stream/iter: pending next() hangs after iterator return()

[trivikr]

Version

26.2.0

Platform

macOS 26.5.0

Subsystem

stream

What steps will reproduce the bug?

import { broadcast, push } from 'node:stream/iter';

async function check(name, pendingNext) {
  const result = await Promise.race([
    pendingNext.then(
      (value) => ({ status: 'settled', value }),
      (error) => ({ status: 'rejected', error }),
    ),
    new Promise((resolve) => {
      setTimeout(() => resolve({ status: 'timeout' }), 100);
    }),
  ]);

  if (result.status === 'timeout') {
    console.log(`${name}: observed hang; expected pending next() to settle after return()`);
  } else {
    console.log(`${name}: settled`, result);
  }
}

{
  const { readable } = push();
  const iter = readable[Symbol.asyncIterator]();

  const pendingNext = iter.next();
  await iter.return();

  await check('push()', pendingNext);
}

{
  const { broadcast: bc } = broadcast();
  const iter = bc.push()[Symbol.asyncIterator]();

  const pendingNext = iter.next();
  await iter.return();

  await check('broadcast()', pendingNext);
}

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

Always

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

push(): settled {
  status: 'settled',
  value: [Object: null prototype] { value: undefined, done: true }
}
broadcast(): settled {
  status: 'settled',
  value: [Object: null prototype] { done: true, value: undefined }
}

pendingNext should settle after await iter.return(), normally as { value: undefined, done: true } or a rejection, so no read promise is left unresolved.

What do you see instead?

push(): observed hang; expected pending next() to settle after return()
broadcast(): observed hang; expected pending next() to settle after return()

pendingNext stays pending and the timeout wins, because next() stores a resolver for the empty read, but return() detaches/cleans up without resolving or rejecting that stored pending read.

Additional information

No response