Laravel mix always undefined in mix v4+ - laravel

Question

Any call to npm run after upgrading to Mix v4.x results in mix being undefined. I see errors like this on every run:
> npm run development
> # development /project
> cross-env NODE_ENV=development node_modules/webpack/bin/webpack.js --progress --hide-modules --config=node_modules/laravel-mix/setup/webpack.config.js
/project/node_modules/webpack-cli/bin/cli.js:235
throw err;
^
TypeError: Cannot read property 'js' of undefined
at Object.<anonymous> (/project/webpack.mix.js:15:5)
at Module._compile (/project/node_modules/v8-compile-cache/v8-compile-cache.js:178:30)
at Object.Module._extensions..js (internal/modules/cjs/loader.js:732:10)
at Module.load (internal/modules/cjs/loader.js:620:32)
at tryModuleLoad (internal/modules/cjs/loader.js:560:12)
at Function.Module._load (internal/modules/cjs/loader.js:552:3)
at Module.require (internal/modules/cjs/loader.js:657:17)
at require (/project/node_modules/v8-compile-cache/v8-compile-cache.js:159:20)
at Object.<anonymous> (/project/node_modules/laravel-mix/setup/webpack.config.js:12:1)
at Module._compile (/project/node_modules/v8-compile-cache/v8-compile-cache.js:178:30)
at Object.Module._extensions..js (internal/modules/cjs/loader.js:732:10)
at Module.load (internal/modules/cjs/loader.js:620:32)
at tryModuleLoad (internal/modules/cjs/loader.js:560:12)
at Function.Module._load (internal/modules/cjs/loader.js:552:3)
at Module.require (internal/modules/cjs/loader.js:657:17)
at require (/project/node_modules/v8-compile-cache/v8-compile-cache.js:159:20)
at WEBPACK_OPTIONS (/project/node_modules/webpack-cli/bin/convert-argv.js:113:13)
at requireConfig (/project/node_modules/webpack-cli/bin/convert-argv.js:115:6)
at /project/node_modules/webpack-cli/bin/convert-argv.js:122:17
at Array.forEach (<anonymous>)
at module.exports (/project/node_modules/webpack-cli/bin/convert-argv.js:120:15)
at yargs.parse (/project/node_modules/webpack-cli/bin/cli.js:232:39)
at Object.parse (/project/node_modules/yargs/yargs.js:567:18)
at /project/node_modules/webpack-cli/bin/cli.js:210:8
at Object.<anonymous> (/project/node_modules/webpack-cli/bin/cli.js:500:3)
at Module._compile (internal/modules/cjs/loader.js:721:30)
at Object.Module._extensions..js (internal/modules/cjs/loader.js:732:10)
at Module.load (internal/modules/cjs/loader.js:620:32)
at tryModuleLoad (internal/modules/cjs/loader.js:560:12)
at Function.Module._load (internal/modules/cjs/loader.js:552:3)
at Module.require (internal/modules/cjs/loader.js:657:17)
at require (internal/modules/cjs/helpers.js:22:18)
at Object.<anonymous> (/project/node_modules/webpack/bin/webpack.js:155:2)
at Module._compile (internal/modules/cjs/loader.js:721:30)
at Object.Module._extensions..js (internal/modules/cjs/loader.js:732:10)
at Module.load (internal/modules/cjs/loader.js:620:32)
npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! # development: `cross-env NODE_ENV=development node_modules/webpack/bin/webpack.js --progress --hide-modules --config=node_modules/laravel-mix/setup/webpack.config.js`
npm ERR! Exit status 1
npm ERR!
npm ERR! Failed at the # development script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.
I'm running this with Laravel 5.5. I upgraded package.json to match the version in the laravel repo that is used with mix v4.
Here is my package.json:
{
"private": true,
"scripts": {
"dev": "npm run development",
"development": "cross-env NODE_ENV=development node_modules/webpack/bin/webpack.js --progress --hide-modules --config=node_modules/laravel-mix/setup/webpack.config.js",
"watch": "npm run development -- --watch",
"watch-poll": "npm run watch -- --watch-poll",
"hot": "cross-env NODE_ENV=development node_modules/webpack-dev-server/bin/webpack-dev-server.js --inline --hot --config=node_modules/laravel-mix/setup/webpack.config.js",
"prod": "npm run production",
"production": "cross-env NODE_ENV=production node_modules/webpack/bin/webpack.js --no-progress --hide-modules --config=node_modules/laravel-mix/setup/webpack.config.js"
},
"devDependencies": {
"accounting": "^0.4.1",
"axios": "^0.18.0",
"bootstrap": "^4.1.3",
"bootstrap-sass": "^3.4.0",
"cross-env": "^5.2.0",
"fancybox": "^3.0.1",
"jquery": "^3.3.1",
"jquery-slimscroll": "^1.3.8",
"ladda": "^2.0.1",
"laravel-mix": "^4.0.13",
"locutus": "^2.0.10",
"metismenu": "^2.7.9",
"moment": "^2.23.0",
"vue": "^2.5.21",
"webpack": "^4.28.3",
"webpack-cli": "^3.2.0"
},
"dependencies": {
"ajv": "^6.6.2",
"bootstrap-vue": "^2.0.0-rc.11",
"extract-text-webpack-plugin": "^4.0.0-beta.0",
"imagemin": "^6.0.0",
"jsonexport": "^2.4.1",
"laravel-echo": "^1.5.2",
"lodash": "^4.17.11",
"node-sass": "^4.11.0",
"pusher-js": "^4.3.1",
"sweetalert2": "^7.32.4",
"vue-api-query": "^1.2.0",
"vue-events": "^3.1.0",
"vue-multiselect": "^2.1.3",
"vue-sweetalert2": "^1.6.3",
"vuetable-2": "^2.0.0-beta.4",
"vuex": "^3.0.1"
}
}
My webpack.mix.js:
const { mix } = require('laravel-mix');
mix.js('resources/assets/js/app.js', 'public/js')
.sass('resources/assets/sass/app.scss', 'public/css')
.version()
.sourceMaps();
I've tried deleting node_modules and yarn install again but that doesn't fix it.
If I downgrade to v3, there are no issues other than problems compiling some SASS.
npm v6.4.1
node v11.5.0
yarn v1.12.3

Answer 1

Without seeing your webpack.mix.js file it's hard to say what the problem could be. I cloned the Laravel 5.5 branch and upgraded to version ^4.0.13 of laravel-mix and successfully ran both yarn dev and yarn prod, although I am using more recent versions of npm and node.
NPM 6.5.0-next.0
Node 11.6.0
Yarn 1.12.3
Here's a GitHub repo to demo.
Update
// TypeError: Cannot read property 'js' of undefined
const { mix } = require('laravel-mix');
// works
const mix = require('laravel-mix');