Resolve problems with (group) folder

[hawk93]

Describe the bug

I found a problem while using resolve with (group) folders in the path.

Given this directory structure

src/routes/[id]/
├ (group)/
│ ├ +page.svelte
│ └ in/
│   └ +page.svelte 
└ out/
  └ +page.svelte 

You can resolve correctly "/a" calling resolve('/[id]', { id: 'a' }) or resolve('/[id]/(group)', { id: 'a' }), but you can't resolve "/a/in" without a type error if you call resolve without the (group) folder, resolve('/[id]/in', { id: 'a' }) errors out (Expected 1 arguments, but got 2), while resolve('/[id]/(group)/in', { id: 'a' }) is fine

In the reproduction there are more variants of this directory structure with the usage of optional parameters too

Reproduction

Stackblitz

Running the typecheck you see that it errors out when you pass params to the resolve function if you are trying to resolve the subfolder of a group

Logs

System Info

@sveltejs/kit: 2.26.1 
svelte: 5.37.0 
typescript: 5.8.3

Severity

annoyance

Additional Information

EDIT: Removed the second problem, I will open a separate issue for it

[PatrickG]

I think that is working as intended.
You can either pass a pathname or a route id to resolve.
/[id]/in is simply not a valid route id, so it is interpreted as a pathname.

[hawk93]

That makes sense, but the group segment doesn't affect the path created and I find easier to reason about the resolved path I expect ignoring the group.
In case the actual behavior is correct then we have two errors i think:

• resolve('/[id]', { id: 'a' }) is not erroring out, the right route id in this situation would be /[id]/(group)
• resolve('/[id]', { id: 'a' }) it's still correctly returning /a

PS I was moving from vite-plugin-kit-routes where you don't have to specify the group in the route resolution and I always find it really straightforward to reason about

[Rich-Harris]

closing per #14064 (comment)