Component.svelte

<script lang="ts">
  export let name = 'World'
</script>

<div>Hello {name}</div>

error

Uncaught Error: 'target' is a required option
    at new SvelteComponentDev (index.mjs?v=9205789b:1666)

External.svelte

<script lang="ts">
  import { Component, helper } from "../../dist/component.es";
  
  let name = "Friend"
</script>

<Component {name} />

index.ts

import Component from './Component.svelte'
import { helper } from './helper'

export {
  Component,
  helper
}

vite.config.js

import { defineConfig } from 'vite'
import svelte from '@sveltejs/vite-plugin-svelte'

export default defineConfig({
  plugins: [svelte()],
  build: {
    lib: {
      entry: 'src/lib/index.ts',
      name: 'Component',
    },
    rollupOptions: {
      external: ['svelte'],
    }
  }
})