Cannot redefine property: fetch

[GauBen]

Describe the bug

I'm trying to import a built svelte-kit site within another one, and it is not possible because importing import { handler } from 'sub-site/build/handler' has side-effects, namely calling __fetch_polyfill.

Reproduction

1. Create a svelte-kit website that uses adapter-node
2. Build this website
3. Create another svelte-kit website with the following configuration

import adapter from '@sveltejs/adapter-node'
import preprocess from 'svelte-preprocess'
import { handler } from 'sub-site/build/handler'

/** @type {import('@sveltejs/kit').Config} */
const config = {
  preprocess: preprocess(),
  kit: {
    adapter: adapter(),
    target: '#svelte',
    vite: {
      plugins: [
        {
          name: 'sub-site',
          configureServer({ middlewares }) {
            middlewares.use(handler) // Load the sub-site here
          },
        },
      ],
    },
  },
}

export default config

Logs

> Cannot redefine property: fetch
    at Function.defineProperties (<anonymous>)
    at __fetch_polyfill (file:///home/.../node_modules/.pnpm/@sveltejs+kit@1.0.0-next.229_svelte@3.46.1/node_modules/@sveltejs/kit/dist/install-fetch.js:6494:9)

System Info

SvelteKit v1.0.0-next.229
Adapter Node v1.0.0-next.61

Severity

annoyance

Additional Information

I'll submit a PR in a few minutes that fixes this issue, the solution is to add configurable: true to all definitions here:

kit/packages/kit/src/install-fetch.js

Lines 4 to 23 in f92c3e2

	export function __fetch_polyfill() {
	Object.defineProperties(globalThis, {
	fetch: {
	enumerable: true,
	value: fetch
	},
	Response: {
	enumerable: true,
	value: Response
	},
	Request: {
	enumerable: true,
	value: Request
	},
	Headers: {
	enumerable: true,
	value: Headers
	}
	});
	}

[GauBen]

@Rich-Harris Could you please bump adapter-node to use kit v231?

[bluwy]

#3357 that fixes this has been merged. Closing this.

Could you please bump adapter-node to use kit v231?

I'm not sure what you mean. adapter-node doesn't have a hard version on kit?

[GauBen]

I'm not sure what you mean. adapter-node doesn't have a hard version on kit?

That's right, but since adapter-node was built and published before #3357 was merged, the dist still contains the old __fetch_polyfill.

[bluwy]

Ah I see. Looks like adapter vercel, node and netlify builds based on kit. I'll make a changeset for them so they get re-released. (#3377)