Add :is(), retain argument selectors for :not()/:has()/:matches(), fix forgiving-list specificity - #201
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TylerBrinks merged 1 commit intoJul 23, 2026
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…x forgiving-list specificity :not(), :has() and :matches() collapsed their parsed argument to a formatted string and wrapped it in an opaque PseudoClassSelector, so the inner selector object - and any way to inspect or re-match it - was lost. Introduce NotSelector, HasSelector and MatchesSelector, each retaining the parsed argument ISelector, and add :is() as the modern alias of :matches() (they share MatchesSelector; a Keyword field controls which form it serializes to). Fix specificity to match CSS Selectors 4 16.1: the specificity of an :is()/:not()/:has() is that of the most specific complex selector in its argument. That requires a selector list to report the static max of its alternatives rather than their sum, so Selectors.Specificity becomes virtual and ListSelector overrides it. CompoundSelector keeps the sum, which is correct - its members all constrain one element. Verified against the spec's own examples: :is(em, #foo) is (1,0,0) and :not(em, strong#foo) is (1,0,1).
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Problem
:not(),:has()and:matches()throw away their parsed argument. Each function state formats the inner selector back to a string and wraps it in an opaquePseudoClassSelector:So after parsing
a:not(.foo)there is no way to reach the.fooselector object — only its round-tripped text survives. And:is(), the current name for:matches()(CSS Selectors 4 §4.2), isn't recognized at all.Changes
NotSelector/HasSelector/MatchesSelector— each retains the parsed argumentISelector(exposed asInner) and round-trips correctly.:is()as the modern alias of:matches(). Both shareMatchesSelector; aKeywordfield controls whether it serializes as:is(...)or:matches(...).Forgiving-list specificity per CSS Selectors 4 §16.1:
A selector list must therefore report the max of its alternatives, not their sum.
Selectors.SpecificitybecomesvirtualandListSelectoroverrides it to the max.CompoundSelectorkeeps the sum — correct, since its members all constrain one element.Verified against the spec's own examples
:is(em, #foo)(1,0,0):not(em, strong#foo)(1,0,1)Tests
11 tests in
SelectorObjectModelTests.cs: each function produces its typed selector and retainsInner;:is()/:matches()round-trip to their own keyword; the two spec examples plusa:not(.foo)/a:has(.foo)/a:is(.foo, #bar)specificities; and that a list's specificity is the max while a compound's stays the sum.The full suite (1263 existing tests) stays green — the specificity change regresses nothing — and all seven target frameworks build with no new warnings. The new selector types are additive; the only behavioural change to an existing type is
ListSelector.Specificity(sum → max), which is the spec fix above.