<!DOCTYPE html>
<link rel="help" href="https://drafts.css-houdini.org/css-properties-values-api-1/#conditional-rules">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script>
CSS.registerProperty({
name: '--length',
syntax: '<length>',
initialValue: '0px',
inherits: false
});
</script>
<style>
#target { color: red; }
@supports(--length: green) {
#target { color: rgb(1, 2, 3); }
}
</style>
<div id=target></div>
<script>
test(function() {
let cs = getComputedStyle(target);
assert_equals(cs.getPropertyValue('color'), 'rgb(1, 2, 3)');
}, '@supports should ignore registered syntax');
test(function() {
assert_true(CSS.supports('--length: red'));
assert_true(CSS.supports('--length: 10px'));
assert_true(CSS.supports('--length: anything, really'));
}, 'CSS.supports(conditionText) should ignore registered syntax');
test(function() {
assert_true(CSS.supports('--length', 'red'));
assert_true(CSS.supports('--length', '10px'));
assert_true(CSS.supports('--length', ' anything, really'));
}, 'CSS.supports(property, value) should ignore registered syntax');
</script>