Shared config object is mutated

[benmccann]

Describe the bug

SvelteKit's vite/index.js stores the config in vite_user_config and passes it into multiple builds. Vite mutates the config causing unexpected values for latter builds. This doesn't seem to be an issue for most users, but does cause issues with vite-plugin-pwa

Reproduction

Update svelte.config.js for the site to the one below. Note that you need to comment out SvelteKit's process.exit for the Vite plugin to be invoked

import * as path from 'path';
import adapter from '@sveltejs/adapter-auto';
import { imagetools } from 'vite-imagetools';

let viteConfig;

/** @type {import('@sveltejs/kit').Config} */
const config = {
	kit: {
		adapter: adapter(),

		prerender: {
			default: true,
			entries: ['*', '/content.json']
		},

		vite: {
			plugins: [imagetools(), {
				name: "vite-plugin-pwa",
				enforce: "post",
				apply: "build",
				async configResolved(config) {
					viteConfig = config;
				},
				async closeBundle() {
					console.log(`IS SSR? ${viteConfig.build.ssr}`)
				}
			}],

			resolve: {
				alias: {
					$img: path.resolve('src/images')
				}
			},

			server: {
				fs: {
					strict: false
				}
			}
		}
	}
};

export default config;

Suggested Solution

The config above isn't one that can be cloned. Instead we need to do something like leave vite-plugin-svelte-kit in place, but make writeBundle a no-op unless it's the client build (or equivalently split the config stuff out into a separate plugin that's used for the server build as well)

System Info

`master`

Severity

Prevents https://github.com/userquin/pwa-sveltekit-vite from working

Additional Information

No response