stream: Add option to `Readable.take` operator to not close the stream
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feature request
stream
- Dominant language
- JavaScript
- Stars
- 122k
- Forks
- 37.3k
- Avg merge
- 4d 2h
- Merged PRs (30d)
- 283
Description
What is the problem this feature will solve?
I will be able to do this:
const csvParsedStream = fs
.createReadStream('file.csv')
.compose(csvParse({ columns: false }));
const [columns] = await csvParsedStream
.take(1)
.toArray();
// This will now be empty and no data as take already consumed the stream
const parsed = await csvParsedStream
.map((row) => parseRowByColumns(row, columns))
.toArray();
Another example (I know I can use [first, ...rest] this is just an example):
const a = Readable.from([1, 2, 3, 4, 5, 6, 7, 8, 9, 10]);
const [first] = await a.take(1).toArray();
console.log(first);
// [1]
const rest = await a.toArray();
console.log(rest)
// []
What is the feature you are proposing to solve the problem?
Adding closeStream option to the take operator that with default value true that I could disable closing the stream
const csvParsedStream = fs
.createReadStream('file.csv')
.compose(csvParse({ columns: false }));
const [columns] = await csvParsedStream
.take(1, { closeStream: false }) // Right now this would close the stream, but we give it an option to not
.toArray();
const parsed = await csvParsedStream.map((row) => parseRowByColumns(row, columns)).toArray();
What alternatives have you considered?
Get the first value from stream as async itarator and rest
let columns;
for await (const c of csvParsedStream.iterator<string[]>({ destroyOnReturn: false })) {
columns = c;
break;
}
const parsed = await csvParsedStream
.map((row) => parseRowByColumns(row, columns))
.toArray();
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start at the Readable.take operator and compare its current stream-closing behavior with the mentioned async iterator({ destroyOnReturn: false }) alternative. Review the surrounding stream API discussion and define completion as supporting the proposed closeStream option while preserving the existing default behavior.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- javascript, node.js
- Domain
- api, backend
- Issue type
- Feature
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Quiet
- Clarity
- Mostly clear
- Newbie friendliness
- 45/100