Support for array of preprocessors

[itsMapleLeaf]

Describe the bug
import type syntax causes a type error. This is needed for ESM-sensitive bundlers that need to differentiate types from values for erasure during compilation

To Reproduce
Steps to reproduce the behavior:

// svelte.config.js
const preprocess = require("svelte-preprocess")

module.exports = {
	preprocess: [
		preprocess.postcss(),
		preprocess.typescript({ transpileOnly: true }),
	],
}

// types.ts
export type Secret = string

<!-- Component.svelte -->
<script lang="ts">
  import type { Secret } from './types' // type error on this line
  const secret: Secret = '42'
</script>

For example a code snippet that is treated in a way you don't expect.

Expected behavior
Type imports should be parsed without errors

Screenshots
If applicable, add screenshots to help explain your problem.

System (please complete the following information):

• OS: Windows 10
• IDE: VSCode
• Plugin/Package: Svelte for VSCode

[dummdidumm]

I think it's because you use an array of preprocessors, that is not supported yet.
If you refactor your svelte.config.js to

const preprocess = require("svelte-preprocess")

module.exports = {
	preprocess: preprocess({
                postcss: true,
		typescript: { transpileOnly: true }
        }),
}

does it work then?

[itsMapleLeaf]

That indeed fixes it, thanks 😅 maybe a note in the docs would be helpful?

[dummdidumm]

Absolutely

[kevmodrome]

What would be needed for this to be supported? Willing to help any way I can! Not having this feature makes it impossible to use MDSveX and sass together, for example

[dummdidumm]

I think @kaisermann wanted to take a shot at this, not sure what his status on that is though.

[kaisermann]

@dummdidumm I've stopped what I was doing a while ago, but will probably get back to it tomorrow or this weekend!