Regression in "require" in ES6 modules. Fails to find "ws" module.

[RamiHg]

It looks like a recent change to revert a commit that removed uses of require didn't quite fully revert to the old behavior.

I was getting a bizarre error where Node would refuse to find the "ws" module even though I had installed it using npm install ws. I build my code using -sMODULARIZE -sEXPORT_ES6. The error was:

Error: Cannot find module 'ws'
Require stack:
- /noop.js
    at Module._resolveFilename (node:internal/modules/cjs/loader:1060:15)
    at Module._load (node:internal/modules/cjs/loader:905:27)
    at Module.require (node:internal/modules/cjs/loader:1127:19)
    at require (node:internal/modules/helpers:112:18)

"ws" was getting imported from libsockfs.js in the listen function:

        var WebSocketServer = require('ws').Server;
        var host = sock.saddr;

The original code that was initially reverted called createRequire like this:

  const { createRequire } = await import('module');
  let dirname = import.meta.url;
  if (dirname.startsWith("data:")) {
    dirname = '/';
  }
  /** @suppress{duplicate} */
  var require = createRequire(dirname);

However, the change that re-introduced the old code instead introduced it as:

  const { createRequire } = await import('module');
  /** @suppress{duplicate} */
  var require = createRequire('/');

I'm not very familiar with Javascript and Node, but after much head-scratching, I tracked it down to that piece of code. If I replace the createRequire with the original version (the one that first checks for "data:"), my code works!

I can create a simple PR to do that fix if needed.

Thanks!

[sbc100]

Interesting. I assumed that the parameter to createRequire was only needed for relative imports like ./foo not for system imports like ws. I guess I was wrong. I guess we need some more testing here.

[sbc100]

Just to confirm, are you trying to actually build websocket server using emscripten that runs in node? Or is this code just getting included incidentally somehow?

[RamiHg]

Thanks for the quick reply! And yes. I am building a websocket server using emscripten. (Well, I'm porting a POSIX socket server).

[sbc100]

The fix seems easier enough, although I'm having trouble being able to test this (because out test code sets NODE_PATH=..., which obviates the need for the fix).

Can you say more about your use case. Are you running your emscripten-generate code both in node and in the browser?