Unable to parse config export in source file

[r34son]

Link to the code that reproduces this issue

https://codesandbox.io/p/devbox/wonderful-haibt-mw8z7p

To Reproduce

export matcher config from middleware like this:

export const config = {
  matcher: [
    /*
     * Match all request paths except for the ones starting with:
     * - api (API routes)
     * - monitoring (sentry tunnel route)
     * - _next/static (static files)
     * - _next/image (image optimization files)
     * - favicon.ico (favicon file)
     * - sitemap.xml (sitemap file)
     * - robots.txt (robots file)
     * - manifest.webmanifest (manifest file)
     * - icon (icons)
     */
    {
      source:
        '/((?!api|monitoring|_next/static|_next/image|favicon.ico|sitemap.xml|robots.txt|manifest|icon).*)',
      missing: [
        { type: 'header', key: 'next-router-prefetch' },
        { type: 'header', key: 'purpose', value: 'prefetch' },
      ],
    },
  ],
};

Current vs. Expected behavior

next dev --turbo throws warnings:

 ⚠ ./src/middleware.ts
Unable to parse config export in source file
The exported configuration object in a source file need to have a very specific format from which some properties can be statically parsed at compiled-time.

Provide environment information

Operating System:
  Platform: darwin
  Arch: arm64
  Version: Darwin Kernel Version 23.3.0: Wed Dec 20 21:30:44 PST 2023; root:xnu-10002.81.5~7/RELEASE_ARM64_T6000
  Available memory (MB): 32768
  Available CPU cores: 10
Binaries:
  Node: 20.12.0
  npm: 10.5.0
  Yarn: N/A
  pnpm: 8.15.5
Relevant Packages:
  next: 14.2.0-canary.49 // Latest available version is detected (14.2.0-canary.49).
  eslint-config-next: 14.1.4
  react: 18.2.0
  react-dom: 18.2.0
  typescript: 5.4.3
Next.js Config:
  output: standalone

Which area(s) are affected? (Select all that apply)

Middleware / Edge (API routes, runtime), Turbopack (--turbo)

Which stage(s) are affected? (Select all that apply)

next dev (local)

Additional context

No response

_PACK-2899

[kamalciirs]

Can you please check the issue reproduce example link is unavailable.

[r34son]

Can you please check the issue reproduce example link is unavailable.

Updated link

[balazsorban44]

It looks like the parsing is incomplete at:

next.js/packages/next-swc/crates/next-core/src/util.rs

Lines 375 to 387 in 6a1e70a

	JsValue::Array { items, .. } => {
	for item in items {
	if let Some(matcher) = item.as_str() {
	matchers.push(matcher.to_string());
	} else {
	invalid_config(
	"The matcher property must be a string or array \
	of strings",
	value,
	);
	}
	}
	}

🤔 It should also allow objects as an item of the matchers array.

[Gawdfrey]

I bumped into this issue after upgrading to v14.2 just now. I have almost the exact same config as OP.
I guess this makes it so that the matcher is not respected and it applies to all routes? 🤔

[ivandamyanov]

I get the same issue when turning on --turbo with nextjs 14.2.1 with this matcher:

[
    {
      source: '/((?!api|_next/static|_next/image|__nextjs|.*\\..*|favicon.ico|auth/).*)',
      missing: [
        { type: 'header', key: 'next-router-prefetch' },
        { type: 'header', key: 'purpose', value: 'prefetch' },
      ],
    },
]

[biohackerellie]

+1, have the exact same issue, exact same config

export const config = {
  matcher: [
    {
      source: "/((?!api|_next/static|_next/image|favicon.ico).*)",
      missing: [
        { type: "header", key: "next-router-prefetch" },
        { type: "header", key: "purpose", value: "prefetch" },
      ],
    },
  ],
};

Unable to parse config export in source file 
The exported configuration object in a source file need to have a very specific format from which some properties can be statically parsed at compiled-time.

[jenewland1999]

+1, have the exact same issue with same config too. Seems to be a 14.2 specific thing.

[mwawrusch]

export const config = {
  matcher: [
    /*
     * Match all request paths except for the ones starting with:
     * - api (API routes)
     * - _next/static (static files)
     * - _next/image (image optimization files)
     * - favicon.ico (favicon file)
     */
    {
      source: '/((?!api|_next/static|_next/image|favicon.ico).*)',
      missing: [
        { type: 'header', key: 'next-router-prefetch' },
        { type: 'header', key: 'purpose', value: 'prefetch' },
      ],
    },
  ],
}

14.2.1

[timneutkens]

We've opened a fix here: #64678

[mwawrusch]

As always you guys rock. Thank you

[jenewland1999]

Thanks @timneutkens and team! Appreciate the fix!

[github-actions]

This closed issue has been automatically locked because it had no new activity for 2 weeks. If you are running into a similar issue, please create a new issue with the steps to reproduce. Thank you.