Attribute value "until-found" for hidden attribute is incorrectly normalized #5073
Description
Description
The hidden="until-found" attribute value (introduced in HTML Living Standard) is not correctly preserved when loading HTML via cheerio.load(). Instead, it is being normalized to hidden or an undefined, treating it as a legacy boolean attribute.
https://developer.mozilla.org/en-US/docs/Web/HTML/Reference/Global_attributes/hidden#description
const html = `
<!DOCTYPE html>
<!-- Sample: popover -->
<dialog id="popover-auto" popover="auto"></dialog>
<dialog id="popover-true" popover></dialog>
<dialog id="popover-false"></dialog>
<dialog id="popover-string-empty" popover></dialog>
<!-- hidden -->
<div id="hidden-until-found" hidden="until-found"></div>
<div id="hidden-true" hidden></div>
<div id="hidden-false"></div>
<div id="hidden-string-empty" hidden></div>
`;~/projects/stackblitz-starters-bnzemr2z
❯ node index.js
{ id: 'popover-auto', expected: 'auto', actual: 'auto' }
{ id: 'popover-true', expected: '', actual: '' }
{ id: 'popover-false', expected: undefined, actual: undefined }
{ id: 'popover-string-empty', expected: '', actual: '' }
{ id: 'hidden-until-found', expected: 'until-found', actual: 'hidden' }
{ id: 'hidden-true', expected: '', actual: 'hidden' }
{ id: 'hidden-false', expected: undefined, actual: undefined }
{ id: 'hidden-string-empty', expected: '', actual: 'hidden' }https://stackblitz.com/edit/stackblitz-starters-bnzemr2z
Environment
cheerio version: 1.2.0
node version: v24.1.0