Bug 283222 – Poor performance of querySelectorAll() with descendant selectors (:has())

• Component: CSS
• Status: RESOLVED FIXED

[Jeff Johnson]

I discovered this bug while investigating another bug, Poor performance of selector div:has(img) button https://bugs.webkit.org/show_bug.cgi?id=283220

Steps to reproduce:
1. Open https://sdpc.a4l.org/search_national.php
2. Open the web inspector
3. document.querySelectorAll('foobar div:has(img) button')

Expected results: The node list is returned immediately.

Actual results: The node list takes about 3 seconds to return.

Since document.querySelectorAll('foobar') contains no items, the rest of the selector should be irrelevant and ignored. But WebKit is still clearly calculating the 'div:has(img) button' part of the selector.

[Radar WebKit Bug Importer]

<rdar://problem/140093151>

[Karl Dubost]

var startTime = performance.now(); document.querySelectorAll('foobar div:has(img) button'); var endTime = performance.now(); console.log(`${endTime - startTime} milliseconds`)

Safari:  2247 ms
Firefox:    2 ms
Chrome:    22 ms


Safari Technology Preview  207           20621.1.4.3
Firefox Nightly            134.0a1       13424.11.7
Google Chrome Canary       133.0.6843.0  6843.0

[Antti Koivisto]

Pull request: https://github.com/WebKit/WebKit/pull/36893

[EWS]

Committed 286908@main (cdba6f7e0a32): <https://commits.webkit.org/286908@main>

Reviewed commits have been landed. Closing PR #36893 and removing active labels.

[Antti Koivisto]

*** Bug 283220 has been marked as a duplicate of this bug. ***