Yet another 126 error but only when testing with jest

[mathiasbockwoldt]

Not sure if this belongs here or rather in the jest issue tracker.

I wrote a package that uses native .dll/.so files. The including code looks like this:

import * as ffi from 'ffi-napi';
import * as ref from 'ref-napi';
import path from 'node:path';

const pathToDll ='./lib/win/mylib.dll';
const pathToSo = './lib/linux/mylib.so';
const pathToLib = process.platform === 'win32' ? pathToDll : pathToSo;

if (process.platform === 'win32') {
  const kernel32 = ffi.Library('kernel32', {
    SetDllDirectoryA: [ref.types.bool, [ref.types.CString]],
  });
  const dllDir = path.dirname(path.resolve(pathToDll));
  kernel32.SetDllDirectoryA(dllDir);
  const libPath = path.resolve('.');                                   // MARK
  process.env.PATH = `${process.env.PATH}${path.delimiter}${libPath}`; // MARK
}

export const mylib = ffi.Library(pathToLib, {
  testMethod: [ref.types.int, [ref.types.int]]
}

Under Linux, it works nicely. Under Windows it works if called directly from node or in a script, but if I call this using jest, I get Dynamic Linking Error: Win32 error 126.

There are two things here that puzzle me.

1. Why do I have to include the root path to the PATH env variable (lines marked with MARK)? If I delete these lines, the Windows version will create the 126 error also when calling the script directly. I don't understand this, because the dlls are in the ./lib/win directory and that is included via SetDllDirectory anyway.
2. The jest version works if I add the root folder of the script to PATH manually before I start jest. Either way (manually or by the lines marked with MARK), I can see that the root folder is in the PATH (via console.log), but it only works if I add it manually before starting jest.

[mathiasbockwoldt]

Related: jestjs/jest#13730

[mathiasbockwoldt]

Sorry, folks, my error.
The problem was not the path variable, but the relative path to the dll (const pathToDll ='./lib/win/mylib.dll';). That needs to become an absolute path.