Bug in rule “validation.css”: “--color” is an unknown vendor extension

[svgeesus]

No, all properties which start with a double dash "--" are CSS Custom Properties not "vendor extensions". I mean come on, CSS Custom Properties for Cascading Variables Module Level 1 has been in CR since 2015 and is implemented in all browsers.

Again, a poorly-maintained CSS Validator that is half-a decade behind the CSS specifications is adding negative value here.

Found while checking https://www.w3.org/TR/2020/WD-css-color-4-20201112/.

[xfq]

It seems to be tracked in w3c/css-validator#111

[svgeesus]

Thanks. So the bug was reported in 2017 and is still not fixed 3 years later.

[Eunomiac]

Is there an update on this? I tried using the WC3 CSS Validation Service on my CSS, and was flooded with a plethora of non-errors resulting from the validator's apparent inability to play nice with CSS variables.

First three reported errors:

The relevant lines of CSS referenced in the above excerpt:

• [62]   background-image: radial-gradient(var(--dotBright), var(--dotDark));
• [561] --bgH2: linear-gradient(270deg, var(--accentUp2), var(--accentUp4), var(--accentUp2));
• [642] --maxHeightInput: calc(var(--lineHeightBody) * 1.2);

I've been using CSS variables for years now, and I don't quite understand how a validator can be relevant for anything but the simplest applications of CSS without at least some acknowledgment of the existence of custom CSS variables?

[dontcallmedom]

@Eunomiac the place to discuss the CSS validator itself is https://github.com/w3c/css-validator/ - the particular discussion on CSS variable support is at w3c/css-validator#111

[Eunomiac]

@dontcallmedom Ah! My bad, I shall post over there --- should I delete my post here, or is that frowned upon?

[dontcallmedom]

I don't think it's frowned upon, but I also believe there is no harm in leaving it here :)

For completeness, conversation on w3c/css-validator#111 has been locked since what is needed for this issue at this point is actual contributions rather than further assertion this is a highly wanted feature