Upgraded to Next 14. Build fails in build trace

[JoaoCnh]

Summary

I have an application that was working fine in Next 12.
By itself the application doesn't use almost any Next features, the most I use is the _app, _document and _error files. I also have a custom express server. I guess what I'm trying to say is that is not awfully complex, it's a pretty straightforward app.

As soon as I upgrade to either Next 13 or Next 14 the application fails in the build trace with this error:

TypeError: Cannot convert a Symbol value to a string
    at Object.TemplateLiteral (/Users/myuser/project/node_modules/next/dist/compiled/@vercel/nft/index.js:1:68872)
    at async Object.BinaryExpression (/Users/myuser/project/node_modules/next/dist/compiled/@vercel/nft/index.js:1:60629)
    at async Object.ArrayExpression (/Users/myuser/project/node_modules/next/dist/compiled/@vercel/nft/index.js:1:60189)
    at async computePureStaticValue (/Users/myuser/project/node_modules/next/dist/compiled/@vercel/nft/index.js:1:21303)
    at async Object.enter (/Users/myuser/project/node_modules/next/dist/compiled/@vercel/nft/index.js:1:27826)
    at async AsyncWalker.visit (/Users/myuser/project/node_modules/next/dist/compiled/@vercel/nft/index.js:24:15230)
    at async AsyncWalker.visit (/Users/myuser/project/node_modules/next/dist/compiled/@vercel/nft/index.js:24:15688)
    at async AsyncWalker.visit (/Users/myuser/project/node_modules/next/dist/compiled/@vercel/nft/index.js:24:15769)
    at async AsyncWalker.visit (/Users/myuser/project/node_modules/next/dist/compiled/@vercel/nft/index.js:24:15769)
    at async AsyncWalker.visit (/Users/myuser/project/node_modules/next/dist/compiled/@vercel/nft/index.js:24:15688)

I've been trying for ages to try and figure out what is the cause and what I have to do but I can't seem to debug what the file tracing is doing.

Does anyone have any pointers?

Additional information

No response

Example

No response

[icyJoseph]

nft walks your project, to figure out what has to be included for an application to work.

What could be happening here is that a string concatenation is happening.

I wonder if you could turn off SWC minification? There's a next.config.js flag, called swcMinify, set that to false and try again.

I take it that, you don't really use Symbols, right?

[JoaoCnh]

I tried it anyway and it seems to fail with the same error

[icyJoseph]

It should be there, it was only removed recently, in v15.

[icyJoseph]

I'd say then, good ol' remove stuff until it works... and go from there

[JoaoCnh]

Yeah I started doing that as my last effort and I started noticing a pattern. Every file that had newrelic imported in it would cause the build trace to fail. I noticed I had an out of date newrelic agent version and after the upgrade it worked without issues.
Still don't know what was causing the issue but happy I got it working!