Lighthouse says: Does not use passive listeners to improve scrolling performance

[AndrewSavetchuk]

Hi. Can you tell me where event listeners are registered in raven.js, please?

Google Lighthouse report says raven.js should use passive event listeners:

More info here: https://developers.google.com/web/tools/lighthouse/audits/passive-event-listeners

[kamilogorek]

Hey, we don't have any listeners ourselves. Line 1262 points to a breadcrumb wrapper which captures unhandled errors in addEventListener calls.
It's a pass-through function though, so the way you call your addEventListener methods, will be exactly what ends up being called.

[devForTheFuture]

How do I remove the issue?

Does not use passive listeners to improve scrolling performance
Consider marking your touch and wheel event listeners as passive to improve your page's scroll performance.

URL	Location
/5.6.3/bundle.min.js(browser.sentry-cdn.com)	line: 1

[aaalekseev]

Guys, does anyone solved this issue?

[rhcarvalho]

There doesn't seem to be anything to be done on the SDK side here.

Closing to clean up the issue tracker, please feel free to comment if I have misinterpreted the status.

[VivienGiraud]

The "issue" is still there.

[rhcarvalho]

@VivienGiraud please see #2227 (comment).

[...] we don't have any listeners ourselves. [...] a breadcrumb wrapper [...] captures unhandled errors in addEventListener calls.
It's a pass-through function though, so the way you call your addEventListener methods, will be exactly what ends up being called.

---

This is part of the Lighthouse report for a page using version 5.21.4 of the SDK (the sentry.io application itself).
You can reproduce by running Lighthouse on your organization issue stream.

For all I can tell, this issue is simply an unfortunate case of the SDK being flagged by Lighthouse because it wraps user code to catch errors.

[rhcarvalho]

@VivienGiraud out of curiosity, I've used a filter to block/remove the Sentry SDK from dev.tridea.io, and then re-run Lighthouse:

Instead of Sentry, now Lighthouse blames https://dev.tridea.io/static/js/vendors/siema-1.5.1-min.js for the non-passive listeners.

Mystery revealed, these are probably the event listeners that affect your page scrolling performance:

https://github.com/pawelgrzybek/siema/blob/7f762aa496269b7dfb6685f633cda980df96fa06/src/siema.js#L104-L107

[VivienGiraud]

Love it!
Thanks for the remote debugging :)
I think Sentry just wrap everything so the root cause isn't raise clearly.
Thanks @rhcarvalho