npm run package stucks when there's a component with <style lang="sass">

[anafro]

Describe the bug

I try to npm run package, and it stucks if there are components in /src/lib that contains <style lang="sass">:

PS D:\tools\ui> npm run package

> @anfr/[email protected] 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

If I remove all the components with sass style tag, it gets built. For example, if we leave just Box.svelte and Text.svelte which don't have sass styles inside.

If there is a <style> tag (without lang attribute), it gets built.

// svelte.config.js
import adapter from '@sveltejs/adapter-auto';
import { vitePreprocess } from '@sveltejs/vite-plugin-svelte';

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

	kit: {
		// adapter-auto only supports some environments, see https://svelte.dev/docs/kit/adapter-auto for a list.
		// If your environment is not supported, or you settled on a specific environment, switch out the adapter.
		// See https://svelte.dev/docs/kit/adapters for more information about adapters.
		adapter: adapter()
	}
};

export default config;

// vite.config.ts
import { sveltekit } from '@sveltejs/kit/vite';
import { defineConfig } from 'vite';

export default defineConfig({
	plugins: [sveltekit()],
});

The package.json content:

{
	"name": "@anfr/ui",
	"version": "1.0.0",
	"description": "The Svelte component library for Anafro tools",
	"keywords": [
		"svelte",
		"svelte-components",
		"svelte-component-library",
		"ui",
		"ui-components",
		"anafro",
		"anafro-tools"
	],
	"homepage": "https://github.com/anafro/ui",
	"author": {
		"name": "Anatoly Frolov",
		"email": "[email protected]",
		"url": "https://anafro.ru"
	},
	"scripts": {
		"dev": "vite dev",
		"build": "vite build && npm run package",
		"preview": "vite preview",
		"package": "svelte-kit sync && svelte-package && publint",
		"prepublishOnly": "npm run package",
		"check": "svelte-kit sync && svelte-check --tsconfig ./tsconfig.json",
		"check:watch": "svelte-kit sync && svelte-check --tsconfig ./tsconfig.json --watch"
	},
	"files": [
		"dist",
		"!dist/**/*.test.*",
		"!dist/**/*.spec.*"
	],
	"sideEffects": [
		"**/*.css"
	],
	"svelte": "./dist/index.js",
	"types": "./dist/index.d.ts",
	"type": "module",
	"exports": {
		".": {
			"types": "./dist/index.d.ts",
			"svelte": "./dist/index.js"
		}
	},
	"peerDependencies": {
		"svelte": "^5.0.0"
	},
	"devDependencies": {
		"@sveltejs/adapter-auto": "^3.3.1",
		"@sveltejs/kit": "^2.11.1",
		"@sveltejs/package": "^2.3.7",
		"@sveltejs/vite-plugin-svelte": "^5.0.2",
		"publint": "^0.2.12",
		"sass-embedded": "^1.83.0",
		"svelte": "^5.12.0",
		"svelte-check": "^4.1.1",
		"typescript": "^5.7.2",
		"vite": "^6.0.3"
	},
	"dependencies": {
		"npm-check-updates": "^17.1.11",
		"svelte-preprocess-sass": "^2.0.1"
	}
}

Reproduction

https://github.com/anafro/ui

Logs

(none)

System Info

System:
    OS: Windows 11 10.0.22631
    CPU: (12) x64 Intel(R) Core(TM) i7-9750H CPU @ 2.60GHz
    Memory: 1.01 GB / 7.88 GB
  Binaries:
    Node: 20.16.0 - C:\Program Files\nodejs\node.EXE
    npm: 10.8.1 - C:\Program Files\nodejs\npm.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: ^2.11.1 => 2.11.1
    @sveltejs/package: ^2.3.7 => 2.3.7
    @sveltejs/vite-plugin-svelte: ^5.0.2 => 5.0.2
    svelte: ^5.12.0 => 5.12.0
    vite: ^6.0.3 => 6.0.3

Severity

blocking all usage of SvelteKit

Additional Information

(none)

[anafro]

I also tried to create a new project, created a component with lang="sass" styles, did the npm install -D sass-embedded, and it fails to package: the packaging process is frozen. The last line shown is: src\lib -> dist. And it never goes away

I think you can reproduce this issue this way

[anafro]

Temporary Fix

Replace vitePreprocess() with sveltePreprocess({ sass: true }) in Svelte config.