lang-attribute-document-element-replacement.html

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This WPT test may be referenced by the following Test IDs:
- /html/dom/elements/global-attributes/lang-attribute-document-element-replacement.html - WPT Dashboard Interop Dashboard

<!DOCTYPE html>

<html>

<head>

<meta charset="utf-8">

<title>lang attribute: disconnected subtree after document element replacement</title>

<link rel="help" href="https://html.spec.whatwg.org/#the-lang-and-xml:lang-attributes">

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

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

</head>

<body>

<script>

test(() => {

    const iframe = document.createElement("iframe");

    document.body.append(iframe);

    const doc = iframe.contentDocument;

    doc.documentElement.lang = "de";

    const container = document.createElement("div");

    const child = document.createElement("div");

    container.append(child);

    doc.body.append(container);

    assert_true(container.matches(":lang(de)"), "container should match de while connected");

    assert_true(child.matches(":lang(de)"), "child should match de while connected");

    const oldRoot = doc.documentElement;

    oldRoot.remove();

    const newRoot = document.createElement("html");

    newRoot.lang = "zh";

    doc.append(newRoot);

    assert_true(container.matches(":lang(de)"), "container should still match de after document element replacement");

    assert_false(container.matches(":lang(zh)"), "container should not match zh after document element replacement");

    assert_true(child.matches(":lang(de)"), "child should still match de after document element replacement");

    assert_false(child.matches(":lang(zh)"), "child should not match zh after document element replacement");

    iframe.remove();

}, "Disconnected descendants of a replaced document element should resolve lang from their actual ancestor");

</script>

</body>

</html>