stream: add dump()/dumpSync() for stream/iter by Ethan-Arrowood · Pull Request #65598 · nodejs/node

Ethan-Arrowood · 2026-08-27T18:18:30Z

Adds dump() and dumpSync() to node:stream/iter.

This will enable us to replace for await loops with await dump(stream) across the repo.

- for await (const _ of stream) { /* drain */ } // eslint-disable-line no-unused-vars+ await dump(stream);

I used two commits: one for the feature, another for the migration so it's easy to review.

I only migrated tests that were already using iter streams. But there are more that could benefit from this util.

This api is inspired by things like Undici's body.dump() method.

Let me know what you think of this API addition!

nodejs-github-bot · 2026-08-27T18:18:36Z

Review requested:

@nodejs/quic
@nodejs/streams

codecov · 2026-08-27T20:11:40Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.15%. Comparing base (1e9fd95) to head (2db8a62).
⚠️ Report is 25 commits behind head on main.

Additional details and impacted files

@@ Coverage Diff @@## main #65598 +/- ##
==========================================
- Coverage 90.17% 90.15% -0.02% 
==========================================
Files 769 769 Lines 261448 261545 +97 Branches 49674 49668 -6 ==========================================
+ Hits 235759 235806 +47 - Misses 16736 16775 +39 - Partials 8953 8964 +11

Files with missing lines	Coverage Δ
lib/internal/streams/iter/consumers.js	`97.12% <100.00%> (+0.35%)`	⬆️
lib/stream/iter.js	`100.00% <100.00%> (ø)`

... and 34 files with indirect coverage changes

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nodejs-github-bot · 2026-08-27T22:35:09Z

CI: https://ci.nodejs.org/job/node-test-pull-request/76607/

pimterry

Very onboard with the concept, implementation looks good, small point on a test case.

Larger question though: can we rename this? Drain is a separate related but different concept on the writer API. Giving them the same name is a bit confusing, and hits practical issues as well (like the various tests here that have to rename existing drain references that mean something else).

dump() or discard()?

pimterry · 2026-08-28T16:05:50Z

+// drain: does not retain data
+// =============================================================================
+
+async function testDrainDoesNotRetain() {


This doesn't really do what it says it does - as is it roughly duplicates testDrainConsumesToCompletion I think. It allocates the buffer once outside the source, so it can't check what's retained anyway. Needs a buffer per chunk with a WeakRef & GC dance if you want to test this I think.

Ethan-Arrowood · 2026-08-28T17:11:48Z

I'm okay with considering a different name. Honestly, I stuck with drain() because it was in the comments of the code blocks this is meant to replace for await (const _ of stream) { /* drain */ }. But Undici uses dump(). I also like discard().

Let the bikeshedding begin!

jasnell · 2026-08-29T03:10:28Z

consume()?

Ethan-Arrowood · 2026-08-31T18:11:40Z

I feel like consume implies its being used somehow. Like all the other methods "consume" the stream and then return something.

I think dump() is the way to go. Undici set some precedent with body.dump().

Can people +1 this comment if they agree on dump()? Otherwise, please bikeshed whatever other name. I'd prefer not to block this too long on the name.

Ethan-Arrowood · 2026-09-04T13:59:30Z

We agreed on dump() on a recent QUIC team meeting call. I've renamed it now and updated everything except the branch name. Please re review and I'll get the CI kicked off. Thank you!

nodejs-github-bot · 2026-09-04T14:41:05Z

CI: https://ci.nodejs.org/job/node-test-pull-request/76977/

bjohansebas

LGMT!

mcollina

lgtm

nodejs-github-bot · 2026-09-04T15:24:22Z

CI: https://ci.nodejs.org/job/node-test-pull-request/76980/

Ethan-Arrowood · 2026-09-04T16:17:22Z

Good catch, fixing now.

Every consumer in node:stream/iter retains what it reads, so there is no way to read a streamable to completion while keeping nothing. To clear a stream, callers write `for await (const _ of source) {}`. This is apparent throughout multiple test suites, including the stream/iter tests themselves. These are especially useful for QUIC where a receiver doesn't want the payload, but still has to read it to completion to relieve backpressure. bytes() does that too, but allocates the whole payload to discard it. dump() pulls every batch and drops it, so peak memory is one batch regardless of volume. It takes the same signal and limit options as the other consumers, rejects if the source errors mid-stream, and fulfills with undefined. dumpSync() is the synchronous form. The name follows undici's body.dump(). drain() was the obvious alternative but this module already exports ondrain() and drainableProtocol() for writer-side backpressure, which is the opposite side of the pipe. Assisted-by: Claude Opus 5 Signed-off-by: Ethan Arrowood <ethan@arrowood.dev>

Replaces the `for await (const _ of source) {}` discard idiom with dump(), which says what it does and does not need an eslint-disable for the unused loop variable. 89 loops across 60 files, plus 32 now redundant eslint-disable directives and comments removed. Only files that already declare --experimental-stream-iter are converted, so no test gains an experimental flag it did not already opt into. That leaves 21 files with the old idiom; converting those would change what those tests run under and belongs in a separate discussion. Loops that break early are left alone: those cancel the source rather than reading it to completion, which is not what dump() does. Assisted-by: Claude Opus 5 Signed-off-by: Ethan Arrowood <ethan@arrowood.dev>

Ethan-Arrowood · 2026-09-04T16:30:00Z

My bad @pimterry . I manually reviewed the updates now for any erroneous find/replaces, looks all good to me.

nodejs-github-bot · 2026-09-04T21:17:27Z

CI: https://ci.nodejs.org/job/node-test-pull-request/76995/

nodejs-github-bot added needs-ci PRs that need a full CI run. stream Issues and PRs related to Node.js streams. labels Aug 27, 2026

Ethan-Arrowood requested review from jasnell, pimterry and trivikr August 27, 2026 18:18

Ethan-Arrowood added the quic Issues and PRs related to the QUIC transport implementation. label Aug 27, 2026

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Ethan-Arrowood mentioned this pull request Aug 27, 2026
add dump/dumpSync for consuming stream WinterTC55/iter-streams#28
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Ethan-Arrowood force-pushed the stream-iter-drain branch from 2e586f3 to e1e8ca0Compare September 4, 2026 13:57

Ethan-Arrowood changed the title ~~stream: add drain()/drainSync() for stream/iter~~stream: add dump()/dumpSync() for stream/iterSep 4, 2026

Ethan-Arrowood requested review from benjamingr, jasnell, metcoder95 and pimterry September 4, 2026 13:59

Ethan-Arrowood force-pushed the stream-iter-drain branch from a24f864 to ccf6409Compare September 4, 2026 14:15

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Comment threaddoc/api/quic.md Outdated
Comment threadlib/internal/streams/iter/consumers.js Outdated

Ethan-Arrowood added 2 commits September 4, 2026 10:21

Ethan-Arrowood force-pushed the stream-iter-drain branch from ccf6409 to 2db8a62Compare September 4, 2026 16:25

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