How to find out which file NPX runs?

[Finesse]

When you run, say, npx webpack in a terminal, NPX finds a webpack package somewhere and runs it. How to identify the exact location of the binary that NXP runs? I'm looking for a tool like which in NPX.

Maybe there is an option like this (warning, it's not a real code):

$ npx --which webpack
Local file /users/me/my-project/node_modules/.bin/webpack

$ npx --which rollup
Remote package https://www.npmjs.com/package/rollup

If there is no such feature, I request it.

Just in case, I use Node.js v10.16.3, NPM v6.12.0, NPX v6.12.0.

[heyimalex]

This would be very helpful for create-react-app, where we occasionally get issues because people are running older versions. Telling them to run again with --ignore-existing works to make sure it's not an actual bug, but --which would let them know whether it's a global or local install they need to remove.

[karfau]

@Finesse I guess you are using NPX 10.12, not 6.12?

[Finesse]

@karfau No:

Finesse ~ % npx --version
6.13.4
Finesse ~ % npm --version
6.13.4
Finesse ~ % node --version
v10.16.3

[karfau]

It looks as if npx just reports the version of npm when asked for it's version:

$ node --version
v10.18.0
$ npm --version
6.13.4
$ npx --version
6.13.4

but I traced it down to the version of libnpx that is used:

$ cat /home/karfau/.nvm/versions/node/v10.18.0/lib/node_modules/npm/node_modules/libnpx/package.json 
{
  "_args": [
    [
      "libnpx@10.2.0",
      "/Users/rebecca/code/npm"
    ]
  ],
  "_from": "libnpx@10.2.0",
  "_id": "libnpx@10.2.0",
  "_inBundle": false,
  "_integrity": "sha512-X28coei8/XRCt15cYStbLBph+KGhFra4VQhRBPuH/HHMkC5dxM8v24RVgUsvODKCrUZ0eTgiTqJp6zbl0sskQQ==",
  "_location": "/libnpx",
  "_phantomChildren": {},
  "_requested": {
    "type": "version",
    "registry": true,
    "raw": "libnpx@10.2.0",
    "name": "libnpx",
    "escapedName": "libnpx",
    "rawSpec": "10.2.0",
    "saveSpec": null,
    "fetchSpec": "10.2.0"
  },
  "_requiredBy": [
    "/"
  ],
  "_resolved": "https://registry.npmjs.org/libnpx/-/libnpx-10.2.0.tgz",
  "_spec": "10.2.0",
  "_where": "/Users/rebecca/code/npm",
  "author": {
    "name": "Kat Marchán",
    "email": "kzm@sykosomatic.org"
  },
  "bugs": {
    "url": "https://github.com/zkat/npx/issues"
  },
  "config": {
    "nyc": {
      "exclude": [
        "node_modules/**",
        "test/**"
      ]
    }
  },
  "dependencies": {
    "dotenv": "^5.0.1",
    "npm-package-arg": "^6.0.0",
    "rimraf": "^2.6.2",
    "safe-buffer": "^5.1.0",
    "update-notifier": "^2.3.0",
    "which": "^1.3.0",
    "y18n": "^4.0.0",
    "yargs": "^11.0.0"
  },
  "description": "support library for npx -- an tool for executing npm-based packages.",
  "devDependencies": {
    "cross-env": "^5.1.3",
    "json": "^9.0.6",
    "marked-man": "^0.2.1",
    "mkdirp": "^0.5.1",
    "npm": "^5.7.1",
    "nyc": "^11.4.1",
    "require-inject": "^1.4.0",
    "standard": "^11.0.0",
    "standard-version": "^4.3.0",
    "tacks": "^1.2.6",
    "tap": "^11.1.2",
    "weallbehave": "^1.2.0",
    "weallcontribute": "^1.0.8"
  },
  "engines": {
    "node": ">=4"
  },
  "files": [
    "*.js",
    "libnpx.1",
    "locales"
  ],
  "homepage": "https://github.com/zkat/npx#readme",
  "keywords": [
    "npm",
    "npm exec",
    "shell",
    "scripts",
    "npm bin",
    "cli"
  ],
  "license": "ISC",
  "main": "index.js",
  "man": [
    "./libnpx.1"
  ],
  "name": "libnpx",
  "repository": {
    "type": "git",
    "url": "git+https://github.com/zkat/npx.git"
  },
  "scripts": {
    "bin": "make bin",
    "docs": "tail -n +2 README.md | marked-man --manual 'User Commands' --version \"$npm_package_name@$npm_package_version\" > $npm_package_name.1",
    "postrelease": "npm publish && git push --follow-tags",
    "prerelease": "npm t && npm run docs",
    "pretest": "standard *.js test bin/*.js locales",
    "publish-bin": "npm run bin && cd bin && npm publish",
    "release": "standard-version -s",
    "test": "cross-env NPX_UPDATE_LOCALE_FILES=true LC_ALL=en nyc --all -- tap -J test/*.js",
    "update-coc": "weallbehave -o . && git add CODE_OF_CONDUCT.md && git commit -m 'docs(coc): updated CODE_OF_CONDUCT.md'",
    "update-contrib": "weallcontribute -o . && git add CONTRIBUTING.md && git commit -m 'docs(contributing): updated CONTRIBUTING.md'"
  },
  "version": "10.2.0"
}

So I guess there is another issue to report regarding the --version behavior...

[Finesse]

Looks like the following command works:

# Replace `webpack` with any package name
npx which webpack

It considers PATH and node_modules in parent directories. It can be the proper solution because NPX uses which as a dependency but the code is too tangled to find out whether it's 100% correct.