Fix "Cannot read property 'name' of undefined" when Promise is rejected without a reason

[Copilot]

When Promise.reject() is called without an argument, onunhandledrejection fires with e.reason as undefined/null. Passing this to computeStackTrace causes a crash in the final fallback return where ex.name and ex.message are accessed unconditionally.

Changes

• tracekit.js: Guard property access in the computeStackTrace fallback return using short-circuit evaluation:

  // Before
  return { 'name': ex.name, 'message': ex.message, 'mode': 'failed' };
  
  // After
  return { 'name': ex && ex.name, 'message': ex && ex.message, 'mode': 'failed' };

• spec/tracekit-spec.js: Add tests covering computeStackTrace(undefined) and computeStackTrace(null) to prevent regression.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• accounts.google.com
  • Triggering command: /proc/self/exe /proc/self/exe --type=utility --utility-sub-type=network.mojom.NetworkService --lang=en-US --service-sandbox-type=none --no-sandbox --disable-dev-shm-usage --use-angle=swiftshader-webgl --crashpad-handler-pid=3926 --enable-crash-reporter=, --noerrdialogs --user-data-dir=/tmp/karma-79623365 --change-stack-guard-on-fork=enable --shared-files=v8_context_snapshot_data:100 --field-trial-handle=3,i,7964489220704497771,8279194133401378956,262144 --disable-features=PaintHolding --variations-seed-version --trace-process-track-uuid=3190708989122997041 (dns block)
  • Triggering command: /opt/google/chrome/chrome /usr/bin/google-chrome --user-data-dir=/tmp/karma-79623365 --enable-automation --no-default-browser-check --no-first-run --disable-default-apps --disable-popup-blocking --disable-translate --disable-REDACTED-timer-throttling --disable-renderer-REDACTEDing --disable-device-discovery-notifications --no-sandbox --disable-gpu http://localhost:9876/?id=79623365 --headless --disable-gpu --disable-dev-shm-usage --remote-debugging-port=9222 (dns block)
• clients2.google.com
  • Triggering command: /proc/self/exe /proc/self/exe --type=utility --utility-sub-type=network.mojom.NetworkService --lang=en-US --service-sandbox-type=none --no-sandbox --disable-dev-shm-usage --use-angle=swiftshader-webgl --crashpad-handler-pid=3926 --enable-crash-reporter=, --noerrdialogs --user-data-dir=/tmp/karma-79623365 --change-stack-guard-on-fork=enable --shared-files=v8_context_snapshot_data:100 --field-trial-handle=3,i,7964489220704497771,8279194133401378956,262144 --disable-features=PaintHolding --variations-seed-version --trace-process-track-uuid=3190708989122997041 (dns block)
  • Triggering command: /opt/google/chrome/chrome /usr/bin/google-chrome --user-data-dir=/tmp/karma-79623365 --enable-automation --no-default-browser-check --no-first-run --disable-default-apps --disable-popup-blocking --disable-translate --disable-REDACTED-timer-throttling --disable-renderer-REDACTEDing --disable-device-discovery-notifications --no-sandbox --disable-gpu http://localhost:9876/?id=79623365 --headless --disable-gpu --disable-dev-shm-usage --remote-debugging-port=9222 (dns block)
• clientservices.googleapis.com
  • Triggering command: /proc/self/exe /proc/self/exe --type=utility --utility-sub-type=network.mojom.NetworkService --lang=en-US --service-sandbox-type=none --no-sandbox --disable-dev-shm-usage --use-angle=swiftshader-webgl --crashpad-handler-pid=3926 --enable-crash-reporter=, --noerrdialogs --user-data-dir=/tmp/karma-79623365 --change-stack-guard-on-fork=enable --shared-files=v8_context_snapshot_data:100 --field-trial-handle=3,i,7964489220704497771,8279194133401378956,262144 --disable-features=PaintHolding --variations-seed-version --trace-process-track-uuid=3190708989122997041 (dns block)
  • Triggering command: /opt/google/chrome/chrome /usr/bin/google-chrome --user-data-dir=/tmp/karma-79623365 --enable-automation --no-default-browser-check --no-first-run --disable-default-apps --disable-popup-blocking --disable-translate --disable-REDACTED-timer-throttling --disable-renderer-REDACTEDing --disable-device-discovery-notifications --no-sandbox --disable-gpu http://localhost:9876/?id=79623365 --headless --disable-gpu --disable-dev-shm-usage --remote-debugging-port=9222 (dns block)
• redirector.gvt1.com
  • Triggering command: /proc/self/exe /proc/self/exe --type=utility --utility-sub-type=network.mojom.NetworkService --lang=en-US --service-sandbox-type=none --no-sandbox --disable-dev-shm-usage --use-angle=swiftshader-webgl --crashpad-handler-pid=3926 --enable-crash-reporter=, --noerrdialogs --user-data-dir=/tmp/karma-79623365 --change-stack-guard-on-fork=enable --shared-files=v8_context_snapshot_data:100 --field-trial-handle=3,i,7964489220704497771,8279194133401378956,262144 --disable-features=PaintHolding --variations-seed-version --trace-process-track-uuid=3190708989122997041 (dns block)
  • Triggering command: /opt/google/chrome/chrome /usr/bin/google-chrome --user-data-dir=/tmp/karma-79623365 --enable-automation --no-default-browser-check --no-first-run --disable-default-apps --disable-popup-blocking --disable-translate --disable-REDACTED-timer-throttling --disable-renderer-REDACTEDing --disable-device-discovery-notifications --no-sandbox --disable-gpu http://localhost:9876/?id=79623365 --headless --disable-gpu --disable-dev-shm-usage --remote-debugging-port=9222 (dns block)
• safebrowsingohttpgateway.googleapis.com
  • Triggering command: /proc/self/exe /proc/self/exe --type=utility --utility-sub-type=network.mojom.NetworkService --lang=en-US --service-sandbox-type=none --no-sandbox --disable-dev-shm-usage --use-angle=swiftshader-webgl --crashpad-handler-pid=3926 --enable-crash-reporter=, --noerrdialogs --user-data-dir=/tmp/karma-79623365 --change-stack-guard-on-fork=enable --shared-files=v8_context_snapshot_data:100 --field-trial-handle=3,i,7964489220704497771,8279194133401378956,262144 --disable-features=PaintHolding --variations-seed-version --trace-process-track-uuid=3190708989122997041 (dns block)
  • Triggering command: /opt/google/chrome/chrome /usr/bin/google-chrome --user-data-dir=/tmp/karma-79623365 --enable-automation --no-default-browser-check --no-first-run --disable-default-apps --disable-popup-blocking --disable-translate --disable-REDACTED-timer-throttling --disable-renderer-REDACTEDing --disable-device-discovery-notifications --no-sandbox --disable-gpu http://localhost:9876/?id=79623365 --headless --disable-gpu --disable-dev-shm-usage --remote-debugging-port=9222 (dns block)
• www.google.com
  • Triggering command: /proc/self/exe /proc/self/exe --type=utility --utility-sub-type=network.mojom.NetworkService --lang=en-US --service-sandbox-type=none --no-sandbox --disable-dev-shm-usage --use-angle=swiftshader-webgl --crashpad-handler-pid=3926 --enable-crash-reporter=, --noerrdialogs --user-data-dir=/tmp/karma-79623365 --change-stack-guard-on-fork=enable --shared-files=v8_context_snapshot_data:100 --field-trial-handle=3,i,7964489220704497771,8279194133401378956,262144 --disable-features=PaintHolding --variations-seed-version --trace-process-track-uuid=3190708989122997041 (dns block)
  • Triggering command: /opt/google/chrome/chrome /usr/bin/google-chrome --user-data-dir=/tmp/karma-79623365 --enable-automation --no-default-browser-check --no-first-run --disable-default-apps --disable-popup-blocking --disable-translate --disable-REDACTED-timer-throttling --disable-renderer-REDACTEDing --disable-device-discovery-notifications --no-sandbox --disable-gpu http://localhost:9876/?id=79623365 --headless --disable-gpu --disable-dev-shm-usage --remote-debugging-port=9222 (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Cannot read property 'name' of undefined</issue_title>
<issue_description>I've got an error like in title. It's in function computeStackTrace in last return when tries to get ex.name.

It is called by function traceKitWindowOnUnhandledRejection (and I don't have more stacktrace).

Could you tell me why I got this error? </issue_description>

<agent_instructions>Make sure we have test coverage and can reproduce before fixing. make sure you look at the linked pr and also make sure you look at how the fix in their main branch has changed any. If the code has been replaced, look at what it looked like right before they replaced (if they are no longer using tracekit)</agent_instructions>

Comments on the Issue (you are @copilot in this section)

@niemyjski This is a function that is wired up to https://developer.mozilla.org/en-US/docs/Web/API/WindowEventHandlers/onunhandledrejection and handles this type of event. Sounds like that event can be null. Can you let us know how you reproduced it and with the specifics of what browser/os you were using with specific versions.

• Fixes Cannot read property 'name' of undefined #86

---

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[liviuconcioiu]

Change looks good. Thank you for the fix. If a new version can be released, that will be awesome!

[niemyjski]

Pushed