Issue with MathML support

[lukewarlow]

Vue version

3.5.0-alpha1

Link to minimal reproduction

https://play.vuejs.org/#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

Steps to reproduce

Load the Vuejs playground link, on page load it will show the msup element correctly has the MathML namespace. If you click the button which will swap the child element to a mrow element you'll see it now incorrectly has an XHTML namespace (the default for html), clicking the button again to swap back to the msup results in it being in the XHTML namespace.

What is expected?

The elements should keep their MathML namespace even during Vue's conditional rendering (and other dynamic features), like SVG does.

What is actually happening?

Once the element is updated dynamically it loses its parent context and reverts back to the XHTML namespace.

System Info

No response

Any additional comments?

No response