Route under multiple optional parameters is not matched correctly in every case

[popapaul]

Describe the bug

In case of the following route structure:

• /[[culture=culture]]/[[year=year]]/program // Program route
• /[[culture=culture]]/[[year=year]]/[...content] // Content route

The following links will go correctly to Program route:

• /program ✓
• /en/program ✓
• /en/2022/program ✓

But /2022/program ✘ will instead go to Content route, practically turning the optional parameter culture into a required parameter when year is set which is not in my opinion the expected behaviour

1. Content route as rest parameter:

   Expected behaviour:

• /2022/program -> Program route

Actual behaviour:

• /2022/program -> Content route

Additionally

When changing /[[culture=culture]]/[[year=year]]/[...content] to /[[culture=culture]]/[[year=year]]/[content],

The following links will go correctly to Content route:

• /content ✓
• /en/content ✓
• /en/2022/content ✓

But

• /2022/content ✘
• /2022/program ✘

will both be met by 404 Not Found.

2. Content route as parameter:

Expected behaviour:

/2022/program -> Program route /2022/content -> Content route

Actual behaviour:

/2022/program -> 404 /2022/content -> 404

Reproduction

Stackblitz Reproduction

Logs

No response

System Info

System:
    OS: Windows 10 10.0.22621
    CPU: (12) x64 AMD Ryzen 5 3600 6-Core Processor
    Memory: 17.48 GB / 31.93 GB
  Binaries:
    Node: 18.16.0 - C:\Program Files\nodejs\node.EXE
    npm: 9.5.1 - C:\Program Files\nodejs\npm.CMD
    pnpm: 8.6.0 - C:\Program Files\nodejs\pnpm.CMD
  Browsers:
    Edge: Spartan (44.22621.2134.0), Chromium (116.0.1938.76)
    Internet Explorer: 11.0.22621.1
  npmPackages:
    svelte: ^4.2.0 => 4.2.0

Severity

serious, but I can work around it

Additional Information

No response

[allozaur]

I've also encountered this issue in my project that's using "@sveltejs/kit": "^2.0.0"" and "svelte": "^4.2.7"".

[!NOTE] This issue only persists if the Level 1 route (lang param) is optional. If it's a required level route, then the problem goes away. Alternatively it also works when lang route is optional, but when instead of [explore=explore] we use hardcoded value for this route level.

Not working

My structure looks like this:

• [[lang=lang]]/
  • [explore=explore]/ +page.server.js
  • [offer_type=offer_type]/
    • [[city=city]]/
    • [[district=district]]/
      • [[subdistrict=subdistrict]]/ +page.server.js
      • [view_mode=view_mode]/ +page.svelte

Routes that are working:

• /en/explore/sale/map — here city, district and subdistrict params are not present
• /en/explore/sale/warszawa/srodmiescie/powisle/map — here all 3 optional parameters are present

Routes that are returning 404:

• /en/explore/sale/warszawa/map — here we are missing district and subdistrict optional params
• /en/explore/sale/warszawa/srodmiescie/map — here we are just missing subdistrict optional param

Working

• [lang=lang]/

  • [explore=explore]/ +page.server.js
  • [offer_type=offer_type]/
    • [[city=city]]/
    • [[district=district]]/
      • [[subdistrict=subdistrict]]/ +page.server.js
      • [view_mode=view_mode]/ +page.svelte

• [[lang=lang]]/

  • explore/ +page.server.js
  • [offer_type=offer_type]/
    • [[city=city]]/
    • [[district=district]]/
      • [[subdistrict=subdistrict]]/ +page.server.js
      • [view_mode=view_mode]/ +page.svelte