feat: deprecate svelte:component

[paoloricciuti]

Svelte 5 rewrite

Close #12668

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[changeset-bot]

🦋 Changeset detected

Latest commit: 63968ea

The changes in this PR will be included in the next version bump.

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[Rich-Harris]

The more I think about this, the more I think we should just treat <foo.bar> as a component. That's what e.g. React and Solid do. No element can have a . in the name (except for custom elements, which are easily identified by the -).

The only sticking point that I'm aware of is Svelte Native, which has something called property elements. @halfnelson would this change be a dealbreaker?

[paoloricciuti]

The more I think about this, the more I think we should just treat <foo.bar> as a component. That's what e.g. React and Solid do. No element can have a . in the name (except for custom elements, which are easily identified by the -).

I mean technically you could have a <weird.element> on the page that is a custom element and not a web component...but to be fair i think it could be safely assumed noone is actually doing stuff like this.

The only sticking point that I'm aware of is Svelte Native, which has something called property elements. @halfnelson would this change be a dealbreaker?

How are they dealing with it? If it's a preprocessor thing wouldn't that be invisible to svelte?

[Rich-Harris]

I have no idea, but it doesn't look like it's preprocessing (there is a Svelte Native preprocessor, but it only replaces bind:value with an event handler)

[paoloricciuti]

I have no idea, but it doesn't look like it's preprocessing (there is a Svelte Native preprocessor, but it only replaces bind:value with an event handler)

I dug a bit: at least from what i could understand they are shimming the dom api and they are swapping document.createElement with something that returns their custom elements that are compatible with NativeScript

https://github.com/halfnelson/svelte-native/blob/058c4e6aea3028151710d5e1317935d9b470a468/src/dom/basicdom/DocumentNode.ts#L23-L29

But if i'm not mistaken thet will need to rewrite this part already right?

[Rich-Harris]

Given that we no longer call document.createElement but instead clone nodes from templates, yes I'd expect that to break

[paoloricciuti]

Given that we no longer call document.createElement but instead clone nodes from templates, yes I'd expect that to break

If they plan to "override" clone node treating <comp.onent> as a component would still break them but let's wait to hear from them what they plan to do to support svelte 5

[paoloricciuti]

@Rich-Harris should we split the svelte:component working from the lowercase object.component warning so that we can at least merge that until we have an answer from @halfnelson ?

[Rich-Harris]

Yeah, that's probably the right move

[paoloricciuti]

Yeah, that's probably the right move

Ok gonna do it quickly and gonna open a new one where we can discuss

[paoloricciuti]

@Rich-Harris should be good to go now, gonna open the second pr with the other code

[bdmackie]

FYI after bumping to 219 I'm getting <svelte:component> is deprecated in runes mode warnings on build even though I'm dynamically rendering the components and not using svelte:component.
Repro: https://stackblitz.com/edit/svelte5-kit-iscomp-d8sd

also FYI - the Svelte 5 docs page still references using svelte:component higher up when talking about components being dynamic.

[paoloricciuti]

FYI after bumping to 219 I'm getting <svelte:component> is deprecated in runes mode errors on build even though I'm dynamically rendering the components and not using svelte:component. Repro: https://stackblitz.com/edit/svelte5-kit-iscomp-d8sd

also FYI - the Svelte 5 docs page still references using svelte:component higher up when talking about components being dynamic.

That's because sveltekit is using it...we should probably ignore it there