css/css-scoping/has-slotted-changing-002.html

<!DOCTYPE HTML>
<html>

<head>
  <meta charset="utf-8">
  <title>Changing content targetting :has-slotted through multiple shadow roots</title>
  <link rel="help" href="https://github.com/w3c/csswg-drafts/pull/10586">
  <script src="/resources/testharness.js"></script>
  <script src="/resources/testharnessreport.js"></script>
  <script src="/resources/testdriver.js"></script>
  <script src="/resources/testdriver-vendor.js"></script>
  <script src="/resources/testdriver-actions.js"></script>
</head>

<body>

  <my-element id="test">Test</my-element>
  <template id="myTemplate">
    <slot></slot>
    <p id="target">This text will be styled.</p>
    <style>
    p {
      color: rgb(0 255 0);
    }
    slot:not(:has-slotted) + p {
      color: rgb(0 0 255);
    }
    </style>
  </template>

  <script>
    customElements.define('my-element', class extends HTMLElement {
      constructor() {
        super();
        this.attachShadow({
          mode: 'open',
          slotAssignment: 'manual',
        });
        this.shadowRoot.append(myTemplate.content.cloneNode(true));
      }

      get slot() {
        return this.shadowRoot.querySelector('slot');
      }
    });

    const blue = 'rgb(0, 0, 255)';
    const green = 'rgb(0, 255, 0)';
    test(function (t) {
      const test = document.getElementById('test');
      const target = test.shadowRoot.getElementById('target');
      t.add_cleanup(() => { test.innerHTML = 'Test' });
      let styles = getComputedStyle(target);
      assert_equals(styles.getPropertyValue('color'), blue);
    }, "empty node is blue");

    test(function (t) {
      const test = document.getElementById('test');
      const target = test.shadowRoot.getElementById('target');
      t.add_cleanup(() => { test.innerHTML = 'Test' });
      test.slot.assign(test.childNodes[0])
      styles = getComputedStyle(target);
      assert_equals(test.slot.assignedNodes().length, 1);
      assert_equals(styles.getPropertyValue('color'), green);
      test.slot.assign()
      styles = getComputedStyle(target);
      assert_equals(styles.getPropertyValue('color'), blue);
    }, "manually assigning a text node is green, emptying assignment is blue");

    test(function (t) {
      const test = document.getElementById('test');
      const target = test.shadowRoot.getElementById('target');
      t.add_cleanup(() => { test.innerHTML = 'Test' });

      test.innerHTML = '<div></div>';
      assert_equals(styles.getPropertyValue('color'), blue);

      test.slot.assign(...test.children)
      styles = getComputedStyle(target);
      assert_equals(test.slot.assignedNodes().length, 1);
      assert_equals(styles.getPropertyValue('color'), green);
      test.slot.assign()
      styles = getComputedStyle(target);
      assert_equals(styles.getPropertyValue('color'), blue);
    }, "manually assigning a Element is green, emptying assignment is blue");
  </script>
</body>

</html>