Empty dynamic URL param

[Fanda36]

Describe the bug I created universal route routes/convert/[...format(.*)].svelte for handling every request (convert/*, including convert/). It works on dev server sapper dev --no-hot. When I go to localhost:3000/convert/ then I got result from [...format(.*)].svelte.

The problem is if I generate static web NODE_ENV=production sapper export, then mypage.com/convert/ return 404 not found.

To Reproduce

• do a file routes/convert/[...format(.*)].svelte
• create <a href="convert">test</a> in routes/index.svelte
• generate export NODE_ENV=production sapper export
• page myweb.com/convert/ return 404

Expected behavior Page myweb.com/convert/ will be rendered.

Information about your Sapper Installation:

• The output of npx envinfo --system --npmPackages svelte,sapper,rollup,webpack --binaries --browsers

  System:
  OS: Linux 5.9 Manjaro Linux
  CPU: (12) x64 AMD Ryzen 5 2600 Six-Core Processor
  Memory: 836.11 MB / 15.62 GB
  Container: Yes
  Shell: 5.1.0 - /bin/bash
  Binaries:
  Node: 14.15.4 - /usr/bin/node
  Yarn: 1.22.10 - /usr/bin/yarn
  npm: 6.14.11 - /usr/bin/npm
  Browsers:
  Firefox: 84.0.2
  npmPackages:
  sapper: ^0.28.0 => 0.28.10 
  svelte: ^3.17.3 => 3.31.2 
  webpack: ^4.7.0 => 4.46.0

• Your hosting environment - static

• If it is an exported (npm run export) or dynamic application - exported

Severity How severe an issue is this bug to you? Is this annoying, blocking some users, blocking an upgrade or blocking your usage of Sapper entirely?

• I have to have duplicity index.svelte and [...format(.*)].svelte has same content.

[peopledrivemecrazy]

Can you publish a repo?

[zimnicky]

Having the same requirements for our app:

• Routes like /category, /category/color_red, /category/color_red_yellow/size_m

We don't use static export, however, the described above trick with [...args(.*)] doesn't work with a dynamic app too and a workaround with index.svelte + [...args].svelte causing a lot of issues in the state management and transitions, so it would be great if this could be fixed.

I've created a repo with a modified starter template to demonstrate the issue: https://github.com/zimnicky/sapper-empty-route-test

Expected behavior: /hats shouldn't return 404