custom-elements/element-internals-shadowroot.html

<!DOCTYPE html>
<meta charset="utf-8">
<title>ElementInternals.shadowRoot</title>
<link rel="author" href="mailto:masonf@chromium.org">
<link rel="help" href="https://html.spec.whatwg.org/#dom-elementinternals-shadowroot">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>

<script>

test(() => {
  let constructed = false;
  customElements.define('custom-open', class extends HTMLElement {
    constructor() {
      super();
      const elementInternals = this.attachInternals();
      assert_equals(elementInternals.shadowRoot, null);
      const shadow = this.attachShadow({mode: 'open'});
      assert_equals(elementInternals.shadowRoot, shadow);
      constructed = true;
    }
  });
  const element = document.createElement('custom-open');
  assert_true(constructed);
}, 'ElementInternals.shadowRoot allows access to open shadow root');

test(() => {
  let constructed = false;
  customElements.define('custom-closed', class extends HTMLElement {
    constructor() {
      super();
      const elementInternals = this.attachInternals();
      assert_equals(elementInternals.shadowRoot, null);
      const shadow = this.attachShadow({mode: 'closed'});
      assert_equals(elementInternals.shadowRoot, shadow);
      assert_equals(this.shadowRoot, null);
      constructed = true;
    }
  });
  const element = document.createElement('custom-closed');
  assert_true(constructed);
}, 'ElementInternals.shadowRoot allows access to closed shadow root');

test(() => {
  let constructed = false;
  const element = document.createElement('x-1');
  assert_throws_dom('NotSupportedError', () => element.attachInternals(),'attachInternals cannot be called before definition exists');
  customElements.define('x-1', class extends HTMLElement {
    constructor() {
      super();
      assert_true(!!this.attachInternals());
      constructed = true;
    }
  });
  assert_false(constructed);
  assert_throws_dom('NotSupportedError', () => element.attachInternals(),'attachInternals cannot be called before constructor');
  customElements.upgrade(element);
  assert_true(constructed);
  assert_throws_dom('NotSupportedError', () => element.attachInternals(),'attachInternals already called');
}, 'ElementInternals cannot be called before constructor, upgrade case');

test(() => {
  let constructed = false;
  const element = document.createElement('x-2');
  customElements.define('x-2', class extends HTMLElement {
    constructor() {
      super();
      // Don't attachInternals() here
      constructed = true;
    }
  });
  assert_throws_dom('NotSupportedError', () => element.attachInternals(),'attachInternals cannot be called before constructor');
  assert_false(constructed);
  customElements.upgrade(element);
  assert_true(constructed);
  assert_true(!!element.attachInternals(),'After the constructor, ok to call from outside');
}, 'ElementInternals *can* be called after constructor, upgrade case');

test(() => {
  let constructed = false;
  customElements.define('x-3', class extends HTMLElement {
    constructor() {
      super();
      assert_true(!!this.attachInternals());
      constructed = true;
    }
  });
  const element = document.createElement('x-3');
  assert_true(constructed);
  assert_throws_dom('NotSupportedError', () => element.attachInternals(), 'attachInternals already called');
}, 'ElementInternals cannot be called after constructor calls it, create case');

test(() => {
  let constructed = false;
  const element = document.createElement('x-5');
  customElements.define('x-5', class extends HTMLElement {
    static disabledFeatures = [ 'internals' ];
    constructor() {
      super();
      assert_throws_dom('NotSupportedError', () => this.attachInternals(), 'attachInternals forbidden by disabledFeatures, constructor');
      constructed = true;
    }
  });
  assert_false(constructed);
  assert_throws_dom('NotSupportedError', () => element.attachInternals(), 'attachInternals forbidden by disabledFeatures, pre-upgrade');
  customElements.upgrade(element);
  assert_true(constructed);
  assert_throws_dom('NotSupportedError', () => element.attachInternals(), 'attachInternals forbidden by disabledFeatures, post-upgrade');
}, 'ElementInternals disabled by disabledFeatures');

test(() => {
  let constructed = false;
  const element = document.createElement('x-6');
  const sr = element.attachShadow({mode: 'closed'});
  assert_true(sr instanceof ShadowRoot);
  customElements.define('x-6', class extends HTMLElement {
    constructor() {
      super();
      assert_throws_dom('NotSupportedError', () => this.attachShadow({mode:'open'}), 'attachShadow already called');
      const elementInternals = this.attachInternals();
      assert_equals(elementInternals.shadowRoot, null, 'ElementInternals.shadowRoot should not be available for pre-attached shadow');
      constructed = true;
    }
  });
  assert_false(constructed);
  customElements.upgrade(element);
  assert_true(constructed,'Failed to construct - test failed');
  assert_equals(element.shadowRoot, null, 'shadow root is closed');
}, 'ElementInternals.shadowRoot doesn\'t reveal pre-attached closed shadowRoot');
</script>