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<!DOCTYPE html>
<title>Declarative Shadow DOM after attachShadow</title>
<link rel='author' href='mailto:masonf@chromium.org'>
<link rel='help' href='https://github.com/whatwg/dom/issues/831'>
<script src='/resources/testharness.js'></script>
<script src='/resources/testharnessreport.js'></script>
<body>
<script>
let gotHost = false;
function myObserver(mutationsList, observer) {
for (let mutation of mutationsList) {
for (let n of mutation.addedNodes) {
if (n.id === 'host') {
gotHost = true;
const shadowRoot = n.attachShadow( {mode: 'closed'});
assert_true(!!shadowRoot, 'Unable to attach shadow imperatively');
}
}
}
}
const observer = new MutationObserver(myObserver);
observer.observe(document.body, { childList: true, subtree: true });
assert_false(gotHost, 'No mutations yet');
</script>
<div id=host>
<!-- Ensure observer runs at this point (https://github.com/web-platform-tests/wpt/issues/35393) -->
<script> // some content, which shouldn't be necessary </script>
<template shadowrootmode=open>
Content
<slot>Fallback</slot>
</template>
</div>
<script>
test(t => {
t.add_cleanup(function() { observer.disconnect(); });
assert_true(gotHost);
let host = document.querySelector('#host');
let template = host.querySelector('template');
assert_true(!!template, 'Declarative shadow attach should fail, so template should be left over');
assert_true(!host.shadowRoot, 'Shadow root should be closed (from attachShadow call)');
}, 'Declarative Shadow DOM: declarative shadow should fail if attachShadow() already called');
</script>
</body>
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