Importing `server_manager.svelte.ts` that is put under `$lib` triggered error about information leak

[chenzhekl]

Describe the bug

Importing the file $lib/server_manager.svelte.ts into client pages triggered error

[vite] Internal server error: Cannot import $lib/server_manager.svelte.ts into client-side code. This could leak sensitive information.

This is super frustrating. Why did server_manager made SvelteKit believe it was an server only file?

Reproduction

Create a new SvelteKit project. Create an file server_manager.svelte.ts in /src/lib. Import anything in $lib/server_manager.svelte.ts into client codes.

Logs

System Info

System:
    OS: Linux 5.15 Ubuntu 24.04.2 LTS 24.04.2 LTS (Noble Numbat)
    CPU: (24) x64 12th Gen Intel(R) Core(TM) i9-12900K
    Memory: 53.39 GB / 62.58 GB
    Container: Yes
    Shell: 5.2.21 - /bin/bash
Binaries:
    Node: 22.17.1 - /opt/node/bin/node
    npm: 10.9.2 - /opt/node/bin/npm

Severity

annoyance

Additional Information

No response

[Conduitry]

Sounds like a bug in the check for $lib/server/.... https://svelte.dev/docs/kit/server-only-modules#Your-modules

[Rich-Harris]

Noting also that we currently — incorrectly — regard $lib/server.ts as server-only (it should be *.server.ts and $lib/server/**). I think we should probably fix this in SvelteKit 3, and warn in the meantime that it will change if that file exists

[Rich-Harris]

(I changed my mind, I don't think we need to treat $lib/server.ts any differently than $lib/server_whatever.ts — both handled in #14191)