Language-tools: Unused export property warning is on the wrong line when using the TypeScript pre-processor.

Try update your @tsconfig/svelte to lastest

I am not using that.
Added it temporarily, did nothing.

Oh I thought you were using the official template. The package is a base config for svelte. You can update the extends of your tsconfig.json to match this.
https://github.com/sveltejs/template/blob/8194bf8f6452f8117195bf304ac99b15d329fbb3/scripts/setupTypeScript.js#L87

Duplicate of #333

@jasonlyu123 As i said, i added the base config temporarily but nothing changed. I still get the errors on the wrong line.

Then can you try run tsc to compile a ts file in your workspace and see if the output file has sourcemap?

The problem is with sourcemap. We use the svelte compiler to get svelte diagnostics. if you have a svelte.config.js and specify your preprocessor in it we would use that to preprocess, other than that we'll use the official svelte-preprocess. And if the preprocessor doesn't return a sourcemap the warning would be in a wrong position.

Also, we don't monitor change in the tsconfig.json so make sure you restart the language server after any changes.

It does not always generate source maps. If i call tsc on a single file it apparently does not load the tsconfig; if i use tsc -p . or tsc --build tsconfig.json it will output the source map as expected.

Can I take a look at your svelte.config.js if you have it, also which preprocessor do you use?

I use the default processor, which should be svelte-preprocess in auto mode. I made a minimal example repository which has the errors on the input component.

I tried creating a svelte.config.js, explicitly setting the pre-processor in auto mode, did not matter. Explicitly using only the typescript one with a path to the tsconfig.json did not do anything either.

Ummm... this is unexpected, it would only work when I also set sourcemap to true in tsconfig.json

Then the extends does not quite work. Well, i do not mind setting that explicitly for now.
Thanks

Yeah, I have a quick look at the source file of the svelte-preprocess. It looks like it doesn't parse the extends.
Thanks for the issue!

I opened this issue over at svelte-preprocess, because according to the docs, in auto-preprocessing mode, source maps should be generated. Update: The docs were wrong, so you need to set that to true yourself.

@brunnerh if you remove "sourceMaps": true and the base config reference from your tsconfig.json and instead do sveltePreprocess({sourceMap: true}) in your svelte.config.js, does it show the warnings at the correct line then?

@brunnerh if you remove "sourceMaps": true and the base config reference from your tsconfig.json and instead do sveltePreprocess({sourceMap: true}) in your svelte.config.js, does it show the warnings at the correct line then?

No, still off.

So it only works if you add "sourceMaps": true to the tsconfig.json?

Yes

Closing as these are problems related to svelte-preprocess. The "source map is not applied when I tell preprocess through its sourceMap-option"-problem is fixed in the latest version. The "extends-feature of tsconfig.json not supported" is tracked in https://github.com/sveltejs/svelte-preprocess/issues/300 .