node:stream: Readable.fromWeb emits an AbortError when the web stream fails with a falsy value by robobun · Pull Request #43732 · oven-sh/bun

robobun · 2026-09-22T00:47:04Z

Problem

Readable.fromWeb(stream) emits 'close' with neither 'end' nor 'error' when the web stream fails with a falsy value: controller.error(null), or controller.abort(null) on a fetch() body. A promise that waits for 'end' or 'error' never settles. Node v26.3.0 emits 'error' with an AbortError (code: "ABORT_ERR").
Cause: destroy(null) means no error. ReadableFromWeb.#handleError (src/js/internal/webstreams_adapters.ts:85) called this.destroy(error), and read() (src/js/internal/streams/native-readable.ts) gave a falsy pull failure to errorOrDestroy().

Fix

#handleError calls destroyer(this, error), as Node's adapter does. destroyer() replaces a falsy error with an AbortError.
read() sends a rejected or throwing pull() to failPull(), which passes reason || $makeAbortError() on. A truthy reason is unchanged.
Verified: 8 new cases in test/js/node/stream/node-stream.test.js and 6 in test/js/web/fetch/fetch-abort-stream-body.test.ts. All 14 fail on main. Other suites: see Notes.

Background

Readable.fromWeb returns a NativeReadable for a stream with a native source (a fetch body, a file), and a ReadableFromWeb for every other stream.
Considered replacing a falsy abort reason in fetch(), as undici does: user streams stay broken. Both adapters see every web stream failure.

Downsides

A program with no 'error' listener got a quiet 'close'. It now ends with an uncaught AbortError (exit code 1), as in Node.
for await, pipeline() and finished() now report the AbortError where they reported ERR_STREAM_PREMATURE_CLOSE, as in Node. For a fetch() body Node's code is 20 (a DOMException), not "ABORT_ERR".
Cost: +153 bytes of built-in JS and one jmp bytecode more per native read(). No new allocation.

Notes

Repro

import { Readable } from "node:stream";
for (const reason of [null, 0, ""]) {
  const readable = Readable.fromWeb(new ReadableStream({ start(c) { c.error(reason); } }));
  const seen = [];
  readable.on("error", e => seen.push(`error(${e.name})`)).on("end", () => seen.push("end"));
  readable.on("close", () => console.log(String(reason), seen.join(","), "close"));
  readable.resume();
}
// node v26.3.0: error(AbortError) close        bun main: close

The two paths

The throwing pull(): a native source that already holds its error throws it from pull(), and Readable hands what _read() throws to errorOrDestroy() as is. Repro: Readable.fromWeb(new HTMLRewriter().transform(new Response(input)).body) after input was errored with null. The review found this twin of the rejection path. Its 4 test cases fail on the first head of this PR.
With fetch(): node answers abort(null) with an AbortError for every body reader, because undici replaces a falsy reason at the fetch level. Bun keeps the reason (await res.text() rejects with null), which is what the Fetch spec describes. This PR does not change that.
destroyer() replaces a falsy error only while the stream is not finished (!err && !isFinished(stream), src/js/internal/streams/destroy.ts:306).

fetch() bodies: when controller.abort(null) arrives

timing	1.4.3-canary (`367d939`, before #43699)	main `179664e`	this PR
before `Readable.fromWeb(res.body)`	`'close'`	`'close'`	`'error'` (`AbortError`), `'close'`
one tick after the first `'data'`	`'end'`, `'close'`	`'close'`	`'error'` (`AbortError`), `'close'`
after `fromWeb()`, before the first read	`'end'`, `'close'`	`'error'` (`DOMException`, `code: 20`), `'close'`	the same as main

Before fetch: fail a native reader of an aborted res.body with signal.reason #43699 the second and third rows ended as if the body were complete. fetch: fail a native reader of an aborted res.body with signal.reason #43699 made the second row fail with the reason, and a falsy reason then gave 'close' alone.
The third row does not pass through this change. Nothing waits for the reason there, and the native source fails with its own DOMException for every reason.

What moves for a program

One process per row, on main 179664e, on this PR merged with that main (debug builds, Linux x64), and on Node v26.3.0.

Sources: a web stream whose pull() calls controller.error(v). An HTMLRewriter output whose input failed with v. A fetch() body with controller.abort(v) before Readable.fromWeb(). The same with the abort 250 ms after the consumer starts.
Values: undefined, null, 0, "", false, and new Error("x") as the control.

consumer	main	this PR	rows
`resume()`, no `'error'` listener	`'close'`, exit code 0	uncaught `AbortError`, exit code 1	18
`pipe(dest)`, no `'error'` listener	`'close'`, exit code 0	uncaught `AbortError`, exit code 1	18
a promise on `'end'` and `'error'`	never settles	rejects with the `AbortError`	18
`for await`	throws `ERR_STREAM_PREMATURE_CLOSE`	throws the `AbortError`	18
`pipeline()`	callback gets `ERR_STREAM_PREMATURE_CLOSE`	callback gets the `AbortError`	18
`finished()`	callback gets `ERR_STREAM_PREMATURE_CLOSE`	callback gets the `AbortError`	18

Bun has 144 rows. 108 move, as the table shows. 36 do not move: the 24 control rows, and the 12 fetch() rows with abort(undefined). abort(undefined) is abort(), and its default reason is a DOMException, which is not falsy.
Node has 108 of these rows (it has no HTMLRewriter). No row is equal to Node on main and different with this PR. 30 rows move to Node's answer. 48 rows, all fetch() bodies, move to an AbortError with code: "ABORT_ERR" where Node has a DOMException with code: 20. 26 rows are equal to Node before and after.
The last 4 rows differ from Node before and after: abort() on a fetch() body with no 'error' listener. Node throws the DOMException. Bun throws an ERR_UNHANDLED_ERROR, because Error.isError(new DOMException()) is false in Bun and node:events tests that. This PR does not touch it. node:events, node:assert: throw the error itself when it inherits from Error.prototype #45255 changes that test in node:events, and DOMException: inherit from ErrorInstance for [[ErrorData]] and .stack #32898 makes a DOMException an error for Error.isError.

Costs

Size: the production bundle of src/js (bundle-modules.ts --debug=OFF, InternalModuleRegistryConstants.bin) is 2,714,593 bytes on main and 2,714,746 bytes with this PR. internal/streams/native-readable.js grows by 150 bytes and internal/webstreams_adapters.js by 3.
Per call: the bytecode of read() (BUN_JSC_dumpGeneratedBytecodes=1, debug build) has 216 instructions on main and 226 with this PR. 9 of the 10 run only when pull() throws. The path that does not throw runs one more jmp, over the catch block. A pending pull makes 2 closures in both versions.
ReadableFromWeb: destroyer() runs only when the web stream fails. The path with no failure is the same code.
There is no instruction count. perf and valgrind are not in my container.

Suites

On this PR merged with main 179664e (debug build, Linux x64): node-stream.test.js 126 pass, fetch-abort-stream-body.test.ts 81 pass, web-stream-state.test.ts 46 pass, node-stream-uint8array.test.ts 5 pass, test/js/web/streams/streams.test.js 727 pass. The 23 files in test/js/node/test/parallel with webstreams, readable-from-web or toWeb in the name pass.
With the src/ of main, the 14 new cases fail and the other 193 cases of the two files pass.
child_process.test.ts: 83 pass and 2 fail, with and without this change. The 2 are "extra stdio pipes are not double-closed on GC" and "spawn still works with more than 10240 fds open" (my container allows 1024 open files).

no test proof · iteration 4 · platform-specific test(s) that do not run on this machine, deferring to CI, which covers all platforms: test/js/web/fetch/fetch-abort-stream-body.test.ts, test/js/node/stream/node-stream.test.js

… fails with a falsy value destroy(null) emits 'close' alone, so a node stream cannot carry a falsy error. Node's adapter destroys through destroyer(), which makes an AbortError of a falsy error while the stream is unfinished. Bun's adapter called this.destroy(error), and the native readable passed the falsy rejection of a pull to errorOrDestroy(), so the stream closed with neither 'end' nor 'error'. Reachable with a web stream that errors with null, 0 or "", and with a fetch() body whose signal aborts with such a reason.

robobun · 2026-09-22T00:47:16Z

^{Updated 3:23 AM PT - Oct 28th, 2026}

❌ @robobun, your commit fd11f1d has 3 failures in Build #134280 (All Failures):

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🧪 To try this PR locally:

bunx bun-pr 43732

That installs a local version of the PR into your bun-43732 executable, so you can run:

bun-43732 --bun

robobun · 2026-09-22T00:47:25Z

Status: ready for review. The branch is merged with main 11c3671.

CI: build 134280 finished red. No test that this PR touches failed.

116 of 204 jobs passed. 86 jobs were canceled before they started, because the CI could not create their machines (EC2 CapacityLimitExceeded, 05:03 to 05:12 UTC on Oct 28, 8 builds). Those jobs need a re-run.
The canceled jobs are all Linux jobs: the 40 test jobs of debian 13 aarch64 and ubuntu 25.04 aarch64, 32 of the 60 test jobs of debian 13 x64, debian 13 x64-asan and ubuntu 25.04 x64, and 14 jobs of the AOT and baseline lanes.
test/js/node/stream/node-stream.test.js passed (0 fail) on debian 13 x64-asan, ubuntu 25.04 x64, alpine 3.23 x64 and aarch64, Windows 2019 x64, Windows 11 aarch64, macOS x64 and macOS aarch64.
test/js/web/fetch/fetch-abort-stream-body.test.ts passed (0 fail) on debian 13 x64, ubuntu 25.04 x64, alpine 3.23 x64 and aarch64, Windows 2019 x64, Windows 11 aarch64, macOS x64 and macOS aarch64.
The head before this one, 624c32c, passed all 181 jobs of build 132838 on Oct 26. The change of this PR is the same at both heads, except for the type cast of fd11f1d. Between the two heads the branch merged main 11c3671.
test/aot/perf/generated-code-of-idioms-3.test.ts and generated-code-of-idioms-13.test.ts failed on the test-aot-drawn lanes, which do not fail the build. Tests of that family also fail on main (builds 134067 and 134092).

How it was reproduced. Readable.fromWeb(new ReadableStream({ start(c) { c.error(null); } })), with listeners for 'error', 'end' and 'close', then resume().

bun main (179664e, debug build): 'close' only, for null, undefined, 0, "" and false.
Node v26.3.0: 'error' with an AbortError (code: "ABORT_ERR"), then 'close'.
The same through fetch(): controller.abort(null) while Readable.fromWeb(res.body) waits for more body gives 'close' only on main.
A native source that already holds the falsy error throws it from pull(): Readable.fromWeb(new HTMLRewriter().transform(new Response(input)).body) after input was errored with null also gives 'close' only on main.
This PR: 'error' with an AbortError, then 'close', in all of these.

The tests are in test/js/node/stream/node-stream.test.js (8 new cases) and test/js/web/fetch/fetch-abort-stream-body.test.ts (6 new cases). All 14 fail on main 179664e and pass on this branch.

With no 'error' listener on the stream, a program that got a quiet 'close' gets an uncaught AbortError, as in Node. The PR body lists this under Downsides.

coderabbitai · 2026-09-22T00:50:58Z

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Walkthrough

The change normalizes falsy native and web stream rejection reasons to AbortError. It updates web stream destruction handling and adds Node stream and fetch stream regression tests.

Changes

Stream error handling

Layer / File(s)	Summary
Normalize stream errors `src/js/internal/streams/native-readable.ts`, `src/js/internal/webstreams_adapters.ts`	Native pull failures now preserve truthy reasons and use `AbortError` for falsy reasons. Synchronous and asynchronous failures use the same path. `ReadableFromWeb.#handleError` now calls `destroyer`.
Validate falsy error behavior `test/js/node/stream/node-stream.test.js`, `test/js/web/fetch/fetch-abort-stream-body.test.ts`	Tests cover falsy web-stream and fetch-abort reasons. They verify `AbortError`, `ABORT_ERR`, destroyed streams, and the absence of normal completion.

Suggested reviewers: cirospaciari

Priority: Low

Merge Risk: Minimal · previous review 6c3ee

The stream error handling update is ready to merge with no identified blocking risk.

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In `@test/js/node/stream/node-stream.test.js`:
- Line 481: Replace the parameterized it.each() at
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claude

Nothing blocking. The comments below are optional suggestions. There is no need to push a fix for them before merging.

Beyond the inline finding, I also checked that destroyer is already imported in src/js/internal/webstreams_adapters.ts (line 14) and that for a truthy error it reduces to stream.destroy(err) behind the same already-destroyed early return destroy() itself has, so the truthy-error path of ReadableFromWeb is unchanged. The once(readable, "data") + single setImmediate step in the new fetch cases copies the pre-existing sibling test at line 382 of the same file rather than introducing a new timed wait.

Extended reasoning...

The change is two one-line edits in built-in stream adapters (webstreams_adapters.ts, native-readable.ts) that substitute an AbortError for a falsy web-stream error reason, plus parameterized tests in the existing node-stream and fetch-abort test files. It touches no security-sensitive surface. Findings were reported inline, and one verified finding was not posted, so approval is not appropriate; this note only records what else was examined.

claude

Nothing blocking. The comments below are optional suggestions. There is no need to push a fix for them before merging.

…web-falsy-error

…rtError A source that already holds its error throws it from pull() instead of rejecting the pull promise. Readable's catch around _read() gave that falsy value to errorOrDestroy() unchanged, so the stream closed with no 'error'. Both paths now go through one helper. Reachable with the output of an HTMLRewriter whose input failed with null before Readable.fromWeb() pulls.

claude

Nothing blocking. The comments below are optional suggestions. There is no need to push a fix for them before merging.

LGTM — the latest push routes the synchronous ptr.pull() throw through the same failPull helper as the async rejection, so the native-source path I raised earlier is now covered, and both adapters match Node's destroyer() semantics for a falsy reason.

Extended reasoning...

The change is two small edits to bundled node:stream builtins: ReadableFromWeb.#handleError now calls destroyer(this, error) (already imported at src/js/internal/webstreams_adapters.ts:14) instead of this.destroy(error), and src/js/internal/streams/native-readable.ts adds a failPull helper that substitutes $makeAbortError() for a falsy reason on both the sync-throw and promise-rejection paths of ptr.pull(). The sync try/catch preserves prior behavior for truthy errors because readable.ts:665-669 already caught _read throws with errorOrDestroy; destroyer early-returns on an already-destroyed stream just as destroy() did. No security-sensitive surface is touched and no CODEOWNERS entry covers the changed files. Ten new tests cover the plain adapter, a native HTMLRewriter source, and fetch aborts before and during reading; the only remaining finding is a coverage nit (undefined missing from the native matrix).

claude

LGTM — the three follow-up commits address everything raised in earlier rounds, and the change is small and self-contained.

What was reviewed:

ReadableFromWeb.#handleError now routes through destroyer() (already imported), which only differs from this.destroy(error) by substituting an AbortError for a falsy reason on an unfinished stream; the request/socket branches in destroyer do not apply to this class.
In native-readable.ts, wrapping ptr.pull() in try/catch is behavior-preserving for truthy throws: readable.ts:668 already handed them to errorOrDestroy, and the early return happens before kPendingRead is set, so no pending-read state is left dangling.
Tests cover all four falsy values on both the plain adapter and the native (HTMLRewriter) path, plus the fetch matrix asserting name and code; once(readable, "data") rejects on 'error', so the wait is wired to fail rather than hang.

Extended reasoning...

The diff touches two built-in stream modules under src/js/internal (a one-line call swap in webstreams_adapters.ts and a small failPull helper plus try/catch in native-readable.ts) and adds tests to the two existing files that cover these paths. It touches no security-sensitive surface; it only changes which error object a node:stream Readable emits when the underlying web stream fails with a falsy value, matching Node's adapter. The synchronous-throw path was verified equivalent to the previous readable.ts catch for truthy errors, and destroyer()'s extra branches were checked not to apply to ReadableFromWeb. The bug hunt ran dry with no findings, every prior inline comment from this bot was followed by a commit that made the requested change, the CodeRabbit thread was resolved by a non-author, and no CODEOWNERS entry covers the changed paths.

…web-falsy-error

claude

Code review found no issues

No high-confidence issues detected in this change.

…web-falsy-error

Main now types errorOrDestroy() (8d5672c): `err` is `Error | null | undefined`. `reason || $makeAbortError()` with an `unknown` reason is `{}`, so `bun src/codegen/check-types-of-modules.ts` reports TS2345. The reason is cast as readable.ts does for a caught value. What runs does not change.

robobun · 2026-10-28T05:03:06Z

Merged main (11c3671) into this branch. The merge has no conflict and the tree builds, but the type check of src/js in lint.yml then fails:

src/js/internal/streams/native-readable.ts(131,26): error TS2345: Argument of type '{}' is not assignable to parameter of type 'Error'.

Main gave errorOrDestroy types in 8d5672c (Compile TypeScript to machine code ahead of time: bun build --compile --aot #45631): err is Error | null | undefined (src/js/internal/streams/destroy.ts:263). This PR calls it with reason || $makeAbortError(), and reason is unknown.
Commit fd11f1d writes (reason as Error) || $makeAbortError(). That is the only edit. readable.ts:662 casts a caught value the same way. What runs does not change.
bun src/codegen/check-types-of-modules.ts reports that one error on the merged tree without the edit, and none with it. The run had the generated types and the sources of the engine in place, as lint.yml has.
Tests, on a local debug build (Linux x64) that contains this merge and the main merges of seven other open PRs:
- test/js/node/stream/node-stream.test.js: 126 pass, 1 skip, 5 todo.
- test/js/web/fetch/fetch-abort-stream-body.test.ts: 80 pass, with the 6 cases of this PR among them. One older case, which only runs with AddressSanitizer (piping an erroring upstream body into fetch does not double-release the tasklet), reaches the 5 s limit on this debug build. Its fixture prints done 100 and exits 0 in 5.2 s when run by hand.

claude

Code review found no issues

No high-confidence issues detected in this change.

robobun · 2026-10-28T08:52:57Z

About the red CI on fd11f1d: build 134280 did not run the Linux test steps. The agents of nine steps were not created, test-aot and test-bun on Debian 13 among them:

Failed to create agent for :debian: 13 x64 - test-aot
Error: [fetch] POST https://ec2.us-east-1.amazonaws.com/: 400 Bad Request
<Code>CapacityLimitExceeded</Code>

No step of that build failed on a test of this PR. The other red entries passed on a retry, or are in test-aot-drawn, which does not hold up a merge.
Builds that started after 05:23 UTC on the same day got their agents. This build needs a re-run of its failed steps before its result says anything about this PR.

robobun assigned Jarred-Sumner Sep 22, 2026

github-actions Bot added the claude label Sep 22, 2026

coderabbitai Bot reviewed Sep 22, 2026

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Comment thread test/js/node/stream/node-stream.test.js Resolved

ci: retrigger

2e6412d

claude Bot reviewed Sep 22, 2026

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Comment thread test/js/web/fetch/fetch-abort-stream-body.test.ts Resolved

Assert the name and the code of the AbortError in the fetch cases

46188c7

claude Bot reviewed Sep 22, 2026

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Comment thread src/js/internal/streams/native-readable.ts Resolved

robobun added 2 commits September 22, 2026 04:48

Merge remote-tracking branch 'origin/main' into robobun/cc819c75/from…

fc9392c

…web-falsy-error

claude Bot reviewed Sep 22, 2026

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Comment thread test/js/node/stream/node-stream.test.js Resolved

Cover undefined in the native stream cases too

6c3ee09

claude Bot reviewed Sep 22, 2026

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robobun mentioned this pull request Oct 1, 2026

ByteStream: hold a pending JS error in a visited slot instead of a Strong #43410

Open

robobun mentioned this pull request Oct 23, 2026

node:stream: take the native handle in Readable.fromWeb only from a stream no consumer has started #42281

Closed

Merge remote-tracking branch 'origin/main' into robobun/cc819c75/from…

624c32c

…web-falsy-error

claude Bot reviewed Oct 25, 2026

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robobun added 2 commits October 28, 2026 04:06

Merge remote-tracking branch 'origin/main' into robobun/cc819c75/from…

4aa4849

…web-falsy-error

claude Bot reviewed Oct 28, 2026

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