breaking: deprecate SvelteComponentTyped, add generics to SvelteComponent

[dummdidumm]

Breaking change / how to migrate

SvelteComponent now has the same capabilities as SvelteComponenTyped, which is therefore now deprecated. Use SvelteComponent where you've used SvelteComponentTyped previously:

- import { SvelteComponentTyped } from 'svelte';
+ import { SvelteComponent } from 'svelte';

- export class Foo extends SvelteComponentTyped<{ aProp: string }> {}
+ export class Foo extends SvelteComponent<{ aProp: string }> {}

In case you've used SvelteComponent previously to type "I expect a Svelte component constructor here" by using typeof SvelteComponent, you'll now likely get a somewhat opaque TypeScript error.

Code:

import type { SvelteComponent } from 'svelte';

const a: typeof SvelteComponent = SomeSvelteComponentWithAProp;

Error:

Type 'typeof SomeSvelteComponentWithAProp' is not assignable to type 'typeof SvelteComponent'.
  Types of construct signatures are incompatible.
    Type 'new (options: ComponentConstructorOptions<{ prop: string; }>) => SomeSvelteComponentWithAProp' is not assignable to type 'new <Props extends Record<string, any> = any, Events extends Record<string, any> = any, Slots extends Record<string, any> = any>(options: ComponentConstructorOptions<Props>) => SvelteComponent<...>'.
      Types of parameters 'options' and 'options' are incompatible.
        Type 'ComponentConstructorOptions<Props>' is not assignable to type 'ComponentConstructorOptions<{ prop: string; }>'.
          Type 'Props' is not assignable to type '{ prop: string; }'.
            Property 'prop' is missing in type 'Record<string, any>' but required in type '{ prop: string; }'.

The solution is to either add <any> to typeof SvelteComponent (which is possible since TypeScript version 4.7) or do ComponentType<SvelteComponent> instead:

import type { SvelteComponent, ComponentType } from 'svelte';

// either
const a: typeof SvelteComponent<any> = SomeSvelteComponentWithAProp;
// or
const b: ComponentType<SvelteComponent> = SomeSvelteComponentWithAProp;

PR description

Deprecate SvelteComponentTyped, add generics to SvelteComponent - reverts the revert in #5738. Also add data- attribute to HTMLAttributes (for sveltejs/language-tools#1825) and use available TS interfaces.

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.

Tests

• Run the tests with npm test and lint the project with npm run lint

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[baseballyama]

Can we remove SvelteComponentTyped completely if we will release this PR in Svelte4 because this is a major version up?

[dummdidumm]

We could but I think it's better to do that in Svelte 5 to give people time to gracefully update their code. Also if some use components built for Svelte 3 which you can otherwise use in Svelte 4 we shouldn't block that just because the class was removed. Right now svelte package uses SvelteCompentTyped in the generated d.ts files.