`svelte-check`: Doesn't flag TS2614 about exporting snippets from .svelte files, but TypeScript does

[webJose]

Describe the bug

Given a .svelte file that exports snippets:

<script lang="ts" module>
    import Children1Col from "$lib/tests/Children1Col.svelte";
    import ChildrenEmptyCell from "$lib/tests/ChildrenEmptyCell.svelte";

    export { children1Col, childrenEmptyCell };
</script>

{#snippet children1Col()}
    <Children1Col />
{/snippet}

{#snippet childrenEmptyCell()}
    <ChildrenEmptyCell />
{/snippet}

And later importing one of them:

import { children1Col } from '$lib/tests/TestSnippets.svelte';

Makes TypeScript flag the statement with TS2614:

That's fine, I guess. I believe this happens because of the ambient module for *.svelte. We cannot predict that a particular .svelte file will export something out of the module script. So I proceed to use // @ts-expect-error. That makes the error goes away.

However, svelte-check says:

Error: Unused '@ts-expect-error' directive. 
import Layout from '$lib/tests/Layout.svelte';
// @ts-expect-error TS2614
import { children1Col } from '$lib/tests/TestSnippets.svelte';

So I can make TypeScript happy, or svelte-check happy. I cannot make both happy.

Reproduction

See previous section.

Expected behaviour

svelte-check and TypeScript should be in accordance with each other.

System Info

• OS: Windows
• IDE: VS Code
• Svelte for VS Code version: 110.3.0

Which package is the issue about?

svelte-check

Additional Information, eg. Screenshots

No response

[jasonlyu123]

This is most likely because you're using TypeScript 7 in your editor. If you're using it, you'll see this warning during extension startup.

And it'll also be indicated in the status bar at the bottom right corner.

Another possibility is that you didn't have the typescript-plugin enabled. This is needed for TypeScript to recognise named exports from Svelte files. This is also the reason why it has the error if you're using TypeScript 7. It currently doesn't have an equivalent API,

[webJose]

I do have TypeScript v7 in some repos. I always install locally. Are you saying that maybe I have TypeScript v7 installed globally? I do get the notification you show in the first window.

I don't upgrade my Svelte projects to TypeScript v7, though. How can I revert this situation?

[jasonlyu123]

It seems like VSCode or the TypeScript 7 extension has a detection to automatically enable TypeScript 7. It'll use the binary bundled with the TypeScript 7 extension. But I haven't figured out how exactly it does it. You can set the "js/ts.experimental.useTsgo": false config in your workspace settings.json to disable it.

[webJose]

Your tip works. Thank you very much! I guess this wasn't a bug, after all. Feel free to close.