unexpected token export in generated client.js after upgrading to 0.29.0

[danphil]

Describe the bug Upon upgrading to 0.29.0, a previously working dynamic app results in "Unexpected token: export..." in Chrome-stable-latest and "export must be at the top..." in FF-stable-latest in the sapper generated client.js chunk. First page renders correctly but has no functionality.

Logs Uncaught SyntaxError: export declarations may only appear at top level of a module client.33c71ccb.js:2224

To Reproduce 1) Clone sapper-template 2) Upgrade sapper to 0.29.0 in package.json 3) npm install, npm run dev 4) Open localhost:3000

Expected behavior Upgrade, change rel=prefetch to sapper:prefetch, ???, profit

Information about your Sapper Installation:

• System: OS: Linux 4.18 CentOS Linux 8 CPU: (4) x64 Intel(R) Xeon(R) CPU X3430 @ 2.40GHz Memory: 380.96 MB / 1.82 GB Container: Yes Shell: 4.4.19 - /bin/bash
  • Binaries: Node: 14.15.4 - ~/.nvm/versions/node/v14.15.4/bin/node npm: 6.14.11 - ~/.nvm/versions/node/v14.15.4/bin/npm
  • Packages: see sapper template
  • Browser: Firefox 84.0.2
  • Hosting environment: local, nginx

Severity Blocking upgrade.