fix(worker): route worker_threads errors like the web surface, and fire once listeners once

[adrian-niculescu]

A parentPort.on("message") listener that throws never reaches the worker's onerror or the parent's worker.on("error"). The relay dispatched without rethrowing, so the throw went to the uncaught-error reporter and stopped there. It now dispatches the way worker-global message delivery does.

An error that a worker.on("error") listener handled was also reported to the parent's global scope as unhandled, because the Worker's onerror returned nothing. It now returns whether a listener ran, which cancels the event, and the emitter reports that the way Node's emit does.

A once listener could fire twice: when an earlier listener emitted the same event again, the nested emit fired and removed it, and the outer emit then called it a second time from its snapshot. A once registration now records that it fired, as Node's once wrapper does, so a once listener an earlier listener removed still fires, as in Node.

The same fix for Android is NativeScript/android#2065. All three new specs fail on main and pass here, and the full TestRunner suite passes.

Summary by CodeRabbit

• Bug Fixes
  • Worker errors handled by their registered error listeners are no longer also reported to the parent scope’s global error listener.
  • One-time event listeners now run only once, even when an event is emitted again recursively while the listener is running.
  • Errors thrown by message handlers are delivered to the parent worker’s error listener exactly once.

[coderabbitai]

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ℹ️ Recent review info

⚙️ Run configuration

• Configuration used: Repository UI
• Review profile: CHILL
• Plan: Advanced
• Run ID: 28ff14d2-d3cf-4519-99ec-2164703f224c

📥 Commits

Reviewing files that changed from the base of the PR and between 4ae32eb and e823dff.

📒 Files selected for processing (3)

• NativeScript/runtime/js/node-worker-threads.js
• TestRunner/app/tests/MessagingTests.js
• TestRunner/app/tests/messaging/parentPortThrowingWorker.js

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📝 Walkthrough

Walkthrough

Worker event emission now reports whether listeners were registered and prevents a once-listener from firing again during nested emission. Worker-scope error forwarding uses rethrowing dispatch. New regression tests cover these event and error cases.

Changes

Worker event handling

Layer / File(s)	Summary
Emission results and once-listeners NativeScript/runtime/js/node-worker-threads.js, TestRunner/app/tests/MessagingTests.js	WorkerEmitter.emit returns false when no listeners are registered and true after dispatch. Once-listeners are marked fired before invocation. A regression test checks that recursive emission does not invoke a once-listener again.
Worker error forwarding NativeScript/runtime/js/node-worker-threads.js, TestRunner/app/tests/MessagingTests.js, TestRunner/app/tests/messaging/parentPortThrowingWorker.js	The worker error handler returns the result of emitting "error", and the worker-scope relay uses dispatchEventRethrowing. Regression tests check handled worker errors and errors thrown by parentPort message listeners.

Priority: ⬇️ Low

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Bug fix

Suggested reviewers: edusperoni

Merge Risk: ⚪ Minimal · up to e823d

The reviewed worker error and once-listener paths show no actionable merge-blocking issue. Merge after normal checks.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly identifies both main changes: worker error routing and reentrant once-listener behavior.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 3…
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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_{A rabbit taps a message through,
A once-listener runs once, not two.
An error finds its listener’s ear,
The worker sends the signal clear.
Then hops away, with tests in view.}

_{Comment @coderabbitai help to get the list of available commands.}