Rollup variant of the sapper template is broken since @rollup/[email protected] was released

[bryanwood]

A fresh degit of the template since @rollup/[email protected] was released results in the following:

C:\projects>npx degit sveltejs/sapper-template#rollup my-app
>> cd my-app
>> npm install
>> npm run dev
npx: installed 1 in 1.297s
> cloned sveltejs/sapper-template#rollup to my-app
npm notice created a lockfile as package-lock.json. You should commit this file.
npm WARN [email protected] No repository field.
npm WARN [email protected] No license field.

added 271 packages from 199 contributors and audited 2224 packages in 6.095s

19 packages are looking for funding
  run `npm fund` for details

found 1 moderate severity vulnerability
  run `npm audit fix` to fix them, or `npm audit` for details

> [email protected] dev C:\projects\my-app
> sapper dev

✗ client
'import' and 'export' may only appear at the top level
11: }
12:
13: export function connect(port) {
    ^
14:   if (source || !window.EventSource) return;
✔ server (806ms)
✔ service worker (189ms)
> Listening on http://localhost:3001

Pinning @rollup/plugin-commonjs to 11.0.2 resolves it.

Possibly relevant commits from @rollup/plugin-commonjs:

• rollup/plugins@04138d6
• rollup/plugins@cbc341d
• rollup/plugins@a66c8c7
• rollup/plugins@b662126
• rollup/plugins@4207609

[Conduitry]

Closing in favor of sveltejs/sapper#1151 which has more discussion, but it does seem like this is probably something that needs to be fixed in the Rollup plugin.