Rewrites bug when using with basePath and public directory

[giwan-dev]

Bug report

Describe the bug

Next.js cannot rewrites URL when using basePath option and having public directory.

To Reproduce

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

1. Clone the reproduction repo
2. Install dependencies, build next server, and run it.

npm install
npm run build
npm run start

3. GET the url what should be rewritten.

curl 'http://localhost:3000/todos'

4. See error

Expected behavior

$ curl 'http://localhost:3000/todos'
HTTP/1.1 200 OK
...

System information

• OS: macOS
• Version of Next.js: 9.5.2
• Version of Node.js: v12.18.0

Additional context

Add any other context about the problem here.

[inbeom]

Next.js dev server behaves as expected. After running npm run dev:

$ curl -I http://localhost:3000/todos
HTTP/1.1 200 OK
date: Wed, 19 Aug 2020 02:56:51 GMT
content-type: application/json; charset=utf-8
connection: close
...

It fails only if the server is running in non-development mode.

[inbeom]

After some investigation, I found the current matching order of Routes always puts public routes which is in fsRoutes before rewrite routes if ./public directory is present.

From this if branch for early routing failure added from #15041 lets next-server to respond with 404 to every request not having basePath as its path prefix for public routes. It assumes all of the non-custom routes with lower precedence than the fs route requires basePath to be present, while for rewrite routes it might not be true.

Although I am not fully aware of the context of this decision, but I suppose the assumption of public routes and the early routing failure conflicts with each other. We might:

• continue regardless of requireBasePath: This runs fine on my environment. But I think there might be problems regarding the final catchAllRoute, which would create false positive matches. (Or not? 😵)
• Pass publicRoutes and the rest of fsRoutes separately down to Router, and put publicRoutes after rewrites: It seems to be a safer choice, but it does not fully reflect the priority of routes order introduced from Update next-server routes order for expected priority #10326

Which direction should we take further?

[inbeom]

Opened a PR with the first solution. Hope this helps. Thanks!

[balazsorban44]

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