Inconsistent Treatment of undefined in SSR

[dairyisscary]

Describe the bug

Attributes with an undefined runtime value are treated differently in SSR than they are in client rendering. In client rendering, attributes are completely removed when the value is undefined but in SSR, sometimes the attribute is serialized with "" and sometimes its serialized as string "undefined".

In my particular example, I'm using aria-describedby, where a valid ID is required (and in my particular case, isn't known until the client hydrates so SSR without the attribute is desirable).

Your Example Website or App

https://playground.solidjs.com/?hash=-776479397&version=1.3.13

Steps to Reproduce the Bug or Issue

See example, I have static div, <Dynamic /> and a custom component using spread. Custom component and Dynamic seem to behave the same but I've included both just in case.

Expected behavior

I'm not sure what is correct behavior here, tbh. i definitely think string "undefined" is no good but because of how clever the compiler is at "precompiling" the static bits of the string (in this case the aria-describedby= part), I'm not sure "" is wrong. Though for this particular attribute, i think an HTML validator/spec checker will complain about the empty string.

Screenshots or Videos

No response

Platform

• OS: mac, node v16
• Browser: all
• Version: 1.3.15

Additional context

No response