Verify canary release

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

Provide environment information

    Operating System:
      Platform: darwin
      Arch: arm64
      Version: Darwin Kernel Version 21.5.0: Tue Apr 26 21:08:37 PDT 2022; root:xnu-8020.121.3~4/RELEASE_ARM64_T6000
    Binaries:
      Node: 16.15.1
      npm: 8.11.0
      Yarn: 1.22.19
      pnpm: 7.3.0
    Relevant packages:
      next: 12.2.1-canary.1
      eslint-config-next: 12.2.0
      react: 18.2.0
      react-dom: 18.2.0

What browser are you using? (if relevant)

No response

How are you deploying your application? (if relevant)

No response

Describe the Bug

In 12.2, the middleware.ts file should be placed in the root directory next to the pages folder. However, when using the pageExtensions option in the next.config.js it is never being called.

Removing the setting allows you to call the middleware.

Renaming the middleware.ts file to middleware.api.ts in this case will make it work too. However, I don't believe the middleware is a "page" as it lives outside the pages folder.

Pre-12.2, it was called _middleware.ts and it did ignore the set page extensions.

Expected Behavior

The middleware should be called even when having set custom page extensions by ignoring those as it lives outside the /pages folder.

Or

The documentation should mention it is a "page" file and requires to have one of the set page extensions.

Link to reproduction

https://github.com/bjarn/next-middleware-bug

To Reproduce

Breaks when adding pageExtensions: ["api.ts", "page.tsx"], to the next.config.js. Removing fixes the issue.