[Webkit-unassigned] [Bug 198204] New: :matches() shouldn't allow pseudo-elements inside.

Thu May 23 18:27:35 PDT 2019

https://bugs.webkit.org/show_bug.cgi?id=198204

            Bug ID: 198204
           Summary: :matches() shouldn't allow pseudo-elements inside.
           Product: WebKit
           Version: WebKit Nightly Build
          Hardware: Unspecified
                OS: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: CSS
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: emilio at crisal.io
                CC: koivisto at iki.fi, rniwa at webkit.org

Bug 198147 introduced a check for sub-selectors to know the property whitelist to apply.

I think the right fix is not to parse :matches(::before) to begin with. It just doesn't really make much sense that webkit parses stuff like `:matches(::before):matches(::before)::before`. 

Other pseudo-classes like :host() or pseudo-elements like :host-context() don't allow pseudo-elements in the grammar for this very same reason.

Also, in case you disagree, the check introduced in that bug wouldn't produce the correct behavior, I bet (haven't built myself) that that patch would stop the background / width / etc. from applying to the <li> element in the following test-case:

<!doctype html>
<style>
  :matches(::marker, li) {
    width: 100px;
    height: 100px;
    background: green;
  }
</style>
<li>foo</li>

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