Given the examples of using async generators with writable streams https://nodejs.org/dist/latest-v12.x/docs/api/stream.html#stream_piping_to_writable_streams_from_async_iterators.
There seems to be an issue in that they can cause an unhandled exception if 'error' is emitted after 'finish' (which is currently possible in some cases even with core streams). once will release the 'error' handler on completion ('finish'). I would personally discourage using it as in the example, i.e.
I would replace:
UNSAFE
const { once } = require('events');
const writable = fs.createWriteStream('./file');
(async function() {
const readable = Readable.from(iterator);
readable.pipe(writable);
// Ensure completion without errors.
await once(writable, 'finish');
})();with
SAFE
const finished = util.promisify(stream.finished);
const writable = fs.createWriteStream('./file');
(async function() {
const readable = Readable.from(iterator);
readable.pipe(writable);
// Ensure completion without errors.
await finished(writable);
})();or
const pipeline = util.promisify(stream.pipeline);
const writable = fs.createWriteStream('./file');
(async function() {
const readable = Readable.from(iterator);
await pipeline(readable, writable);
})();and
UNSAFE
const { once } = require('events');
const writable = fs.createWriteStream('./file');
(async function() {
for await (const chunk of iterator) {
// Handle backpressure on write().
if (!writable.write(chunk))
await once(writable, 'drain');
}
writable.end();
// Ensure completion without errors.
await once(writable, 'finish');
})();with
SAFE
const { once } = require('events');
const finished = util.promisify(stream.finished);
const writable = fs.createWriteStream('./file');
(async function() {
for await (const chunk of iterator) {
// Handle backpressure on write().
if (!writable.write(chunk))
await once(writable, 'drain');
}
writable.end();
// Ensure completion without errors.
await finished(writable);
})();Possibly with a note on why once is not appropriate in this situation.
Given the examples of using async generators with writable streams https://nodejs.org/dist/latest-v12.x/docs/api/stream.html#stream_piping_to_writable_streams_from_async_iterators.
There seems to be an issue in that they can cause an unhandled exception if
'error'is emitted after'finish'(which is currently possible in some cases even with core streams).oncewill release the'error'handler on completion ('finish'). I would personally discourage using it as in the example, i.e.I would replace:
UNSAFE
with
SAFE
or
and
UNSAFE
with
SAFE
Possibly with a note on why
onceis not appropriate in this situation.