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doc: further fix async iterator example
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Further fixes an issue with the async iterator example where an
incorrect assumption was made in regards that drain or error
is always invoked after !write().

Fixes: #31365

PR-URL: #31367
Reviewed-By: Matteo Collina <[email protected]>
Reviewed-By: Luigi Pinca <[email protected]>
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ronag authored and codebytere committed Feb 17, 2020
1 parent 15b24b7 commit 729b961
Showing 1 changed file with 12 additions and 2 deletions.
14 changes: 12 additions & 2 deletions doc/api/stream.md
Original file line number Diff line number Diff line change
Expand Up @@ -2644,12 +2644,22 @@ const finished = util.promisify(stream.finished);

const writable = fs.createWriteStream('./file');

function drain(writable) {
if (writable.destroyed) {
return Promise.reject(new Error('premature close'));
}
return Promise.race([
once(writable, 'drain'),
once(writable, 'close')
.then(() => Promise.reject(new Error('premature close')))
]);
}

async function pump(iterable, writable) {
for await (const chunk of iterable) {
// Handle backpressure on write().
if (!writable.write(chunk)) {
if (writable.destroyed) return;
await once(writable, 'drain');
await drain(writable);
}
}
writable.end();
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