Webpack not being recognized after updates - node.js

Question

In my laravel app, after updating to laravel-mix v4, when I run npm run watch, I get the error:
webpack not installed,
consider installing it using npm install
--save-dev webpack
Even when Webpack v4.33.0 is clearly installed & available in my node_modules. 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": {
...
"laravel-mix": "^4.0.16",
"webpack": "^4.33.0"
}
}
Here is my webpack.mix.js:
mix.js('resources/assets/js/app.js','public/js/app.js')
.browserSync({
proxy: 'app.test',
notify: false,
open: true,
port: 8080
})
.options({
extractVueStyles: OUTPUTCSS + 'app.css'
});
This wasn't an issue prior to updating my laravel-mix to v4, what seems to be the issue?
--- UPDATE ---
Here is the npm debug log:
0 info it worked if it ends with ok
1 verbose cli [ '/usr/local/bin/node', '/usr/local/bin/npm', 'run', 'watch' ]
2 info using npm#6.2.0
3 info using node#v10.9.0
4 verbose run-script [ 'prewatch', 'watch', 'postwatch' ]
5 info lifecycle #~prewatch: #
6 info lifecycle #~watch: #
7 verbose lifecycle #~watch: unsafe-perm in lifecycle true
8 verbose lifecycle #~watch: PATH: /usr/local/lib/node_modules/npm/node_modules/npm-lifecycle/node-gyp-bin:/Users/main_user/projects/test_project/node_modules/.bin:/usr/local/bin:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin:/opt/X11/bin
9 verbose lifecycle #~watch: CWD: /Users/main_user/projects/test_project
10 silly lifecycle #~watch: Args: [ '-c', 'npm run development -- --watch' ]
11 silly lifecycle #~watch: Returned: code: 1 signal: null
12 info lifecycle #~watch: Failed to exec watch script
13 verbose stack Error: # watch: `npm run development -- --watch`
13 verbose stack Exit status 1
13 verbose stack at EventEmitter.<anonymous> (/usr/local/lib/node_modules/npm/node_modules/npm-lifecycle/index.js:304:16)
13 verbose stack at EventEmitter.emit (events.js:182:13)
13 verbose stack at ChildProcess.<anonymous> (/usr/local/lib/node_modules/npm/node_modules/npm-lifecycle/lib/spawn.js:55:14)
13 verbose stack at ChildProcess.emit (events.js:182:13)
13 verbose stack at maybeClose (internal/child_process.js:961:16)
13 verbose stack at Process.ChildProcess._handle.onexit (internal/child_process.js:250:5)
14 verbose pkgid #
15 verbose cwd /Users/main_user/projects/test_project
16 verbose Darwin 18.6.0
17 verbose argv "/usr/local/bin/node" "/usr/local/bin/npm" "run" "watch"
18 verbose node v10.9.0
19 verbose npm v6.2.0
20 error code ELIFECYCLE
21 error errno 1
22 error # watch: `npm run development -- --watch`
22 error Exit status 1
23 error Failed at the # watch script.
23 error This is probably not a problem with npm. There is likely additional logging output above.
24 verbose exit [ 1, true ]

Answer 1

Found a similar issue over at webpack/webpack-cli#944
this appears to happen when the webpack.config.js module require()s a missing module or requires are not installed using npm

Answer 2

You can also try change webpack-cli version to 2.1.3
Verify you are not using any deprecated plugins. I had to change GlobCopyWebpackPlugin to CopyWebpackPlugin