`process.env` undefined in service-worker.js using Rollup

Using Rollup to bundle my Sapper app, I am getting an error in service-worker.js where process.env is not defined. This doesn’t appear to be an issue using Webpack.

I sourced the code back to https://github.com/moovweb/xdn/blob/master/packages/prefetch/src/constants.ts

As a workaround, I added the references to the replace plugin based on the default values. In rollup.config.js, I have:

serviceworker: {
  input: config.serviceworker.input(),
  output: config.serviceworker.output(),
  plugins: [
      'process.browser': true,
      'process.env.NODE_ENV': JSON.stringify(mode),
      'process.env.XDN_PREFETCH_CACHE_NAME': '"prefetch"',
      'process.env.BACKEND_REQUESTS_RESPONSE_HEADER_NAME': '"x-xdn-upstream-requests"',
      'process.env.XDN_PREFETCH_HEADER_VALUE': '"1"'
    !dev && terser(),

  preserveEntrySignatures: false,

To reproduce:

npx degit "sveltejs/sapper-template#rollup" sapper-rollup
cd sapper-rollup
npm i
xdn init

Add the following to service-worker.js:

/* begin: add this to src/service-worker.js */
import { precacheAndRoute } from 'workbox-precaching'
import { Prefetcher } from '@xdn/prefetch/sw'

new Prefetcher().route()
/* end: add this to src/service-worker.js */

Then start the service:

xdn run

Open and observe the error in the dev console.