css/css-properties-values-api/at-property-stylesheets.html

<!DOCTYPE html>
<title>Verify that the correct registration is selected for mutated stylesheets</title>
<link rel="help" href="https://drafts.css-houdini.org/css-properties-values-api-1/#determining-registration">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="./resources/utils.js"></script>
<div id=div></div>
<script>

test(() => {
  with_at_property({
    syntax: '"<length>"',
    inherits: false,
    initialValue: '1px'
  }, (name) => {
    assert_equals(getComputedStyle(div).getPropertyValue(name), '1px');
  });
}, '@property detected when stylesheet appears');

test(() => {
  let name = generate_name();
  with_at_property({
    name: name,
    syntax: '"<length>"',
    inherits: false,
    initialValue: '1px'
  }, (name) => {
    assert_equals(getComputedStyle(div).getPropertyValue(name), '1px');
  });
  assert_equals(getComputedStyle(div).getPropertyValue(name), '');
}, '@property removal detected when last @property rule disappears');

test(() => {
  with_at_property({
    syntax: '"<length>"',
    inherits: false,
    initialValue: '1px'
  }, (name1) => {
    with_at_property({
      syntax: '"<length>"',
      inherits: false,
      initialValue: '2px'
    }, (name2) => {
      assert_equals(getComputedStyle(div).getPropertyValue(name2), '2px');
    });
  });
}, '@property detected in second stylesheet');

test(() => {
  let name2 = generate_name();
  with_at_property({
    syntax: '"<length>"',
    inherits: false,
    initialValue: '1px'
  }, (name1) => {
    with_at_property({
      name2: name2,
      syntax: '"<length>"',
      inherits: false,
      initialValue: '2px'
    }, (name2) => {
      assert_equals(getComputedStyle(div).getPropertyValue(name2), '2px');
    });
    assert_equals(getComputedStyle(div).getPropertyValue(name2), '');
  });
}, '@property removal detected with removal of second stylesheet');

test(() => {
  let name1 = generate_name();
  let name2 = generate_name();

  let sheet1 = `
    @property ${name1} {
      inherits: false;
      syntax: "<length>";
      initial-value: 1px;
    }
  `;
  let sheet2 = `
    @property ${name2} {
      inherits: false;
      syntax: "<length>";
      initial-value: 2px;
    }
  `;

  let node1 = document.createElement('style');
  let node2 = document.createElement('style');

  node1.textContent = sheet1;
  node2.textContent = sheet2;

  try {
    document.body.append(node1, node2);
    assert_equals(getComputedStyle(div).getPropertyValue(name1), '1px');
    assert_equals(getComputedStyle(div).getPropertyValue(name2), '2px');
    node1.remove();
    assert_equals(getComputedStyle(div).getPropertyValue(name1), '');
    assert_equals(getComputedStyle(div).getPropertyValue(name2), '2px');
  } finally {
    node1.remove();
    node2.remove();
  }
}, '@property removal detected with removal of first stylesheet');

</script>