Preinstall script to fix npm proxy issues with Yarn and GitHub Package Registry

preinstall.js

// Copyright (c) Alliedstrand Corporation. All rights reserved.
//
// Licensed under the MIT License.

'use strict';

/**
 * @file Extract the GitHub Personal Access Token for GitHub Package Registry
 * access.
 *
 * @note This script should be placed in the root of the repository and added
 * to the "preinstall" script in the `package.json` file. For example,
 * "preinstall": "node preinstall.js --owner=OWNER"
 */

const fs = require('fs');
const os = require('os');
const path = require('path');
const readline = require('readline');

const ownerCLOption = '--owner=';

if (process.argv.length <= 2 || process.argv[2].indexOf(ownerCLOption) !== 0) {
  console.error('Usage: ' + __filename + ` ${ownerCLOption}GITHUB_OWNER`);
  process.exit(-1);
}

const githubOwner = process.argv[2].split(ownerCLOption)[1];

const npmrcFilename = '.npmrc';
const userHomeDirpath = os.homedir();
const userNpmrcFilepath = path.join(userHomeDirpath, npmrcFilename);

const yarnrcFilename = '.yarnrc';

console.info(`INFO: Creating ${yarnrcFilename}...`);

const repoRootFilepath = process.cwd();
const yarnrcFilepath = path.join(repoRootFilepath, yarnrcFilename);

const githubDocLink =
  'See https://help.github.com/en/github/managing-packages-with-github-package-registry/configuring-npm-for-use-with-github-package-registry';

const githubRegUrlPrefix = '//npm.pkg.github.com/:_authToken=';
const githubOwnerRegUrlPrefix = `//npm.pkg.github.com/${githubOwner}/:_authToken=`;

if (!fs.existsSync(userNpmrcFilepath)) {
  console.error(
    `Cannot find ${npmrcFilename} file in ${userHomeDirpath}. Did you run 'npm login' for the GitHub Package Registry.`
  );
  console.error(githubDocLink);
  process.exit(-1);
}

const npmrcReadInterface = readline.createInterface({
  input: fs.createReadStream(userNpmrcFilepath),
});

/**
 * Extract Github Personal Access Token from the user `.npmrc` file.
 * @returns {string | undefined} GitHub token if present. Otherwise,`undefined`.
 */
async function getGithubToken() {
  let token = undefined;

  for await (const line of npmrcReadInterface) {
    if (line.indexOf(githubRegUrlPrefix) === 0) {
      token = line.split(githubRegUrlPrefix)[1];
    }
  }

  return token;
}

getGithubToken().then(function(githubToken) {
  if (githubToken) {
    const yarnrcContents = `${githubRegUrlPrefix}${githubToken}
${githubOwnerRegUrlPrefix}${githubToken}`;

    fs.writeFileSync(yarnrcFilepath, yarnrcContents);
  } else {
    console.error(
      `Cannot find the npm registry URL for the GitHub Package Registry. Did you run 'npm login' for the GitHub Package Registry.`
    );
    console.error(githubDocLink);
    process.exit(-1);
  }
});

console.log(`SUCCESS: Created ${yarnrcFilename}...`);

This script will generate a .yarnrc file in your repository root directory which you should probably add to the .gitignore file as it will be generated before each yarn install and will contain a GitHub user-specific Personal Access Token which you may not wish to check into Git.