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Test Info: Warnings

<!DOCTYPE html>
<link rel="help" href="https://github.com/whatwg/html/pull/9144">
<link rel="author" href="mailto:xiaochengh@chromium.org">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<style>
body {
margin: 0;
}
.anchor {
width: 100px;
height: 100px;
margin-left: 50px;
margin-top: 50px;
background: orange;
}
.target {
position: absolute;
left: anchor(right, 123px);
top: anchor(top, 456px);
width: 100px;
height: 100px;
background: lime;
}
</style>
<div class="anchor" id="anchor1"></div>
<div class="anchor" id="anchor2"></div>
<div class="target" id="target1" anchor="anchor1"></div>
<div class="target" id="target2" anchor="anchor1"></div>
<script>
test(() => {
document.body.offsetLeft; // Force layout
target1.setAttribute('anchor', 'anchor2');
assert_equals(target1.offsetLeft, 150);
assert_equals(target1.offsetTop, 200);
target1.setAttribute('anchor', 'anchor1');
assert_equals(target1.offsetLeft, 150);
assert_equals(target1.offsetTop, 50);
}, 'Layout should be updated when anchor attribute changes to another element');
test(() => {
document.body.offsetLeft; // Force layout
target2.setAttribute('anchor', 'nonexist-anchor');
assert_equals(target2.offsetLeft, 123);
assert_equals(target2.offsetTop, 456);
}, 'Layout should be updated when anchor attribute changes to a non-existent element');
</script>