Bug 292968 – REGRESSION (Safari 18.4): Declarative shadow DOM and custom elements do not work with parseUnsafeHTML

• Status: RESOLVED
• Resolution: FIXED
• Component: DOM

Hello,

On Safari exclusively (it works on Chrome), parseUnsafeHTML and setUnsafeHTML are not working with nested web components. Even though the web components are inserted into the page, the `connectedCallback` is never called. You can experience the issue here: https://codepen.io/bakura10/pen/LEEqGmy

On Chrome, both messages are logged. On Safari, the nested web components is not initialized at all.

Thanks.

After further testing, it appears to work on Safari 18.1, but not on 18.3 and 18.4. It therefore seems to be a recent regression.

[Ahmad Saleem]

***

[Radar WebKit Bug Importer]

<rdar://problem/151273154>

[Ahmad Saleem]

*** Safari Technology Preview 218 ***

"Bar: Should be called"

*** Chrome Canary 138.0.7177.0 (Official Build) canary (arm64) ***
"Bar: Should be called"
"Bim: Should be called"

*** Firefox Nightly 140 (20250513214736) ***

"Bar: Should be called"
"Bim: Should be called"

[Alexey Proskuryakov]

Thank you for the report! Between 18.2 and 18.3, guessing the former because it was a release with more changes overall.

[Alexey Proskuryakov]

Actually, looks like our testing so far disagrees, and 18.3 worked.

[Ryosuke Niwa]

Created attachment 475277 [details]
Reduction

[Ryosuke Niwa]

Pull request: https://github.com/WebKit/WebKit/pull/45526

[EWS]

Committed 295050@main (6d35fd51666a): <https://commits.webkit.org/295050@main>

Reviewed commits have been landed. Closing PR #45526 and removing active labels.