What causes "some" to be undefined in vite-plugin-sveltekit-compile?

[cascading-jox]

I am trying to build a svelte component as an es module using vite library mode but I can't make it build. It feels like I am missing something basic.

This is the error:

✓ built in 209ms
[vite-plugin-sveltekit-compile] Cannot read properties of undefined (reading 'some')
✓ built in 569ms
error during build:
TypeError: Cannot read properties of undefined (reading 'some')
    at Object.handler (file:///Users/cascading-jox/Coding/vite-bug/node_modules/.pnpm/@[email protected]_@[email protected][email protected][email protected]/node_modules/@sveltejs/kit/src/exports/vite/index.js:749:38)
    at process.processTicksAndRejections (node:internal/process/task_queues:95:5)
    at async PluginDriver.hookParallel (file:///Users/cascading-jox/Coding/vite-bug/node_modules/.pnpm/[email protected]/node_modules/rollup/dist/es/shared/node-entry.js:18561:17)
    at async file:///Users/cascading-jox/Coding/vite-bug/node_modules/.pnpm/[email protected]/node_modules/rollup/dist/es/shared/node-entry.js:19559:13
    at async catchUnfinishedHookActions (file:///Users/cascading-jox/Coding/vite-bug/node_modules/.pnpm/[email protected]/node_modules/rollup/dist/es/shared/node-entry.js:18983:16)
    at async build (file:///Users/cascading-jox/Coding/vite-bug/node_modules/.pnpm/[email protected]/node_modules/vite/dist/node/chunks/dep-R0I0XnyH.js:66815:22)
    at async CAC.<anonymous> (file:///Users/cascading-jox/Coding/vite-bug/node_modules/.pnpm/[email protected]/node_modules/vite/dist/node/cli.js:845:9)
 ELIFECYCLE  Command failed with exit code 1.

This is my vite.config.js file:

import { sveltekit } from '@sveltejs/kit/vite';
import { defineConfig } from 'vite';
import { resolve } from 'path';

export default defineConfig({
    build: {
        lib: {
            // Could also be a dictionary or array of multiple entry points
            entry: resolve(__dirname, 'lib/index.js'),
            name: 'Test',
            // the proper extensions will be added
            fileName: 'test',
            formats: ['es']
        }
    },
    plugins: [sveltekit()]
});

And this is my index.js file:

// Reexport your entry components here
import Test from './Test.svelte';
export { Test };

Link to reproducible example.

Link to stackoverflow issue.

Any help is much appreciated!

[mootoday]

Uh no, I ended up here because I have the same issue and saw Unanswered 😅. @cascading-jox have you ever figured out what caused it?

[cascading-jox]

Nope, just went with rollup instead.

[HriGunov]

I was had the same issue a while back, subscribed to the discussion. A few months ago I found the solution, but forgot to share.

You have to use the svelte plugin when you want to get a js bundle.

- import { sveltekit } from '@sveltejs/kit/vite';
+ import { svelte } from '@sveltejs/vite-plugin-svelte';
import { defineConfig } from 'vite';

export default defineConfig({
        ...
	plugins: [
-	    sveltekit()
+            svelte()
	],
	...
});

I use 2 separate vite configs. The first one (uses thesveltekit plugin), for messing around and developing custom components. The other one (uses the svelte plugin) bundles everything in to a single bundles, I run this on a each component separately so I can import only the components I need.

For a reference, in case I am missing something. Here is the Vite config and command that I use to build components in to separate bundles.

> vite build -c [path-to-build-vite-config] -- --component-input [path-to-your component]

import { svelte } from '@sveltejs/vite-plugin-svelte';
import { type BuildOptions } from 'vite';
import { defineConfig } from 'vitest/config';
import fs from 'fs';

export default defineConfig(() => {
	const args = process.argv;

	if (!args.includes('--component-input')) {
		throw new Error('Missing --component-input argument');
	}

	let inputFile: string | string[] = args[args.indexOf('--component-input') + 1];

	if (!fs.existsSync(inputFile)) {
		throw new Error(`File ${inputFile} does not exist`);
	}

	return {
		plugins: [svelte()],
		resolve: { alias: { $lib: '/src/lib' } },
		build: {
			outDir: 'dist',
			rollupOptions: {
				input: inputFile,
				output: {
					format: 'umd',
					entryFileNames: '_[name].wc.js'
				}
			} as BuildOptions['rollupOptions'],
			emptyOutDir: false
		},
		test: {
			include: ['src/**/*.{test,spec}.{js,ts}']
		}
	};
});