull.shift();
    if (chunk === undefined) {
      controller.close();
      return;
    }

    controller.enqueue(new TextEncoder().encode(chunk));
  },
});

const reader = st.getReader({ mode: 'byob' });
const chunks = [];

const decoder = new TextDecoder();

let result;
do {
  result = await reader.read(new Uint8Array(100));
  if (result.value !== undefined)
    chunks.push(decoder.decode(result.value));
} while (!result.done);

console.log(chunks);

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

Always

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

[
  'a', 'b', 'c', 'd',
  'e', 'f', 'g', 'h',
  'i', 'j'
]

The stream should consume all the elements in the toPull array and we must be able to subsequently read this data back, the behaviour is correct in chrome.

What do you see instead?

No output

debadreechatterjee@Debadree-MacBook-Pro node % node test3.mjs
debadreechatterjee@Debadree-MacBook-Pro node % 

Additional information

I tried investigating a little, its possible that there is some hanging promise before the closing of the stream. for example if you logged the values in each step the output would be like this

debadreechatterjee@Debadree-MacBook-Pro node % node test3.mjs
read value a
read value b
read value c
read value d
read value e
read value f
read value g
read value h
read value i
read value j
debadreechatterjee@Debadree-MacBook-Pro node %

note that console to print the chunks array is not printed

[debadree25]

Also cc @nodejs/whatwg-stream

[Linkgoron]

I found the issue and have a fix, I'll create a PR later.

From what I've found, readableStreamClose incorrectly handles only StreamDefaultReader correctly and not BYOB. If you look at readableStreamError in comparison it handles both BYOB and default.

[Linkgoron]

I take back my previous statement... I think I understand what the issue is, and I managed to create a fix (at least it passed both wpt tests and Node's own tests) - however as I understand it - the implementation is directly from the spec. I checked and this also reproduces on Deno as well.

[debadree25]

Thats quite weird
is the spec wrong or does chrome deviate from the spec?

[Linkgoron]

Thats quite weird is the spec wrong or does chrome deviate from the spec?

I just tried executing your code in the devtools, and I see the same behavior as in Node and Deno.

Simpler example:

const st = new ReadableStream({
  type: 'bytes',
  start(controller) {},

  pull(controller) {
    controller.close();
  },
});

const reader = st.getReader({ mode: 'byob' });
const decoder = new TextDecoder();
console.log('before')
result = await reader.read(new Uint8Array(100));
console.log('after');

[debadree25]

This is indeed spec compliant behvaiour in order to end byob streams we have to send a controller.byobRequest.respond(0); ref: https://streams.spec.whatwg.org/#example-rbs-pull