stream/iter: pull() swallows abort when async transform flush resolves to null

[trivikr]

Version

main

Platform

N/A

Subsystem

stream

What steps will reproduce the bug?

import { pull, text } from 'node:stream/iter';

const controller = new AbortController();
const reason = new Error('boom');

const transform = async (chunks) => {
  if (chunks !== null) return chunks;

  controller.abort(reason);
  return null;
};

text(pull('x', transform, { signal: controller.signal })).then(
  (value) => console.log('fulfilled:', JSON.stringify(value)),
  (error) => console.log('rejected:', error === reason, error),
);

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

Always

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

rejected: true Error: boom

The pipeline should reject with reason, making error === reason true. An abort during transform flushing should not be converted into normal iterator completion.

From §9.1, Stream.pull(), steps 5–7:

If signal is not undefined, set pipelineController’s signal to follow signal.

What do you see instead?

fulfilled: "x"

The pipeline fulfills successfully with "x", even though its signal was aborted while the asynchronous flush was completing. The abort reason is never delivered to the consumer.

Additional information

No response