`sveltekit:prefetch` seems to be invalid HTML

Describe the problem

Hey, I just validated my SvelteKit website with https://validator.w3.org/nu/ and it heavily complained about sveltekit:prefetch not being valid HTML.

Is this a problem? Maybe if some service wanted to rank the quality of some website, they would use an HTML validator and adjust the ranking accordingly?

Describe the proposed solution

To avoid that, maybe the Svelte compiler could automatically turn such things into a valid HTML attribute like data-sveltekit="prefetch" from where the router can pick it up?

In my imagination this should be fairly easy to implement and would result in valid HTML.

Alternatives considered

No response

Importance

nice to have

Additional Information

Thank you very much for building Svelte!

[Rich-Harris]

As mentioned on the PR, I’m opposed to a transform step that changes sveltekit:prefetch to data-sveltekit-prefetch under the hood (https://github.com/sveltejs/kit/pull/6170#issuecomment-1223322743).

Which means that if we were to make this change, it would be a breaking change — we would no longer be able to use sveltekit:prefetch etc and would have to use the arguably inferior ergonomics of data- prefixes.

If we make such a change, it should be for a good reason, not a speculative one like ‘search engines might downrank you’ or ‘a11y tools might complain’. I’m unaware of any such impacts (and I’d expect more people to have found their way to this thread if there were), so my inclination would be to leave things as they are, but I’d be interested to hear from anyone if there’s a compelling reason to switch?

[ghostdevv]

Could sveltekit:prefetch be internally search & replaced with data-sveltekit-prefetch so it’s not breaking and it keeps the good DX?