Support for the :where pseudoclass function

Hi there! Crossposting an issue from https://github.com/stylelint/stylelint/issues/5065 submitted by @jonathantneal.

It seems as if specificity doesn’t properly support the rules around the :where() pseudoclass function. In particular, the spec ref says:

Unlike :is(), neither the :where() pseudo-class, nor any of its arguments, contribute to the specificity of the selector—its specificity is always zero.

In contrast, trying this out in the Specificity Calculator or using the library, cases like :where(hr) have a nonzero specificity.

(in turn, this has triggered an issue in stylelint’s no-descending-specificity rule)

I’m not familiar with this package, but more than happy to take a look at what needs to be done!

MDN ref & spec ref for :where().

[bartveneman]

Looks like @bramus did the work and implemented the CSSTree approach in a new library: https://github.com/bramus/js-specificity

[timbomckay]

Any progress on this? I’ve been reviewing normalize/reset stylesheets and a significant amount of them are utilizing :where(). It’s rather confusing coming to the css specificity calculator to see it not working. If it’s not supported there should at least be an alert stating it’s not supported.