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…entry is a function pipelineImpl wraps the output of a function tail in a PassThrough so the callback API can pipe it further. The promise API never exposes that stream, so nothing read it and the pump stalled at the high water mark. Resume it after pipelineImpl returns, as nodejs/node#65559 does.
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WalkthroughThe promise-based ChangesStream pipeline completion
Priority: Severity of issue fixed: Medium Merge Risk:
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| Check name | Status | Explanation |
|---|---|---|
| Title check |  |
The title clearly identifies the main change: resuming the proxy stream when the final pipeline entry is a function. |
| Linked Issues check | |
Active issue [#45724] requires stream/promises.pipeline() to settle when an async generator is the final entry and output exceeds the high-water mark. src/js/internal/stream.promises.ts retains `p… |
| Out of Scope Changes check | |
The implementation directly addresses [#45724]. The tests verify high-water-mark completion, error handling, API variants, web-stream output, and the callback API's paused return stream. These changes… |
| Description check | |
The pull request description is complete. It explains the problem, the implementation, compatibility considerations, downsides, and verification steps. The Problem and Fix sections provide the informa… |
Full details: Linked Issues check
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Explanation
Active issue [
#45724] requiresstream/promises.pipeline()to settle when an async generator is the final entry and output exceeds the high-water mark.src/js/internal/stream.promises.tsretainspipelineImpl's returned stream, detects a function tail in both spread and single-array forms, and resumes the readable proxy stream. Tests cover 100 chunks, the array form, options,Stream.promises.pipeline, andutil.promisify(Stream.pipeline). Issue [#40685] is closed historical context and adds no coding requirement.
Full details: Out of Scope Changes check
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Explanation
The implementation directly addresses [
#45724]. The tests verify high-water-mark completion, error handling, API variants, web-stream output, and the callback API's paused return stream. These changes support the linked objective. No unrelated change is shown in the reviewed diff.
Full details: Description check
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Explanation
The pull request description is complete. It explains the problem, the implementation, compatibility considerations, downsides, and verification steps. The Problem and Fix sections provide the information required by “What does this PR do?”, and the Verified section provides the information required by “How did you verify your code works?”.
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Updated 12:38 PM PT - Oct 27th, 2026
✅ @robobun, your commit 2ea61604529dca2267e8a69eab1d17f50c8eff4a passed in 🧪 To try this PR locally: bunx bun-pr 45982That installs a local version of the PR into your bun-45982 --bun |
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Nothing blocking. The comments below are optional suggestions. There is no need to push a fix for them before merging.
LGTM — the inline comments are all nits; the fix itself is small and matches the pipelineImpl contract. Beyond those, I checked that the single-array unwrap in stream.promises.ts runs after the options pop and mirrors pipelineImpl's own streams.length === 1 && ArrayIsArray(streams[0]) check, that pl() always returns the objectMode PassThrough when the tail is a function (so stream.readable is a safe guard, and the then/iterable/web-stream tail branches all end up draining the same pt), and that the pre-aborted-signal and generator-throw paths still reach reject via finishImpl.
Extended reasoning...
The change touches only the promise wrapper in src/js/internal/stream.promises.ts (captures pipelineImpl's return value and calls resume() on it when the last pipeline entry is a function), plus a new describe block in test/js/node/stream/node-stream.test.js and a block appended to the vendored test/js/node/test/parallel/test-stream-pipeline.js. It touches no security-sensitive surface; the ArrayIsArray capture follows the identical pattern already used in src/js/internal/streams/pipeline.ts:24. The production diff is roughly ten lines, the tests exercise every promise entry point plus the callback API's unchanged paused-stream contract, no CODEOWNERS entry covers the changed files, and all surviving findings are style nits rather than correctness issues.
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Actionable comments posted: 1
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Inline comments:
Review comments at @test/js/node/test/parallel/test-stream-pipeline.js:
- Around line 1656-1671: Remove the added passThrough, streams, and pipelinep
test block from the vendored Node.js test suite, leaving coverage in the
existing Bun-owned stream test file unchanged.
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Nothing blocking. The comments below are optional suggestions. There is no need to push a fix for them before merging.
LGTM — the latest commit addresses the earlier nits (intrinsic $isArray, module-scope imports, Buffer.alloc chunk, one-line comment), and the resume() placement in the promise wrapper mirrors the upstream nodejs/node#65559 control flow while leaving the callback API's paused PassThrough contract intact.
Extended reasoning...
The change adds five lines to src/js/internal/stream.promises.ts (capture pipelineImpl's return value, unwrap the single-array form, resume the proxy PassThrough when the tail is a function and the stream is readable) plus nine tests in node-stream.test.js and a vendored block in test-stream-pipeline.js. It touches no security-sensitive surface. I diffed the wrapper against pipelineImpl: the PassThrough proxy is only built for a non-reading function tail, so stream.readable is true for generator, promise and web-ReadableStream returns alike, and the resume is scoped to the promise API so Stream.pipeline(...).pipe() still delivers every chunk (pinned by the new callback test). The remaining inline findings are a pre-existing { end: false } destroy path that Node's identical code shares and a test error-wiring nit, neither of which changes the correctness of the fix; no CODEOWNERS entry covers these files and no third-party objection is outstanding.
…am-promises-pipeline-resume-function-tail # Conflicts: # test/js/node/stream/node-stream.test.js
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LGTM — the latest push resolves the earlier inline notes (vendored Node test restored, sink errors wired through finishedP), and the runtime change is a small, faithful port of nodejs/node#65559.
What was reviewed:
- Traced
pipelineImplfor a function tail:retis always the proxyPassThroughwhether the function returns a promise, an async iterable, or a web stream, sostream.readableis truthy on every path the newresume()is meant to cover; the single-array unwrap mirrors the one atpipeline.ts:167. - Checked that a sync throw from
pl(...)(e.g. ERR_MISSING_ARGS) still rejects via the executor before the resume runs, and that an empty argument list after the options pop cannot reachlastStream[...]. - Confirmed
Stream.promises.pipelineandpromisify(Stream.pipeline)both route to this one function viainternal/stream.ts, so the test's three entry points exercise the same code.
Extended reasoning...
The diff adds five lines to src/js/internal/stream.promises.ts (capture pipelineImpl's return value, compute the last entry including the single-array form, resume the proxy PassThrough when that entry is a function) and a nine-test describe block in test/js/node/stream/node-stream.test.js covering the variadic, array, trailing-options, promisify, error, web-stream, and aborted-signal variants plus the callback API's paused-return contract. It touches no security-sensitive surface. The bug hunt ran dry with no findings, every earlier inline note from this bot was addressed by commits a5a6671 and 485671a (the vendored test edit was dropped entirely, which also moots the coderabbit comment on that file), the changed paths have no CODEOWNER entry, and the runtime logic matches the upstream Node fix it cites.
Still open from earlier reviews (1):
- Unresolved: 1 minor or pre-existing.
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LGTM — the latest pushes address everything raised earlier, and the fix is a small, self-contained port of the upstream change.
What was reviewed:
- The wrapper in src/js/internal/stream.promises.ts:
pl()always returns the proxy PassThrough for a function tail (pipeline.ts:338),$isArrayis the intrinsic used across src/js, and the single-array unwrap runs after the options pop sopipeline([src, fn], opts)is covered. - Callback
Stream.pipelineis untouched, and the new test pins that its returned stream stays paused for a laterpipe(). - Checked the sync-throw path (ERR_MISSING_ARGS etc.) —
pl()throwing inside the executor still rejects as before;stream.resume()is only reached after a successful return. - Tests: module-scope imports,
Buffer.allocchunk, error-wiredfinishedP(sink), plainawaiton the hang-prone promises; the vendored node test is no longer modified.
Extended reasoning...
The diff adds five lines to the node:stream/promises pipeline wrapper to resume the proxy PassThrough when the last entry is a function, plus nine tests in test/js/node/stream/node-stream.test.js covering the generator, single-array, trailing-options, promisify, web-ReadableStream, error, and aborted-signal variants. It touches no security-sensitive surface. The change mirrors the shape of nodejs/node#65559, the callback form is explicitly left unchanged and tested, and each nit from the prior three review rounds is visibly addressed in the code at HEAD. No CODEOWNER covers the changed files, the bug hunt ran dry with no findings, and the only third-party thread was resolved by a non-author on a file that has since been dropped from the diff.
…am-promises-pipeline-resume-function-tail # Conflicts: # test/js/node/stream/node-stream.test.js
Fixes #45724
Problem
require("node:stream/promises").pipeline(Readable.from(100 chunks), async function* (src) { ... })never settles. Ten chunks resolve. Sixteen or more hang.pipelineImpl(src/js/internal/streams/pipeline.ts:301) wraps its output in an object-modePassThroughand pumps the generator into it. The promise wrapper (src/js/internal/stream.promises.ts) dropped the stream thatpipelineImplreturns. Nothing read thePassThrough, so at the high water markwrite()returned false and the pump waited for adrainthat never came.Fix
pipelineImpl. When the last entry is a function (also in the single-array call form) and the stream is readable, it callsstream.resume(). This is a port of stream: fix pipeline function tail deadlock nodejs/node#65559 (fixes pipeline deadlock with readable tail? nodejs/node#40685).PassThrough, sopipeline(...).pipe(dest)on a later tick still delivers every chunk. A new test pins that.test/js/node/stream/node-stream.test.js(9 new tests, 7 time out on bun 1.4.3). Also the vendoredtest-stream-pipeline.js,test-stream-promises.js,test-stream3-pipeline-async-iterator.js,test-stream-pipeline-async-iterator.js,test-webstreams-pipeline.js,test-stream-compose.js.Background
pipelineImplis the shared core of bothstream.pipeline(..., cb)andstream/promises.pipeline(...). For a function tail it returns a proxyPassThroughso callback users can compose it with.pipe(). Node keeps that contract and fixes the promise side only, inlib/stream/promises.js.node:stream/promises,Stream.promises.pipeline,util.promisify(Stream.pipeline)) reach the one function instream.promises.ts, so the fix covers all of them.resume()insidepipelineImplnext to thePassThrough: one line, but it breaks the callback API. A consumer that pipes on the next tick receives 0 of 100 chunks instead of 100.Downsides
PassThrough. Measured with a 10-object generator:process.nextTickcalls 20 to 22,emitcalls 26 to 39. The 100-object path now does exactly what the callback API does with an explicitresume(): 59 ticks, 249 emits. The stream-tail promise path is unchanged: 13 ticks, 12 emits before and after.internal/stream.promises: +273 bytes (1068 to 1341 in the debug bundle). Release binary size not measured withbloaty.Notes
Repro from the issue, on bun 1.4.3:
still pending after 3s, exit 1. On this branch:resolved, exit 0.The new tests use a plain
awaitinstead ofexpect(p).resolves. With a promise that never settles, the.resolvesmatcher spins the event loop and the per-test timeout never fires (#33261). With a plainawaitthe 7 hanging tests time out cleanly on bun 1.4.3.The vendored
test/js/node/test/parallel/test-stream-pipeline.jsis unchanged. The block that nodejs/node#65559 adds there arrives with the next sync of the node suite. A full re-vendor from node main carries three unrelated http hunks, one of which fails on bun today.Counts came from a script that wraps
process.nextTickandEventEmitter.prototype.emitwith counters and runs one pipeline.no test proof · iteration 0 · platform-specific test(s) that do not run on this machine, deferring to CI, which covers all platforms: test/js/node/stream/node-stream.test.js