[feat] add convenience types ComponentType and ComponentProps

[dummdidumm]

Eases typing "this is a variable that expects a Svelte component constructor (of a certain shape)". Removes the need for SvelteComponentTyped to be an extra type so it can be deprecated in v4 and removed in v5, and SvelteComponent(Dev) can receive the same generic typings as SvelteComponetTyped in v4.

Also add ComponentProps to get the props a component expects (fixes #7584)

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

[dummdidumm]

Seems we need to bump the TypeScript version as it's too old to use the new type modifier. If I don't add it, the export is not stripped and it's a runtime error.

[dummdidumm]

I ended up bumping TS, acknowledging the fact that it may introduce accidentally adding type syntax later that is incompatible with TS 3.7 . Doing so technically is a breaking change, although I doubt that anyone is using a TS version this old, especially since everyone using TS with Svelte is required to use a newer version of TS. But because it's a breaking change, I decided to add a short script which rewrites the new type syntax to something valid in 3.7 . @Conduitry hope this is okay for you.

[Conduitry]

especially since everyone using TS with Svelte is required to use a newer version of TS

@dummdidumm Required by what? SvelteKit? Other tooling?

Is this a breaking change only insofar as someone might be manually interacting with the types using an old version of the TS compiler, separately from what any of the official tooling is already doing?

[dummdidumm]

It's a breaking change for everyone who uses an old TS version which does not understand the export type syntax that would be introduced by this PR, if the postbuild script wouldn't exist. Not exactly sure in what way it would break though (no more intellisense, module typed as any, I don't know). As soon as you use Svelte with TS and import from svelte the break would occur.

[dummdidumm]

I updated the PR and adjusted the code. I switched out SvelteComponentConstructor with ComponentType which provides more flexibility (you can also use it to get the constructor type of an existing component) and is easier to grok in my opinion. I also adjusted the type generation code so that the TS bump is no longer needed.

@ivanhofer @ignatiusmb could you have a look at this? More specifically:

• names of these convenience types good?
• docs understandable?
• actually helpful convenience types?

[ivanhofer]

Nice additions of useful type helpers.
The tsd.js is a smart way to bypass the failing types 👏

[ivanhofer]

This file exports an interface SvelteComponentDev and a class with the same name. The types of the interface and the class don't match. It was not added in this PR but I find it confusing.

[ivanhofer]

also not part of this PR but wouldn't it be better to combine SvelteComponentDev and SvelteComponentTyped. Currently SvelteComponentTyped is just SvelteComponentDev with some generics that all contain default parameters. When not adding any generics this should result into the same type as SvelteComponentDev

[ignatiusmb]

This would be a nice addition to the Svelte + TS integration when it gets in!