css/css-syntax/custom-property-rule-ambiguity.html

<!DOCTYPE html>
<title>CSS Syntax: Rules that look like custom properties</title>
<link rel="help" href="https://drafts.csswg.org/css-syntax/#consume-qualified-rule">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>

<style id=stylesheet1>
  .a { }
  --x:hover { } /* Ambiguous "rule" */
  .b { }
</style>
<script>
  test(() => {
    let rules = stylesheet1.sheet.rules;
    assert_equals(rules.length, 2);
    assert_equals(rules[0].selectorText, '.a');
    assert_equals(rules[1].selectorText, '.b');
  }, 'Rule that looks like a custom property declaration is ignored');
</script>

<!-- https://github.com/w3c/csswg-drafts/issues/9336 -->
<style id=stylesheet2>
  .a { }
  --x:hover { ] } /* Ambiguous "rule" */
  .b { }
</style>
<script>
  test(() => {
    let rules = stylesheet2.sheet.rules;
    assert_equals(rules.length, 2);
    assert_equals(rules[0].selectorText, '.a');
    assert_equals(rules[1].selectorText, '.b');
  }, 'Rule that looks like an invalid custom property declaration is ignored');
</script>

<style id=stylesheet3>
  div {
    .a { }
    --x:hover { }
    .b { }
  }
</style>
<script>
  test(() => {
    let rules = stylesheet3.sheet.rules;
    assert_equals(rules.length, 1);
    assert_equals(rules[0].selectorText, 'div');
    let div = rules[0];
    let childRules = div.cssRules;
    assert_equals(childRules.length, 2);
    assert_equals(childRules[0].selectorText, '& .a');
    assert_true(childRules[1] instanceof CSSNestedDeclarations)
    let x = childRules[1].style.getPropertyValue('--x');
    assert_equals(x.trim(), 'hover { }\n    .b { }');
  }, 'Nested rule that looks like a custom property declaration');
</script>

<!-- https://github.com/w3c/csswg-drafts/issues/9336 -->

<style id=stylesheet4>
  div {
    .a { }
    --x:hover { ] }
    .b { }
  }
</style>
<script>
  test(() => {
    let rules = stylesheet4.sheet.rules;
    assert_equals(rules.length, 1);
    assert_equals(rules[0].selectorText, 'div');
    let div = rules[0];
    // There is no valid --x declaration, because mismatched ] is not allowed
    // in custom properties.
    let x = div.style.getPropertyValue('--x');
    assert_equals(x, '');
    // We should also not have restarted parsing as a nested style rule,
    // and instead we should have "consumed the remnants of a bad declaration",
    // which skips to the next semicolon (or end-of-block).
    // So in other words, there should be no nested '.b.' child rule here.
    let childRules = div.cssRules;
    assert_equals(childRules.length, 1);
    assert_equals(childRules[0].selectorText, '& .a');
  }, 'Nested rule that looks like an invalid custom property declaration');
</script>