Middleware in a [dynamic] route subdirectory runs against parent urls

Verify canary release

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

Provide environment information

    Operating System:
      Platform: darwin
      Arch: arm64
      Version: Darwin Kernel Version 21.4.0: Mon Feb 21 20:35:58 PST 2022; root:xnu-8020.101.4~2/RELEASE_ARM64_T6000
    Binaries:
      Node: 16.14.2
      npm: 8.5.0
      Yarn: 1.22.18
      pnpm: N/A
    Relevant packages:
      next: 12.1.0
      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

With a page structure like:

// pages/index.js
// pages/[customer]/_middleware.js
// pages/[customer]/dashboard.js

And a pages/[customer]/_middleware file containing:

export function middleware(req: NextRequest) {
  console.log(req.url)
}

I would expect _middleware to only apply to pages that resolve within that subdirectory, however it gets applied to every request:

wait  - compiling /[team]/_middleware...
event - compiled client and server successfully in 114 ms (765 modules)
http://localhost:3000/api/auth/session
http://localhost:3000/api/session
wait  - compiling /api/auth/[...nextauth]...
wait  - compiling /api/session...
event - compiled client and server successfully in 86 ms (779 modules)
http://localhost:3000/customer/1/dashboard
http://localhost:3000/_next/static/chunks/main.js?ts=1648344461416
http://localhost:3000/_next/static/chunks/webpack.js?ts=1648344461416
http://localhost:3000/_next/static/chunks/react-refresh.js?ts=1648344461416
http://localhost:3000/_next/static/chunks/pages/_app.js?ts=1648344461416
http://localhost:3000/_next/static/development/_buildManifest.js?ts=1648344461416
http://localhost:3000/_next/static/development/_ssgManifest.js?ts=1648344461416
http://localhost:3000/_next/static/chunks/pages/_error.js?ts=1648344461416
http://localhost:3000/_next/static/development/_middlewareManifest.js?ts=1648344461416
http://localhost:3000/api/session
http://localhost:3000/api/auth/session
http://localhost:3000/favicon.ico

Expected Behavior

I would expect the middleware not to be invoked on an unmatched route.

To Reproduce

See above description with a trivial example.

[balazsorban44]

The fix has been reverted as it seemed to break in certain cases. I’m reopening because this needs further investigation.

[balazsorban44]

This has recently been fixed in #32601. Please give canary a try!