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stream/iter: pending next() hangs after iterator return() #63519
Description
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
Activity
trivikr commentedon May 28, 2026
The bug in push was fixed in #63555, when fixing for
iterator.throw()stream: settle pending broadcast reads on return
stream: settle pending broadcast reads on return
stream: settle pending broadcast reads on return