(feat) make it possible to pass additional file paths to emitDts

[dummdidumm]

Needed when someone uses the svelte.JSX typings.
Closes #1405

Other possibilities:

• type this as string like in (feat) Add support for svelte-jsx.d.ts and svelte-native-jsx.d.ts to emitDts #1405 -> decided against that because it's not flexible enough for other use cases
• use require.resolve for this to get the d.ts file -> decided against that because people might use this in other environments than HTML (Svelte Native) and they couldn't pass their file in then

[dummdidumm]

Marking this as draft because different thought just occured to me:

• What if we add the ambient typings to the @types namespace? Would this be something we should do in the long run anyway?
• Is this solvable by adding another reference to the app.d.ts (/// <reference types="svelte2tsx/svelte-jsx" />, @rgossiaux does this work for you?) template in the case of SvelteKit?

cc @jasonlyu123

[rgossiaux]

• Is this solvable by adding another reference to the app.d.ts (/// <reference types="svelte2tsx/svelte-jsx" />, @rgossiaux does this work for you?) template in the case of SvelteKit?

From what I see the app.d.ts is not passed to emitDts, since it lives outside the lib/ directory, so you'd still need a config change to solve that. But regardless, anything that solves the problem works for me, I'm not picky 😃

[dummdidumm]

Oh right you're correct, that wouldn't work for you in this case. You could add a d.ts file to the lib folder with the mentioned content and exclude it from being exported, maybe that works.

[fallaciousreasoning]

Wondering if there was any movement on this, or did you end up solving this in a different way?

[fallaciousreasoning]

FWIW, I'm working on a Svelte component library, and we're compiling the Svelte components to web-components. We're using svelte2tsx to generate the type definitions which we use to get intellisense & typings in a React wrapper. This works really well for most cases, but when the component is something primitive (like a button or a link) and we want to expose the props on the underlying HTML element svelte2tsx breaks.

Currently, I have a fork of svelte2tsx with this change, which I'm vendoring into the repository and it works really nicely. Any chance we could land this? It solves this really nicely 😄

[jasonlyu123]

The plan is to move the element typing to the svelte core. You can see the roadmap here #1552

[fallaciousreasoning]

Okay, got this working without the svelte2tsx fork by bumping Svelte to 3.55.0 and using SvelteHTMLElements['button'] instead of the svelte2tsx typings. Thanks @jasonlyu123!

[dummdidumm]

Since Svelte 3.55 it's possible to enhance from HTML typings through the svelte/elements import. I think this PR might be obsolete because of this.