test_runner: avoid hanging on incomplete v8 frames by thisalihassan · Pull Request #62704 · nodejs/node

thisalihassan · 2026-04-12T10:23:12Z

The test runner could hang while draining child stdout when the buffered data started with bytes that matched the V8 serializer header (0xff 0x0f) but did not contain a complete serialized frame.

In that case #processRawBuffer() made no progress, and #drainRawBuffer() kept calling it in a loop forever.

This change makes the deserializer recover from that end-of-stream case by flushing the buffered bytes as stdout and continuing to resync. It also preserves the ordering of a trailing partial V8 header split across chunks.

Closes #62693

Assisted-by: Claude Opus

nodejs-github-bot · 2026-04-12T10:23:19Z

Review requested:

@nodejs/test_runner

aduh95 · 2026-04-12T10:41:24Z

+    // size, causing #processRawBuffer to make no progress and
+    // #drainRawBuffer to loop forever without the no-progress guard.
+    const reported = await collectReported([oversizedLengthHeader]);
+    assert(reported.every((event) => event.type === 'test:stdout'));


We can get a much more useful error output by using partialDeepStrictEqual here

Suggested change

assert(reported.every((event) => event.type === 'test:stdout'));

assert.partialDeepStrictEqual(reported, Array.from({ length: reported.length }, () => ({ type: 'test:stdout' }));

aduh95 · 2026-04-12T10:45:44Z

+          data: {
+            __proto__: null,
+            file: this.name,
+            message: TypedArrayPrototypeSubarray(bufferHead, 0, 1).toString('utf-8'),


If we're dealing with a single-byte UTF-8 char, we don't need the intermediate view I think

Suggested change

message: TypedArrayPrototypeSubarray(bufferHead, 0, 1).toString('utf-8'),

message: StringFromCharCode(bufferHead[0]),

it changes the output semantics here StringFromCharCode(0xff) gives "ÿ" but Buffer.from([0xff]).toString('utf8') gives "�" which matches the current stdout path so I’m keeping the UTF-8 decode

String.fromCodePoint then – but I'm surprised we would get non-ASCII chars here

Right, switched to StringFromCharCode the byte here is always the V8 version tag (0xFF)

Signed-off-by: Ali Hassan <ali-hassan27@outlook.com>

avivkeller · 2026-04-12T12:14:19Z

Can you add a proper PR description?

codecov · 2026-04-12T12:39:32Z

Codecov Report

❌ Patch coverage is 95.65217% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.80%. Comparing base (0fea430) to head (e07cdd4).
⚠️ Report is 355 commits behind head on main.

Files with missing lines	Patch %	Lines
lib/internal/test_runner/runner.js	95.65%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #62704      +/-   ##
==========================================
- Coverage   89.80%   89.80%   -0.01%     
==========================================
  Files         699      699              
  Lines      216363   216417      +54     
  Branches    41370    41377       +7     
==========================================
+ Hits       194309   194356      +47     
- Misses      14140    14141       +1     
- Partials     7914     7920       +6

Files with missing lines	Coverage Δ
lib/internal/test_runner/runner.js	`93.68% <95.65%> (+0.03%)`	⬆️

... and 34 files with indirect coverage changes

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…-byte fallback path Signed-off-by: Ali Hassan <ali-hassan27@outlook.com>

thisalihassan · 2026-04-30T13:55:48Z

@aduh95 can you please take a relook at this again?

nodejs-github-bot · 2026-05-17T21:10:13Z

CI: https://ci.nodejs.org/job/node-test-pull-request/73512/

nodejs-github-bot · 2026-05-18T07:54:37Z

Landed in debe2ed

Signed-off-by: Ali Hassan <ali-hassan27@outlook.com> PR-URL: #62704 Reviewed-By: Moshe Atlow <moshe@atlow.co.il> Reviewed-By: Chemi Atlow <chemi@atlow.co.il>

nodejs-github-bot added needs-ci PRs that need a full CI run. test_runner Issues and PRs related to the test runner subsystem. labels Apr 12, 2026

aduh95 reviewed Apr 12, 2026

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test_runner: avoid hanging on incomplete v8 frames

825b3e3

Signed-off-by: Ali Hassan <ali-hassan27@outlook.com>

thisalihassan force-pushed the fix/test-runner-hangs branch from 631f70a to 825b3e3 Compare April 12, 2026 11:20

thisalihassan requested a review from aduh95 April 12, 2026 11:21

Replace TypedArrayPrototypeSubarray StringFromCharCode in the byte-by…

e07cdd4

…-byte fallback path Signed-off-by: Ali Hassan <ali-hassan27@outlook.com>

MoLow approved these changes Apr 13, 2026

View reviewed changes

atlowChemi approved these changes Apr 30, 2026

View reviewed changes

atlowChemi mentioned this pull request May 5, 2026

test_runner: prevent infinite loop on malformed v8 header #63124

Closed

panva added the request-ci Add this label to start a Jenkins CI on a PR. label May 17, 2026

github-actions Bot removed the request-ci Add this label to start a Jenkins CI on a PR. label May 17, 2026

atlowChemi added commit-queue Add this label to land a pull request using GitHub Actions. commit-queue-squash Add this label to instruct the Commit Queue to squash all the PR commits into the first one. labels May 18, 2026

nodejs-github-bot removed the commit-queue Add this label to land a pull request using GitHub Actions. label May 18, 2026

nodejs-github-bot merged commit debe2ed into nodejs:main May 18, 2026
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aduh95 pushed a commit that referenced this pull request May 19, 2026

test_runner: avoid hanging on incomplete v8 frames

1dfa82a

Signed-off-by: Ali Hassan <ali-hassan27@outlook.com> PR-URL: #62704 Reviewed-By: Moshe Atlow <moshe@atlow.co.il> Reviewed-By: Chemi Atlow <chemi@atlow.co.il>

aduh95 pushed a commit that referenced this pull request May 19, 2026

test_runner: avoid hanging on incomplete v8 frames

83054e8

Signed-off-by: Ali Hassan <ali-hassan27@outlook.com> PR-URL: #62704 Reviewed-By: Moshe Atlow <moshe@atlow.co.il> Reviewed-By: Chemi Atlow <chemi@atlow.co.il>

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test_runner: avoid hanging on incomplete v8 frames#62704

test_runner: avoid hanging on incomplete v8 frames#62704
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	assert(reported.every((event) => event.type === 'test:stdout'));
	assert.partialDeepStrictEqual(reported, Array.from({ length: reported.length }, () => ({ type: 'test:stdout' }));

	message: TypedArrayPrototypeSubarray(bufferHead, 0, 1).toString('utf-8'),
	message: StringFromCharCode(bufferHead[0]),

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