Tricks for debugging Vercel builds

Rapid fire, here are some of the things that I've run into while doing builds on Vercel or just with Next.JS that might help you out.

Issue #1: ERR_PNPM_EXDEV

If you see something like this:

ERR_PNPM_EXDEV EXDEV: cross-device link not permitted, copyfile '/vercel/path0/node_modules/.pnpm-store/v10/files/0a/ae75830ac8025d8069cc23f4732111e5f9cd2472b8afa49658fe912583400d01c204ee01b4bad2ec3ee7c578e2106cf44d01fd263ea22b4a33a080bf0b9e05-exec' -> '/vercel/path0/node_modules/.pnpm/@esbuild+linux-x64@0.20.2/node_modules/@esbuild/linux-x64_tmp_70/bin/esbuild'
Error: Command "pnpm install" exited with 1

You should try creating a file called .npmrc in your project root with this content:

node-linker=isolated
shamefully-hoist=true

If you're a pnpm master you're probably thinking... isn't isolated the default? I think it's supposed to be, but I think the Vercel build process may change it to something else. The shamefully hoist option is something that I've seen recommended specifically for Vercel in other places.

Issue #2: TypeError: tT is not a constructor or similar

If you see something like this:

TypeError: tT is not a constructor

It will probably recommend you look into these pre-render error suggestions.

If that doesn't help then you should try looking for circular dependencies. Running pnpx madge --circular --extensions ts ./ in the root of your project will help you find them.

The compiler doesn't always like circular dependencies so this can blow things up in a strange way.