fix: distinct memoizer on style/class directives

[adiguba]

Fix #18465

The style and classe directives are generated using an unique memoizer for all the class/style directive :

For example, this :

<div style:color={color()} style:background={background()} style:font-size={size}></div>

Will generate something like this :

	let styles;

	$.template_effect(($0) => styles = $.set_style(div, '', styles, $0), [
		() => ({
			color: color(),
			background: background(),
			'font-size': $$props.size
		})
	]);

=> This implies that all the function call will be executed again when a reactivity change occurs.

The patch change the behavior, by using the memoizer for each indiviually directive :

	let styles;

	$.template_effect(($0, $1) => styles = $.set_style(div, '', styles, { color: $0, background: $1, 'font-size': $$props.size }), [
		() => color(),
		() => background()
	]);

Note :

• This also fix some potential await_reactivity_loss when used with an async function.
• The object properties are re-build on each update. Didn't known if this can have an impact on performance.

Before submitting the PR, please make sure you do the following

• It's really useful if your PR references an issue where it is discussed ahead of time. In many cases, features are absent for a reason. For large changes, please create an RFC: https://github.com/sveltejs/rfcs
• Prefix your PR title with feat:, fix:, chore:, or docs:.
• This message body should clearly illustrate what problems it solves.
• Ideally, include a test that fails without this PR but passes with it.
• If this PR changes code within packages/svelte/src, add a changeset (npx changeset).

Tests and linting

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

Note : I launch the tests without errors, but npx changeset and pnpm lint produce an error with prettier-plugin-svelte@3.4...

[changeset-bot]

🦋 Changeset detected

Latest commit: 8fd1500

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

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[svelte-docs-bot]

Preview: https://svelte-dev-git-preview-svelte-18466-svelte.vercel.app/

[github-actions]

Playground

pnpm add https://pkg.pr.new/svelte@18466

[pkg-svelte-dev]

Install the latest version of svelte from 8fd1500:

pnpm add https://pkg.svelte.dev/svelte/c/8fd15004520998b27753ac76646177a0a7824f26

Open in pkg.svelte.dev: https://pkg.svelte.dev/repos/svelte/pr/18466

[adiguba]

I fixed the lint error and added changeset.

Also, an example of the error when using await on style: directive :

https://svelte.dev/playground/hello-world?version=5.56.4#H4sIAAAAAAAACm2QQWuEMBCF_0oYelCQ7vZqVeih0GOhe6s9ZJNxNzROJBm1Iv73knWLC91TyPsyk_feDCRbhBze0FonRuetFglqw6hTyKAxFgPknzPw1MV3UYDsb-ql6x7DgJajdpQB7-nKESNxgByKoLzpuKqpZhkmUqLpSbFxJE7Iylnnk1TMEdcsR2lYEI7i3bvWBEy8KCsRkA-mRddz4jPxtN-n6fM64JF7T6IGj7qGi7jUFA-LLI5SfZ-860mLUjwEloxJDVPMPdZw3UHFbrNIRUCLisXRkM4HaXss523NcolRuC76r8azYSx219stsaa9D9a_7yI1SboLml6dg5E3rNitLlfH2gwi8GQxv7RZzmuLW7vLFW85_mc6vH4c4mJthgoyYPxhyNn3uHxlwNLY0ZCGvJE24PILufJMWUMCAAA

Same code fixed with this PR :

https://svelte.dev/playground/hello-world?version=pr-18466#H4sIAAAAAAAACm2QQWuEMBCF_0oYelCQ7vZqVeih0GOhe6s9ZJNxNzROJBm1Iv73knWLC91TyPsyk_feDCRbhBze0FonRuetFglqw6hTyKAxFgPknzPw1MV3UYDsb-ql6x7DgJajdpQB7-nKESNxgByKoLzpuKqpZhkmUqLpSbFxJE7Iylnnk1TMEdcsR2lYEI7i3bvWBEy8KCsRkA-mRddz4jPxtN-n6fM64JF7T6IGj7qGi7jUFA-LLI5SfZ-860mLUjwEloxJDVPMPdZw3UHFbrNIRUCLisXRkM4HaXss523NcolRuC76r8azYSx219stsaa9D9a_7yI1SboLml6dg5E3rNitLlfH2gwi8GQxv7RZzmuLW7vLFW85_mc6vH4c4mJthgoyYPxhyNn3uHxlwNLY0ZCGvJE24PILufJMWUMCAAA

[dummdidumm]

thank you!