Improve Proxy invalid export error message

[devjiwonchoi]

Improve invalid Proxy/Middleware export error message to:

> Build error occurred
Error: The file "./proxy.ts" must export a function, either as a default export or as a named "proxy" export.
This function is what Next.js runs for every request handled by this proxy (previously called middleware).

Why this happens:
- You are migrating from `middleware` to `proxy`, but haven't updated the exported function.
- The file exists but doesn't export a function.
- The export is not a function (e.g., an object or constant).
- There's a syntax error preventing the export from being recognized.

To fix it:
- Ensure this file has either a default or "proxy" function export.

Learn more: https://nextjs.org/docs/messages/middleware-to-proxy

Turbopack:

Error: Turbopack build failed with 1 errors:
./proxy.ts
Proxy is missing expected function export name
This function is what Next.js runs for every request handled by this proxy (previously called middleware).

Why this happens:
- You are migrating from `middleware` to `proxy`, but haven't updated the exported function.
- The file exists but doesn't export a function.
- The export is not a function (e.g., an object or constant).
- There's a syntax error preventing the export from being recognized.

To fix it:
- Ensure this file has either a default or "proxy" function export.

Learn more: https://nextjs.org/docs/messages/middleware-to-proxy

Closes NEXT-4741

[devjiwonchoi]

• Only allow node runtime in proxy #85139
• Improve Proxy invalid export error message #84887 👈 (View in Graphite)
• fix: throw error during build when invalid export for Proxy #84886
• canary

This stack of pull requests is managed by Graphite. Learn more about stacking.

[devjiwonchoi]

Merge activity

• Oct 21, 8:54 PM UTC: @devjiwonchoi merged this pull request with Graphite.