[Support Guide] Using private NPM modules on Netlify

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Our team figured out a *cough* slightly hacky *cough* way to get this to work with the npm preinstall script.

Create a preinstall script (for example at ./scripts/netlify-preinstall.js):

const fs = require('fs')
const { spawnSync } = require('child_process')

// Netlify does not support Github Packages (or other private package registries besides npm), options are:
//   - Commit .npmrc to repo - However, now we have a secret token inside our repo
//   - Environment variable in .npmrc - However, this requires all developer machines to have the same environment variable configured
//   - Get creative with the preinstall script... :)

// Only run this script on Netlify
if (process.env.NETLIFY === 'true') { // this is a default Netlify environment variable
	// Check if .npmrc already exists, if it does then do nothing (otherwise we create an infinite yarn loop)
	if (!fs.existsSync('.npmrc')) {
		// Create .npmrc
		fs.writeFileSync('.npmrc', `//npm.pkg.github.com/:_authToken=${process.env.GITHUB_TOKEN}\n@oliverit:registry=https://npm.pkg.github.com/\n`)
		fs.chmodSync('.npmrc', 0o600)
		// Run yarn again, because the yarn process which is executing
		// this script won't pick up the .npmrc file we just created.
		// The original yarn process will continue after this second yarn process finishes,
		// and when it does it will report "success Already up-to-date."
		spawnSync('yarn', { stdio: 'inherit' })
	}
}

Configure npm/yarn to run this script before installing dependencies by defining the preinstall script inside the package.json file:

  "scripts": {
    "preinstall": "node ./scripts/netlify-preinstall.js"
  },

Don’t forget to add the GITHUB_TOKEN variable in your Netlify team or site settings.

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