feat: attachments fromAction utility

[paoloricciuti]

This provides a way to convert from action to attachments...this is useful if you are using a library that provides actions (like melt) and you want to spread them in dumb components.

<script>
	import Button from "./Button.svelte";
	import { log } from "log-my-number";
	import { fromAction } from "svelte/attachments";
	let count = $state(0);
</script>
<Button
	onclick={() => count++}
	{@attach fromAction(log, () => count)}
>
	{count}
</Button>

There's a slight type issue at the moment: if you have an optional argument to the action you will need to pass the second argument... I was not able to fix this yet but since I'm not sure if this will actually be merged I decided to put it out there to discuss and maybe someone better than me at TS will be able to fix it (or I'll fix it later since i have to go now)

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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: 5a18de2

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

This PR includes changesets to release 1 package

Name	Type
svelte	Minor

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[svelte-docs-bot]

Preview: https://svelte-dev-git-preview-svelte-15933-svelte.vercel.app/

[github-actions]

Playground

pnpm add https://pkg.pr.new/svelte@15933

[JonathonRP]

Could this be achieved in user land too?

[paoloricciuti]

Could this be achieved in user land too?

Totally, in fact if we decide it's not good for core I'm gonna open a PR for runed

[JonathonRP]

So with this does the action run in effect still or preserved behavior of not running in effect? I tried migrating to using attachment but seems broken as mine was relying on being run server side or like pre?

[paoloricciuti]

So with this does the action run in effect still or preserved behavior of not running in effect? I tried migrating to using attachment but seems broken as mine was relying on being run server side or like pre?

That's weird because actions don't run on the server either 😁

[JonathonRP]

That's weird because actions don't run on the server either 😁

Where do actions run than? 🤔

[paoloricciuti]

That's weird because actions don't run on the server either 😁

Where do actions run than? 🤔

On the client, as soon as an element is mounted

[JonathonRP]

On the client, as soon as an element is mounted

Are attachments run the same way then?

[paoloricciuti]

They are but are run within an effect so everything reactive you "pass" to them will make the attachment rerun