import "yargs/yargs" in esm code brings in __dirname (when compiled using ncc)

[chubei-urus]

Reproduce

node --version
v20.11.1

Create package.json and index.mjs with following code:

{
  "scripts": {
    "build": "ncc build index.mjs"
  },
  "dependencies": {
    "yargs": "^17.7.2"
  },
  "devDependencies": {
    "@vercel/ncc": "^0.38.1"
  }
}

import yargs from "yargs/yargs";
console.log(yargs);

Run command:

npm install
npm run build
node dist/index.mjs

Exepcted

[Function (anonymous)] {
  applyExtends: [Function (anonymous)],
  hideBin: [Function: hideBin],
  Parser: [Function: Parser] {
    detailed: [Function (anonymous)],
    camelCase: [Function: camelCase],
    decamelize: [Function: decamelize],
    looksLikeNumber: [Function: looksLikeNumber]
  }
}

Actual

...
ReferenceError: __dirname is not defined in ES module scope
...

I think this has something to do with yargs.mjs importing build/index.cjs, but have no clue on how to solve it.

[shadowspawn]

I was able to reproduce the failure. My guess is ncc is getting confused resolving subpath exports.

I got a working build using the main entry point:

import yargsFactory from "yargs";
console.log(yargsFactory(process.argv.slice(2)).parse());

[chubei-urus]

Thank you for verifying this!

I feel ncc resolves the subpath export correctly, because the root cause seems to be that build/index.cjs uses the cjs shim, instead of the esm one. And the cjs shim uses __dirname, as it should be.

I ran into this because puppeteer imports yargs using "yargs/yargs". I see several solutions to this:

• Ask for yargs' help to fix yarngs.mjs to be fully esm compatible.
• Ask for puppeteer's help to change from importing "yargs/yargs" to "yargs".
• Change the module system in my own project to use commonjs instead of esm.

What's you recommended next step for this?

[shadowspawn]

What's you recommended next step for this?

I suggest try changing your project to use commonjs. That might avoid triggering the problem with the ncc compile.

[chubei-urus]

Got it. I'll leave the issue open in case someone else ran into this.