sousa-gecko/testing/web-platform/tests/custom-elements/Document-createElementNS-prefix-timing.html

<!DOCTYPE html>
<title>Custom Elements: namespace prefix is set after construction per spec</title>
<link rel="help" content="https://dom.spec.whatwg.org/#concept-create-element">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<body>
<script>
// Step 5.1.3.9 of https://dom.spec.whatwg.org/#concept-create-element sets
// the namespace prefix AFTER the constructor returns. These tests verify that
// the prefix is not observable during construction but is correct afterwards.

test(() => {
  let prefixDuringConstructor;
  let tagNameDuringConstructor;

  class PrefixEl extends HTMLElement {
    constructor() {
      super();
      prefixDuringConstructor = this.prefix;
      tagNameDuringConstructor = this.tagName;
    }
  }
  customElements.define('prefix-timing-el', PrefixEl);

  const el = document.createElementNS('http://www.w3.org/1999/xhtml', 'p:prefix-timing-el');

  assert_equals(prefixDuringConstructor, null,
    'prefix should be null during constructor (set after construction per step 5.1.3.9)');
  assert_equals(tagNameDuringConstructor, 'PREFIX-TIMING-EL',
    'tagName during constructor should not include prefix');

  assert_equals(el.prefix, 'p',
    'prefix should be set after construction');
  assert_equals(el.tagName, 'P:PREFIX-TIMING-EL',
    'tagName after construction should include prefix');
}, 'Autonomous custom element prefix is set after constructor returns');

test(() => {
  let innerPrefix;
  let outerPrefixDuringConstructor;

  class ReentrantEl extends HTMLElement {
    static callCount = 0;
    constructor() {
      super();
      if (ReentrantEl.callCount++ === 0) {
        // Create another instance via direct construction re-entrantly
        // during outer (createElementNS-initiated) construction.
        const inner = new ReentrantEl();
        innerPrefix = inner.prefix;
      }
      outerPrefixDuringConstructor = this.prefix;
    }
  }
  customElements.define('reentrant-prefix-el', ReentrantEl);

  const el = document.createElementNS('http://www.w3.org/1999/xhtml', 'r:reentrant-prefix-el');

  assert_equals(outerPrefixDuringConstructor, null,
    'outer prefix should be null during constructor');
  assert_equals(innerPrefix, null,
    'directly-constructed inner element should not inherit outer prefix');
  assert_equals(el.prefix, 'r',
    'outer element prefix should be set after construction');
}, 'Reentrant construction does not leak prefix between instances');

test(() => {
  let prefixDuringConstructor;
  let outerElement;

  class ReentrantNSEl extends HTMLElement {
    static callCount = 0;
    constructor() {
      super();
      if (ReentrantNSEl.callCount++ === 0) {
        outerElement = this;
        // Create another instance via createElementNS re-entrantly.
        const inner = document.createElementNS('http://www.w3.org/1999/xhtml', 'q:reentrant-ns-el');
        assert_equals(inner.prefix, 'q', 'inner element created during outer constructor should have its own prefix');
      }
      prefixDuringConstructor = this.prefix;
    }
  }
  customElements.define('reentrant-ns-el', ReentrantNSEl);

  const el = document.createElementNS('http://www.w3.org/1999/xhtml', 'p:reentrant-ns-el');

  assert_equals(el.prefix, 'p',
    'outer element should have its own prefix');
  assert_equals(outerElement, el,
    'outerElement reference should match returned element');
}, 'Nested createElementNS calls do not corrupt prefix state');
</script>
</body>