fix error events not working

[robin-drexler]

In polyfilled environments that use realms, it's currently not possible to listen to global errors and unhandled rejections.

onerror / onunhandledrejection handlers

e.g.

window.onerror = (...args) => {
  console.log('### ERROR', args)
};

globalThis.onerror = (...args) => {
  console.log('### ERROR', args)
};

the following works btw. but is not exhaustive enough because libs like sentry and bugsnag attach themselves to window or globalThis

onerror = (...args) => {
  console.log('### ERROR', args)
};

We now make this work by adding event listeners for those events the polyfill window instance that just forwards it to the onerror / onunhandledrejection functions. (thanks @igor10k for that idea!). Those events have been available for years so I think that's ok.

This also doesn't work at the moment inside extensions:

globalThis.addEventListener("error", (...args) => {
  console.log('### ERROR', args);
});

This doesn't work because in realms the globalThis.addEventListener is not the one the worker is dispatching error events to. So we need to to dispatch those events manually from the worker to the realm global.
However we can't dispatch the native event because the polyfill dispatchEvent implementation tries to override target on the event instance, which throws for native events. So we need to also polyfill ErrorEvent and PromiseRejectionEvent which can be dispatched

[robin-drexler]

/snapit

[shopify-github-actions-access]

🫰✨ Thanks @robin-drexler! Your snapshot has been published to npm.

Test the snapshot by updating your package.json with the newly published version:

"@remote-dom/polyfill": "0.0.0-snapshot-20250819185911"

[robin-drexler]

/snapit

[shopify-github-actions-access]

🫰✨ Thanks @robin-drexler! Your snapshot has been published to npm.

Test the snapshot by updating your package.json with the newly published version:

"@remote-dom/polyfill": "0.0.0-snapshot-20250819190822"

[robin-drexler]

I was unsure if this would lead to infinite calls when we do setGlobal or setGlobalThis, but it worked for me when I tried it.

[robin-drexler]

/snapit

[shopify-github-actions-access]

🫰✨ Thanks @robin-drexler! Your snapshot has been published to npm.

Test the snapshot by updating your package.json with the newly published version:

"@remote-dom/polyfill": "0.0.0-snapshot-20250821140812"

[robin-drexler]

the original on error handler in libdom is typed weirdly in a way where the argument could either be an event object or the 5 args. But in reality it's only the 5 args. https://developer.mozilla.org/en-US/docs/Web/API/Window/error_event#syntax

So we're creating our own type

[robin-drexler]

I think add and remove listener on the polyfill isn't correctly typed. e.g. it doesn't know that unhandledrejection events should have an event object with promise and reason which is causing issues here. type casting as any for now

[lemonmade]

Great job!

[waseembahralaseel-cell]

Fix my problem too