svelte-package hangs after finish

[thebjorn]

Describe the bug

If you forget to edit svelte.config.js, changing vitePreprocess() to sveltePreprocess({scss: true}), svelte-package will hang forever after printing src\lib -> dist.

Reproduction

I've created a repo from sv create that followed the steps below (except, of course, I didn't update svelte.config.js since that exhibits the problem).

Steps to reproduce:

sv create svelte-sasshang
cd svelte-sasshang
pnpm up

Add src/lib/Foo.svelte (note the lang="scss")

<script>
    let { foo } = $props();
</script>

<div> {foo} </div>

<style lang="scss">
    div { color: red; }
</style>

run

pnpm build

build gives a helpful error messag:

> Preprocessor dependency "sass-embedded" not found. Did you install it? Try `pnpm add -D sass-embedded`.
    at loadPreprocessorPath (file:///C:/srv/work/svelte-sasshang/node_modules/.pnpm/vite@6.0.3/node_modules/vite/dist/node/chunks/dep-yUJfKD1i.js:48754:13)
    at loadSassPackage (file:///C:/srv/work/svelte-sasshang/node_modules/.pnpm/vite@6.0.3/node_modules/vite/dist/node/chunks/dep-yUJfKD1i.js:48769:19)
    at process (file:///C:/srv/work/svelte-sasshang/node_modules/.pnpm/vite@6.0.3/node_modules/vite/dist/node/chunks/dep-yUJfKD1i.js:49034:27)
    at compileCSSPreprocessors (file:///C:/srv/work/svelte-sasshang/node_modules/.pnpm/vite@6.0.3/node_modules/vite/dist/node/chunks/dep-yUJfKD1i.js:48168:34)
    at compileCSS (file:///C:/srv/work/svelte-sasshang/node_modules/.pnpm/vite@6.0.3/node_modules/vite/dist/node/chunks/dep-yUJfKD1i.js:48226:38)
    at async preprocessCSS (file:///C:/srv/work/svelte-sasshang/node_modules/.pnpm/vite@6.0.3/node_modules/vite/dist/node/chunks/dep-yUJfKD1i.js:48451:10)
    at async style (file:///C:/srv/work/svelte-sasshang/node_modules/.pnpm/@sveltejs+vite-plugin-svelte@5.0.1_svelte@5.9.0_vite@6.0.3/node_modules/@sveltejs/vite-plugin-svelte/src/preprocess.js:77:31)
    at async process_single_tag (file:///C:/srv/work/svelte-sasshang/node_modules/.pnpm/svelte@5.9.0/node_modules/svelte/src/compiler/preprocess/index.js:283:21)
    at async Promise.all (index 0)
    at async replace_in_code (file:///C:/srv/work/svelte-sasshang/node_modules/.pnpm/svelte@5.9.0/node_modules/svelte/src/compiler/preprocess/replace_in_code.js:70:23)
 ELIFECYCLE  Command failed with exit code 1.

add sass-embedded:

pnpm add -D sass-embedded

run pnpm build again.
svelte-package hangs forever.

> svelte-sasshang@0.0.1 package
> svelte-kit sync && svelte-package && publint

If bundling, conditions should include development or production. If not bundling, conditions or NODE_ENV should include development or production. See https://www.npmjs.com/package/esm-env for tips on setting conditions in popular bundlers and runtimes.
src\lib -> dist

The problem is that you need to change svelte.config.js:

import adapter from '@sveltejs/adapter-auto';
- import { vitePreprocess } from '@sveltejs/vite-plugin-svelte';
+ import { sveltePreprocess } from 'svelte-preprocess';

/** @type {import('@sveltejs/kit').Config} */
const config = {
	// Consult https://svelte.dev/docs/kit/integrations
	// for more information about preprocessors
- 	preprocess: vitePreprocess(),
+ 	preprocess: sveltePreprocess({scss: true}),
    ...

Logs

see above

System Info

System:
    OS: Windows 11 10.0.22631
    CPU: (48) x64 AMD Ryzen Threadripper 3960X 24-Core Processor
    Memory: 32.29 GB / 63.88 GB
  Binaries:
    Node: 22.6.0 - C:\Program Files\nodejs\node.EXE
    Yarn: 1.22.21 - ~\AppData\Roaming\npm\yarn.CMD
    npm: 10.9.0 - C:\Program Files\nodejs\npm.CMD
    pnpm: 9.14.4 - ~\AppData\Local\pnpm\pnpm.CMD
    bun: 1.1.8 - ~\AppData\Roaming\npm\bun.CMD
  Browsers:
    Edge: Chromium (127.0.2651.74)
    Internet Explorer: 11.0.22621.3527
  npmPackages:
    @sveltejs/adapter-auto: ^3.3.1 => 3.3.1
    @sveltejs/kit: ^2.9.0 => 2.9.0
    @sveltejs/package: ^2.3.7 => 2.3.7
    @sveltejs/vite-plugin-svelte: ^5.0.1 => 5.0.1
    svelte: ^5.9.0 => 5.9.0
    vite: ^6.0.3 => 6.0.3

Severity

annoyance

Additional Information

It would be great if it gave an error message instead of hanging (it was very difficult to isolate).

If sv could add scss and take care of such things it would be super-cool ;-)

[webJose]

What I have noticed is that killing dart.exe releases the block. Sass is now using Dart for their executables.

[thebjorn]

I can confirm that killing dart.exe often fixes hanging problems ;-)

[EAlexis92]

Cant kill a process when you are deploying. Please fix this!