Allow usage of `svelte.config.ts`

[jnoordsij]

Description

Per sveltejs/kit#13935 loading svelte.config.ts is supported. However, when I use such a file in my project it seems to be undetected by both my IDE tooling and when running svelte-check.

Proposed solution

A quick look lead me to this:

language-tools/packages/language-server/src/lib/documents/configLoader.ts

Lines 222 to 225 in 2c99c58

	const config =
	this.tryGetConfig(file, currentDir, 'js') ||
	this.tryGetConfig(file, currentDir, 'cjs') ||
	this.tryGetConfig(file, currentDir, 'mjs');

I suspect altering this is a requirement for compatibility, but may not be sufficient. I have not yet had any time to dive into this further, so any assistance is welcome.

Alternatives

No response

Additional Information, eg. Screenshots

Edit: progress on resolving this can be found at #2804.

[konstantinblaesi]

What errors do you get? For me it seems to work when running commands with NODE_OPTIONS e.g.
NODE_OPTIONS=--experimental-strip-types npx vite dev

[Alex6357]

What errors do you get? For me it seems to work when running commands with NODE_OPTIONS e.g. NODE_OPTIONS=--experimental-strip-types npx vite dev

Vite works out of the box. However, svelte-check seems to ignore svelte.config.ts and print message like Parsing xxx.svelte failed. No preprocess config found but lang tag exists. Skip showing error because they likely use other preprocessors. when using <script lang="ts"> (though it still checks ts errors).

[jasonlyu123]

There is a PR #2804 for adding the support. But it's not ready yet.

[jnoordsij]

There is a PR #2804 for adding the support. But it's not ready yet.

Ah thanks for pointing me there, I could not find this when searching for svelte.config.ts specifically, that's my bad!

Great to see this is being actively worked on.

[DarthGigi]

Has there been any news about the state of this yet? Trying to use async svelte and remote functions but since the project uses svelte.config.ts the language tools fails to read the config file and gives the following error:

Cannot use `await` in deriveds and template expressions, or at the top level of a component, unless the `experimental.async` compiler option is `true`
https://svelte.dev/e/experimental_async svelte(experimental_async)

Not a big deal to switch to .js for the time being but it would be great to have .ts support