test: ignore late worker exceptions in WPT runner

[marcopiraccini]

Problem

WPT semantics: once done() is called the test result is final. Browsers send any later exception to window.onerror and do not fail the test. Node's WPT worker forwarded post-completion uncaughtExceptions to the parent as Worker 'error' events, which the runner reports as failures.

Affected flaky tests:

• wpt/test-timers → html/webappapis/timers/type-long-settimeout.any.js
• wpt/test-timers → html/webappapis/timers/type-long-setinterval.any.js

Fix

Install a no-op uncaughtException handler from inside add_completion_callback, before posting completion. Late exceptions in the worker are then swallowed, matching browser semantics. Scope is one fixture per worker (one Worker per spec), so it cannot leak into other tests.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.33%. Comparing base (e2ad744) to head (c6751d8).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #63106      +/-   ##
==========================================
+ Coverage   90.31%   90.33%   +0.02%     
==========================================
  Files         730      730              
  Lines      234463   234463              
  Branches    43908    43916       +8     
==========================================
+ Hits       211763   211812      +49     
+ Misses      14419    14374      -45     
+ Partials     8281     8277       -4     

see 35 files with indirect coverage changes

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[panva]

You might want to update test/wpt/status/web-locks.json which has an expected uncaught rejection marked as flaky.

[panva]

matching browser semantics

Can you elaborate? Is this rooted in the WPT runner browsers run, generally more context for review would be great.

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/73662/

[marcopiraccini]

matching browser semantics

Can you elaborate? Is this rooted in the WPT runner browsers run, generally more context for review would be great.

It's actually WPT semantic. In resources/testharness.js. The global error handler ignores exceptions once a test has a result (phase >= HAS_RESULT).
Our worker instead forwards a post-done() uncaughtException as a Worker 'error' event.

I think WPT is mirroring the browser's beaviour where the uncaugth exceptions after done are non-fatal

Editing the description and the comment.

[marcopiraccini]

You might want to update test/wpt/status/web-locks.json which has an expected uncaught rejection marked as flaky.

Maybe I am missing something, but I don't think this change covers it. It seems held.https.any.js sets allow_uncaught_exception: true and rejects during the test, not after done().
The handler here is installed in add_completion_callback, so it only covers post-completion exceptions and won't reach that rejection.