When middleware.ts is specified, runtime is set to edge instead of node

[ecumene]

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 22.3.0: Mon Jan 30 20:39:35 PST 2023; root:xnu-8792.81.3~2/RELEASE_ARM64_T8103
    Binaries:
      Node: 19.8.1
      npm: 9.5.1
      Yarn: 1.22.19
      pnpm: N/A
    Relevant packages:
      next: 13.3.1-canary.16
      eslint-config-next: 13.3.0
      react: 18.2.0
      react-dom: 18.2.0

Which area(s) of Next.js are affected? (leave empty if unsure)

Middleware / Edge (API routes, runtime)

Link to the code that reproduces this issue

https://github.com/ecumene/next-reproduce-edge-middleware

To Reproduce

1. Setup a next app and yarn build
2. Notice the .next project is built for a node runtime (Compatible with SST in my case)
3. Create a middleware.ts file
4. Notice the .next project is built for an edge runtime (Incompatible with SST)

Describe the Bug

An edge-runtime-webpack.js file is present in .next when it shouldn't be there.

Expected Behavior

The project should be built for a node runtime.

Which browser are you using? (if relevant)

No response

How are you deploying your application? (if relevant)

SST

[Defrosted]

The issues people have in #48302 are probably caused by this as well, as the libraries people use in their middlewares that have the same problem differ.

It's worth mentioning that a part of the issue here is also that the edge-chunks generated by the middleware during a standalone mode build aren't copied over to the standalone directory, causing the server function to outright crash when it attempts to load missing files.

[DuCanhGH]

@Defrosted

It's worth mentioning that a part of the issue here is also that the edge-chunks generated by the middleware during a standalone mode build aren't copied over to the standalone directory, causing the server function to outright crash when it attempts to load missing files.

I thought I fixed this a few months ago, perhaps something went wrong... Time to check :)

Edit: this is weird, seems that this no longer works... I'm on it :)

Edit 2: ah, it was never fixed for middleware...

[DuCanhGH]

@ecumene middleware.js only supports the Edge runtime (the maintainers wanted to make it lightweight as it is invoked every time a page is visited - even client-side transitions count). So perhaps this is working as intended, though you might want to make a feature request on that :)

[wowczarczyk]

@DuCanhGH is this related to: #48723 ?

[DuCanhGH]

@wowczarczyk no, but it is related to Defrosted's comment.

[wowczarczyk]

OK, cool, for now I added additional COPY statement in my Dockerfile to mitigate this:

COPY --from=builder --chown=nextjs:nodejs /app/.next/server/edge-chunks ./.next/server/edge-chunks