从 vue3 和 vite 源码中，我学到了一行代码统一规范团队包管理器的神器

1. 如何学习调试源码
2. 学会 npm 钩子
3. 学会 "preinstall": "npx only-allow pnpm" 一行代码统一规范包管理器
4. 学到 only-allow 原理
5. 等等

// vue-next/package.json
{
  "private": true,
  "version": "3.2.22",
  "scripts": {
    "preinstall": "node ./scripts/preinstall.js",
  }
}

依次执行
# install 之前执行这个脚本
preinstall
# 执行 install 脚本
install
# install 之后执行这个脚本
postinstall

// vue-next/scripts/preinstall.js

if (!/pnpm/.test(process.env.npm_execpath || '')) {
  console.warn(
    `\u001b[33mThis repository requires using pnpm as the package manager ` +
      ` for scripts to work properly.\u001b[39m\n`
  )
  process.exit(1)
}

{
  "scripts": {
    "preinstall": "npx only-allow pnpm -y"
  }
}

# 推荐克隆我的源码库
git clone https://github.com/lxchuan12/only-allow-analysis.git
cd only-allow-analysis/only-allow
# npm i -g pnpm
pnpm i

# 或者克隆官方仓库
git clone https://github.com/pnpm/only-allow.git
cd only-allow
# npm i -g pnpm
pnpm i

{
  "scripts": {
    "preinstall": "npx only-allow yarn"
  }
}

// only-allow/package.json
{
  "bin": "bin.js",
}

// only-allow/package.json
{
  "scripts": {
    "preinstall": "node bin.js pnpm"
  },
}

// only-allow/bin.js
#!/usr/bin/env node
const whichPMRuns = require('which-pm-runs')
// 输出边框盒子
const boxen = require('boxen')

const argv = process.argv.slice(2)
if (argv.length === 0) {
  console.log('Please specify the wanted package manager: only-allow <npm|pnpm|yarn>')
  process.exit(1)
}
// 第一个参数则是 用户传入的希望使用的包管理器
// 比如 npx only-allow pnpm 
// 这里调试是 node bin.js pnpm
const wantedPM = argv[0]
// npm pnpm yarn 都不是，则报错
if (wantedPM !== 'npm' && wantedPM !== 'pnpm' && wantedPM !== 'yarn') {
  console.log(`"${wantedPM}" is not a valid package manager. Available package managers are: npm, pnpm, or yarn.`)
  process.exit(1)
}
// 使用的包管理器
const usedPM = whichPMRuns()
// 希望使用的包管理器 不相等，则报错。
// - npm  提示使用 npm install
// - pnpm 提示使用 pnpm install
// - yarn 提示使用 yarn install
// 最后退出进程
if (usedPM && usedPM.name !== wantedPM) {
  const boxenOpts = { borderColor: 'red', borderStyle: 'double', padding: 1 }
  switch (wantedPM) {
    case 'npm':
      console.log(boxen('Use "npm install" for installation in this project', boxenOpts))
      break
    case 'pnpm':
      console.log(boxen(`Use "pnpm install" for installation in this project.

If you don't have pnpm, install it via "npm i -g pnpm".
For more details, go to https://pnpm.js.org/`, boxenOpts))
      break
    case 'yarn':
      console.log(boxen(`Use "yarn" for installation in this project.

If you don't have Yarn, install it via "npm i -g yarn".
For more details, go to https://yarnpkg.com/`, boxenOpts))
      break
  }
  process.exit(1)
}

'use strict'

module.exports = function () {
  if (!process.env.npm_config_user_agent) {
    return undefined
  }
  return pmFromUserAgent(process.env.npm_config_user_agent)
}

function pmFromUserAgent (userAgent) {
  const pmSpec = userAgent.split(' ')[0]
  const separatorPos = pmSpec.lastIndexOf('/')
  return {
    name: pmSpec.substr(0, separatorPos),
    version: pmSpec.substr(separatorPos + 1)
  }
}