Bug 241433

Summary:	Make CSS custom properties that are invalid at computed value time guaranteed-invalid
Product:	WebKit	Reporter:	Shaw Jia <xiaozj>
Component:	CSS	Assignee:	Nobody <webkit-unassigned>
Status:	RESOLVED CONFIGURATION CHANGED
Severity:	Normal	CC:	augus.dupin, bramus, james0x57, justin_michaud, koivisto, ntim, philip, simon.fraser, webkit-bug-importer
Priority:	P2	Keywords:	BrowserCompat, InRadar
Version:	Safari 15
Hardware:	All
OS:	All

Description Shaw Jia 2022-06-08 13:30:19 PDT

Same as this Firefox bug: https://phabricator.services.mozilla.com/D116460

Also codepen demo: https://codepen.io/Miragecraft/pen/XWaLxNb

In short, when assigning an invalid CSS custom property to another custom property, it makes the final value unset (which means "inherit" for custom properties) instead of initial.

Comment 1 Bruno Stasse 2022-06-09 05:35:08 PDT

WebKit's behaviour now differs from both Gecko's and Blink's, causing an interoperability issue.

Comment 2 Radar WebKit Bug Importer 2022-06-15 13:31:13 PDT

<rdar://problem/95234259>

Comment 3 Philip Jägenstedt 2022-11-10 03:08:51 PST

Here's the relevant spec change:
https://github.com/w3c/csswg-drafts/issues/5370
https://github.com/w3c/csswg-drafts/pull/6006

And Safari-only failures in WPT:
https://wpt.fyi/results/css/css-variables/variables-substitute-guaranteed-invalid.html?run_id=6317090990981120&run_id=5097315145089024&run_id=5104235344035840&run_id=5084375415259136

The reason I noticed is because this issue was specifically called out in a freeform text comment from State of CSS 2022.

Comment 4 Antti Koivisto 2023-02-15 09:02:11 PST

Is now working.

Comment 5 Antti Koivisto 2023-02-15 09:05:05 PST

That is css/css-variables/variables-substitute-guaranteed-invalid.html WPT is passing.