Unable to run `npm install` in fresh Phoenix project on Powershell windows


I am trying to do a Phoenix LiveView project to learn how it works. To this extent, I have, in my windows 10 machine, installed Elixir and NPM via chocolatey. I have also successfully run the commands:

$ mix archive.install hex phx_new
$ mix phx.new demo --live


The problem comes after running the second command. After its completion I am told to follow some additional steps:

We are almost there! The following steps are missing:

    $ cd test_app
    $ cd assets && npm install && node node_modules/webpack/bin/webpack.js --mode development

In specific, the npm install part fails:

> npm install
npm ERR! code ERESOLVE
npm ERR! ERESOLVE unable to resolve dependency tree
npm ERR!
npm ERR! Found: webpack@5.18.0
npm ERR! node_modules/webpack
npm ERR!   dev webpack@"4.41.5" from the root project
npm ERR!   peer webpack@">=2" from babel-loader@8.2.2
npm ERR!   node_modules/babel-loader
npm ERR!     dev babel-loader@"^8.0.0" from the root project
npm ERR!   3 more (copy-webpack-plugin, css-loader, hard-source-webpack-plugin)
npm ERR!
npm ERR! Could not resolve dependency:
npm ERR! dev mini-css-extract-plugin@"^0.9.0" from the root project
npm ERR!
npm ERR! Conflicting peer dependency: webpack@4.46.0
npm ERR! node_modules/webpack
npm ERR!   peer webpack@"^4.4.0" from mini-css-extract-plugin@0.9.0
npm ERR!   node_modules/mini-css-extract-plugin
npm ERR!
npm ERR! Fix the upstream dependency conflict, or retry
npm ERR! this command with --force, or --legacy-peer-deps
npm ERR! to accept an incorrect (and potentially broken) dependency resolution.
npm ERR!
npm ERR! See C:\Users\user\AppData\Local\npm-cache\eresolve-report.txt for a full report.

npm ERR! A complete log of this run can be found in:
npm ERR!     C:\Users\user\AppData\Local\npm-cache\_logs\2021-01-29T08_41_13_010Z-debug.log

This is a fresh project. I am confused as to why this is even happening.
If I run npm install --force then I am greeted with a wall of errors, I assume because of this issue.


How can I fix this?

What is the nodejs version? Probably the recent versions the package.json requires cannot be resolved with the node version requirement. For example, webpack 5.18.0 requires node >= 10.13.0.

I believe my version is recent enough:

> node
Welcome to Node.js v15.6.0.
Type ".help" for more information.

There you go. You’re using node 15, which has npm 7 by default. You’re hitting this issue:

As the issue says, you can workaround the bug with npm i --legacy-peer-deps.

(I also reported the example to the github issue)

So… if you don’t need new feature, then probably better to stick with LTS nodejs and “latest” npm - which is node 14 / npm 6.