Custom server: app.render() not recognizing passed query params correctly

[jackyef]

Verify canary release

• I verified that the issue exists in the latest Next.js canary release

Provide environment information

Operating System:
Platform: linux
Arch: x64
Version: #1 SMP Fri Apr 2 22:23:49 UTC 2021
Binaries:
Node: 16.16.0
npm: 8.11.0
Yarn: 1.22.19
pnpm: 7.7.0
Relevant packages:
next: 12.3.2-canary.10
eslint-config-next: 12.3.0
react: 17.0.2
react-dom: 17.0.2

What browser are you using? (if relevant)

No response

How are you deploying your application? (if relevant)

No response

Describe the Bug

Since 12.1.0, passed query params to app.render() in a custom server implementation aren't getting recognized correctly.

Consider the following custom express server:

server.get('/:id', async (req, res) => {  
  return app.render(req, res, '/[id]', {id: req.params.id}, `/${req.params.id}`)
})

Given ./pages/[id] exists, in 12.0.10, when visiting /page/123, ctx.router.query.id in getInitialProps and useRouter().query.id in components will return 123.

This however is not the case since 12.1.0. The value would be the literal string "[id]" instead. This issue still happens in latest canary release.

---

FWIW, I can achieve the same thing in >= 12.1.0 by updating the line to the following. Though with that being said, I am not sure if the behavior change is expected, especially since app.render() does accept a query object.

server.get('/:id', async (req, res) => {  
  return app.render(req, res, `/${req.params.id}`)
})

After doing some digging, it seems like the params returned by dynamicRoute.match() is { '[id]': '[id]' } instead of { '[id]': '123' }, which could be the problem.

This commit (a1b8a96) seems to be the one that introduced the behavior difference.

Expected Behavior

The 12.0.10 behavior should persists.

When visiting /page/123, ctx.router.query.id in getInitialProps and useRouter().query.id in components should return 123.

Link to reproduction

https://github.com/jackyef/next-1210-custom-server

To Reproduce

Clone the following repo.

1. Install next 12.0.10, run next dev and visit /123
2. Install next 12.1.0, run next dev and visit /123
3. See the difference of the router.query.id value

[Enrique-Ambrocio]

Hi there! Is there any way I can help? I'm actually looking to contribute to my first open-source project.

[thiefjim]

same issue here #41383