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stream: prefer sync iterator in fromSync#64294

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trivikr:stream-iter-fromsync-iter
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stream: prefer sync iterator in fromSync#64294
trivikr wants to merge 1 commit into
nodejs:mainfrom
trivikr:stream-iter-fromsync-iter

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@trivikr

@trivikr trivikr commented Jul 4, 2026

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Fixes: #64292

stream/iter's fromSync() rejected any input that exposed
Symbol.asyncIterator, even when the same input also exposed
Symbol.iterator.

This updates fromSync() to reject only inputs without a synchronous
iteration path, allowing dual sync/async iterables and thenable sync
iterables to be consumed through their synchronous iterator.


Assisted-by: openai:gpt-5.5

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Review requested:

  • @nodejs/streams

@nodejs-github-bot nodejs-github-bot added needs-ci PRs that need a full CI run. stream Issues and PRs related to the stream subsystem. labels Jul 4, 2026
@trivikr trivikr added the request-ci Add this label to start a Jenkins CI on a PR. label Jul 4, 2026
Comment thread lib/internal/streams/iter/from.js Outdated

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lgtm

@github-actions github-actions Bot removed the request-ci Add this label to start a Jenkins CI on a PR. label Jul 5, 2026
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When an input provides Symbol.iterator, fromSync() should consume the
synchronous iterator instead of rejecting the input because it also
exposes an asynchronous or promise-like protocol.

Continue rejecting async-only iterables and promise/thenable-only
inputs, but allow sync iterables that also define Symbol.asyncIterator
or then().

Signed-off-by: Kamat, Trivikram <16024985+trivikr@users.noreply.github.com>
Assisted-by: openai:gpt-5.5
@trivikr trivikr force-pushed the stream-iter-fromsync-iter branch from 1e713e7 to f21d604 Compare July 6, 2026 06:17
@trivikr trivikr requested a review from aduh95 July 6, 2026 06:20
@trivikr trivikr added the request-ci Add this label to start a Jenkins CI on a PR. label Jul 6, 2026
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stream/iter: fromSync() rejects dual sync/async iterables instead of using Symbol.iterator

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