SVG render issues within #if blocks

[Kabakuro]

Describe the bug

Hey there, I'm currently migrating a project to svelte 5 (It's great so far).

One thing I noticed is that if you have SVG elements in an #if and regular HTML in an :else (or another #if), It won't render the SVG elements. It also errors in the example for using getBBox. I'm guessing this is a namespace issue with if/else blocks?

I understand that this works by using #snippet instead but surely this should just work?

Reproduction

https://svelte.dev/playground/dcb13ede27e9438ba6d2a40002ea36b6?version=5.10.1

Logs

No response

System Info

N/A (using the REPL)

Severity

annoyance

[bdpartridge]

It seems like there's been a regression. See this reproduction of the issue on 5.15.0:

https://svelte.dev/playground/hello-world?version=5.15.0#H4sIAAAAAAAAE3VSTY_TMBD9K6OBA0iNY7f53rQI9oCQ4ITEBXMIrttY6zpR4ra7W-W_IzspJcAqyuS9-XozmlzQVAeJBX799hHOytYgGrNVVjWm0mCV1RIXuFNa9lh8v6B9al22c-DiWvu-bUl_kto638-ql__zi8ZYaWyPBZa96FRrN9xwqw5t01n4JBoDu645AEcSOjZVcrzjpgxvFab0ueHmivyQa473qhNaTkvUUjwcqu6Bo8_EBVr5aLGw3VEOixf2-EN2vsg88MImWlq4-GEGWMPrtmva_s3bf6bvT3s4KXn-0DyuOVKgwBJgCUeoOlUFtdpupVmPjeAdmKPWUABHNznHwUtdXqnduPfgKLelJ5tJvgxH6lNDtfNJZVvZGrZrjl8yoPcrEmc5OPkryvoRZeMTTCyYUOBQ9nygwGIRrEiWAA3SYEVYFKRB2o8AUveCI-DICJzvmeOmDN0Qm7_GYYywKIGYrLLsc0LybAk5ieMlRCRb5ZCSiOYiICyPJxOz5YRSmgL1-HfYRYGCC-klifIEvBXXJBf3X1-rIxKzLPBW3HpcZVzzlKZzcXYTJ5Sy2WJl2J_206Ht03QDd_LLeKiz2tq6AJa0j3ejp5ZqX9uZa6e0LkAcu04aKxrddD4w-PZT1_kf_WP4BYC8LjLJAwAA

If you inspect the <title> element of the second SVG icon, you can see that it has the wrong namespaceURI property: "http://www.w3.org/1999/xhtml".

[trueadm]

@bdpartridge Please create a separate issue, rather than commenting on a closed one.

[bdpartridge]

@trueadm Sorry about that. Created #14814.