imperative-slot-fallback-clear.html

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This WPT test may be referenced by the following Test IDs:
- /shadow-dom/imperative-slot-fallback-clear.html - WPT Dashboard Interop Dashboard

<!DOCTYPE html>

<title>Imperative Slot API: fallback should be cleared after slot assignment</title>

<link rel="author" href="mailto:xiaochengh@chromium.org">

<link rel="help" href="https://bugs.chromium.org/p/chromium/issues/detail?id=1292292">

<script src="/resources/testharness.js"></script>

<script src="/resources/testharnessreport.js"></script>

<div>

  <div id="host1"><span></span></div>

  <div id="host2"><span></span></div>

</div>

<script>

test(() => {

  const host = document.getElementById('host1');

  const shadow = host.attachShadow({mode: 'open', slotAssignment: 'manual'});

  shadow.innerHTML = '<slot>fallback</slot>';

  host.offsetHeight; // Force layout

  const slot = shadow.firstChild;

  slot.assign(host.firstChild);

  assert_array_equals(slot.assignedNodes(), [host.firstChild]);

  assert_equals(host.offsetHeight, 0, 'Fallback content should not be rendered');

}, 'Text node fallback should be cleared in a subsequently layout');

test(() => {

  const host = document.getElementById('host2');

  const shadow = host.attachShadow({mode: 'open', slotAssignment: 'manual'});

  shadow.innerHTML = '<slot><span>fallback</span></slot>';

  host.offsetHeight; // Force layout

  const slot = shadow.firstChild;

  slot.assign(host.firstChild);

  assert_array_equals(slot.assignedNodes(), [host.firstChild]);

  assert_equals(host.offsetHeight, 0, 'Fallback content should not be rendered');

}, 'Element fallback should be cleared in a subsequent layout');

</script>