[9.5] optional catch all routes req.query.params behavior is different when deployed on vercel (works in dev, works in 9.4.4)

[vvo]

Bug report

Describe the bug

Hi, just tried to upgrade from 9.4.4 to 9.5.0. I was previously using the experimental optionalCatchAll flag. On 9.5.0 my optional catch-all routes are working in dev mode (next dev) but no more working when deployed on Vercel.

The issue is that req.query.params value is different between Vercel and dev mode when using optional catch-all routes.

To Reproduce

Steps to reproduce the behavior, please provide code snippets or a repository:

Given a project structure of:

- project
- api/
- api/organizations/
- api/organizations/[organizationId]
- api/organizations/[organizationId]/teams/
- api/organizations/[organizationId]/teams/[[...params]].js

When calling https://example.com/organizations/200/teams on vercel (9.5.0):

• req.query.params value: [""]

When calling https://localhost/organizations/200/teams on next dev (9.5.0):

• req.query.params value: undefined

When calling https://example.com/organizations/200/teams on vercel (9.4.4):

• req.query.params value: undefined

When calling https://localhost/organizations/200/teams on next dev (9.4.4):

• req.query.params value: undefined

Expected behavior

Both vercel and next dev should send the same value for req.query.params, maybe sticking to undefined or anything else that makes sense given current APIs.

System information

• OS: macOS
• Version of Next.js: 9.5.0
• Version of Node.js: 12.8.3

Additional context

n/a

[Janpot]

Does next build => next start behave the same way?

[NBruhno]

I have a similar issue. If I build it locally and run it with next start, the routes work, same with vercel dev. But deployed on Vercel, it fails with a 502 initially and continuos tries returns a 405 for me because the method is gone. Just to add, this used to work just fine in the last version while it was experimental for me as well, if that helps.

[stevez86]

I have a possibly related issue for a monorepo setup after upgrading to 9.5. I think it has to do with the routes in now.json not working correctly. I have this;

{
   ...
  "builds": [{ "src": "brand/next.config.js", "use": "@now/next" }],
  "routes": [{ "src": "/(.*)", "dest": "/brand/$1", "continue": true }]
}

Everything works in development, but on vercel my APIs fail and the homepage gets redirected to /brand. Please let me know what you need from me or if this should be a separate issue.