chore: small tweaks on set_attributes()

[adiguba]

• See Some remarks about set_attributes() #15399

Changes :

• The parameter skip_warning of set_attributes() was unused : now it's passed to set_attribute().
• The value of the parameter preserve_attribute_case for <svelte:element> is now consistent with regular tags : it's true for custom elements, SVG or MathML (note : is this correct?)
• For <svelte:element>, the value of preserve_attribute_case and is_custom_element are now evaluated when the node is created inside $.element(), and no longer at each update of the template.

Example of generated code :

-	$.element(node, tag, false, ($$element, $$anchor) => {
+	$.element(node, tag, false, ($$element, $$anchor, $$preserve_attribute_case, $$is_custom_element) => {
		let attributes;

		$.template_effect(() => attributes = $.set_attributes($$element, attributes,
				{ title: title(), ...rest }, undefined,
-				$$element.namespaceURI === $.NAMESPACE_SVG,
-				$$element.nodeName.includes('-')
+				$$preserve_attribute_case,
+				$$is_custom_element
		));
	});

Note : I don't known how to test that...

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Tests and linting

• Run the tests with pnpm test and lint the project with pnpm lint

[changeset-bot]

🦋 Changeset detected

Latest commit: 346de0e

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

This PR includes changesets to release 1 package

Name	Type
svelte	Patch

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[svelte-docs-bot]

Preview: https://svelte-dev-git-preview-svelte-15413-svelte.vercel.app/

[github-actions]

Playground

pnpm add https://pkg.pr.new/svelte@15413

[dummdidumm]

what's this change about? Why null in one case and false in the other?

[adiguba]

It's just to generate a null instead of undefined for custom-element :

$.set_attributes(cust_elem, attributes_1, { ...rest }, undefined, true, true);
// =>
$.set_attributes(cust_elem, attributes_1, { ...rest }, null, true, true);

But maybe it's useless...

[Rich-Harris]

I think it's fine to keep it as undefined — there's probably a bunch of places where we have these arguments that are omitted in favour of defaults if there are no subsequent non-falsy arguments, and if we always added this logic it would make the codebase more cluttered. With gzip the extra characters won't matter

[adiguba]

Just a question : what the good value for preserve_attribute_case ?

Like I said currently it's true for custom-element, SVG or MathML on RegularElement, but only on SVG for svelte:element.

I use the value on RegularElement in this PR, but I'm not sure if that's correct...

[Rich-Harris]

Ah, yep. Attributes are case-sensitive on everything except regular (non-custom) HTML elements IIUC, so the check should probably be that instead.

Looking more closely at some compiled output I wonder if we should do that check inside set_attributes? Opened #15443 to compare

[Rich-Harris]

merged #15443, so I'll close this PR