How are extensions configured in svelte.config.js?

[webJose]

This is just a very minor thing: In VS Code, you the icon of a file changes when its filename ends with ".test.ts", versus the icon used for ".ts" files. I like it as I can identify test files visually with this icon change.

However, if I need runes in test files, it must be named with ".test.svelte.ts", because it must end with ".svelte.ts" or runes are a No No. This makes VS Code not to use the test icon. So I said "No problem, I'll just specify the extensions in svelte.config.js". Well, couldn't make it work.

I did:

const config = {
    extensions: [".svelte", ".svelte.js", ".svelte.ts", ".svelte.test.js", ".svelte.test.ts"],
   ...

With this, no testing works. For some reason a compiler error on @testing-library/svelte happens. It is super unhelpful: Unexpected token on the line where the mount function is defining the props object (to later be used in rerender()).

Any guidance on how to define the extensions properly? Am I doing this wrong?

[brunnerh]

There was an issue about this:

• Allow more flexible glob matchers for runic js/ts modules #11536

So runes in .svelte.test.js/ts should already work with most bundlers/tooling.
I don't think you should need to adjust any config if you use Vite/Rollup/Webpack and as long as the tooling is up to date.

Tooling releases that work may not be stable yet.

[dominikg]

extensions is only for svelte sfc files. you don't have to configure anything for svelte.test.js to work, just use latest vite-plugin-svelte@4

[webJose]

Really? Not working for me. I'll check the package versions once I get back to my work PC. Thanks for the input.

[webJose]

This is what I get when I rename Combobox.test.svelte.ts to Combobox.svelte.test.ts:

Conversely, the tests run fine with the unaltered file name.

As for packages, this is what I have outdated (svelte-wise):

It seems that vite-plugin-svelte version 4 doesn't exist. I am behind one patch revision. That's all. What else could I be doing wrong, if the file name should work?

[brunnerh]

It's a preview release, the latest one is 4.0.0-next.6

[webJose]

Ok, by upgrading to @sveltejs/vite-plugin-svelte v4.0.0-next.6, the error is now different:

This happens regardless of the file name.

[brunnerh]

Maybe there is an issue worth reporting there.
Can you create a minimal reproduction?

[webJose]

Yes, I suspected that much. The file is large. We do all unit testing in one file. We like this because it looks clean, but I guess it makes pinpointing this error that much harder. Don't promise I'll do it, but since I love Svelte and want it to suceed, I'll definitely try to find time to reproduce.