如下图所示，使用pnpm安装 antd出现了如下提示
WARN Issues with peer dependencies found
.
├─┬ @testing-library/user-event 13.5.0
│ └── ✕ missing peer @testing-library/dom@>=7.21.4
└─┬ react-scripts 5.0.1
└─┬ eslint-config-react-app 7.0.1
└─┬ eslint-plugin-flowtype 8.0.3
├── ✕ missing peer @babel/plugin-syntax-flow@^7.14.5
└── ✕ missing peer @babel/plugin-transform-react-jsx@^7.14.9
Peer dependencies that should be installed:
@babel/plugin-syntax-flow@^7.14.5
@babel/plugin-transform-react-jsx@^7.14.9
@testing-library/dom@>=7.21.4
怎么回事，那我用npm install antd试一下
npm WARN antd@4.23.2 requires a peer of react@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN antd@4.23.2 requires a peer of react-dom@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN @ant-design/react-slick@0.29.2 requires a peer of react@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-cascader@3.7.0 requires a peer of react@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-cascader@3.7.0 requires a peer of react-dom@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN @ant-design/icons@4.7.0 requires a peer of react@>=16.0.0 but none is installed. You must install peer dependencies yourself.
npm WARN @ant-design/icons@4.7.0 requires a peer of react-dom@>=16.0.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-drawer@5.1.0 requires a peer of react@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-drawer@5.1.0 requires a peer of react-dom@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-checkbox@2.3.2 requires a peer of react@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-checkbox@2.3.2 requires a peer of react-dom@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-collapse@3.3.1 requires a peer of react@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-collapse@3.3.1 requires a peer of react-dom@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-dialog@8.9.0 requires a peer of react@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-dialog@8.9.0 requires a peer of react-dom@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-dropdown@4.0.1 requires a peer of react@>=16.11.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-dropdown@4.0.1 requires a peer of react-dom@>=16.11.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-field-form@1.27.1 requires a peer of react@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-field-form@1.27.1 requires a peer of react-dom@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-picker@2.6.10 requires a peer of react@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-picker@2.6.10 requires a peer of react-dom@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-input@0.1.2 requires a peer of react@>=16.0.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-input@0.1.2 requires a peer of react-dom@>=16.0.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-mentions@1.9.2 requires a peer of react@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-mentions@1.9.2 requires a peer of react-dom@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-notification@4.6.0 requires a peer of react@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-notification@4.6.0 requires a peer of react-dom@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-menu@9.6.4 requires a peer of react@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-menu@9.6.4 requires a peer of react-dom@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-motion@2.6.2 requires a peer of react@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-motion@2.6.2 requires a peer of react-dom@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-select@14.1.13 requires a peer of react@* but none is installed. You must install peer dependencies yourself.
npm WARN rc-select@14.1.13 requires a peer of react-dom@* but none is installed. You must install peer dependencies yourself.
npm WARN rc-pagination@3.1.17 requires a peer of react@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-pagination@3.1.17 requires a peer of react-dom@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-image@5.7.1 requires a peer of react@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-image@5.7.1 requires a peer of react-dom@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-table@7.26.0 requires a peer of react@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-table@7.26.0 requires a peer of react-dom@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-progress@3.3.3 requires a peer of react@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-progress@3.3.3 requires a peer of react-dom@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-rate@2.9.2 requires a peer of react@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-rate@2.9.2 requires a peer of react-dom@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-resize-observer@1.2.0 requires a peer of react@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-resize-observer@1.2.0 requires a peer of react-dom@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-segmented@2.1.0 requires a peer of react@>=16.0.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-segmented@2.1.0 requires a peer of react-dom@>=16.0.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-tree@5.7.0 requires a peer of react@* but none is installed. You must install peer dependencies yourself.
npm WARN rc-tree@5.7.0 requires a peer of react-dom@* but none is installed. You must install peer dependencies yourself.
npm WARN rc-trigger@5.3.1 requires a peer of react@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-trigger@5.3.1 requires a peer of react-dom@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-upload@4.3.4 requires a peer of react@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-upload@4.3.4 requires a peer of react-dom@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-slider@10.0.1 requires a peer of react@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-slider@10.0.1 requires a peer of react-dom@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-steps@4.1.4 requires a peer of react@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-steps@4.1.4 requires a peer of react-dom@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-switch@3.2.2 requires a peer of react@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-switch@3.2.2 requires a peer of react-dom@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-tabs@12.1.0-alpha.1 requires a peer of react@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-tabs@12.1.0-alpha.1 requires a peer of react-dom@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-textarea@0.3.7 requires a peer of react@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-textarea@0.3.7 requires a peer of react-dom@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-tooltip@5.2.2 requires a peer of react@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-tooltip@5.2.2 requires a peer of react-dom@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-tree-select@5.5.0 requires a peer of react@* but none is installed. You must install peer dependencies yourself.
npm WARN rc-tree-select@5.5.0 requires a peer of react-dom@* but none is installed. You must install peer dependencies yourself.
npm WARN rc-util@5.24.4 requires a peer of react@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-util@5.24.4 requires a peer of react-dom@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-input-number@7.3.9 requires a peer of react@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-input-number@7.3.9 requires a peer of react-dom@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-virtual-list@3.4.8 requires a peer of react@* but none is installed. You must install peer dependencies yourself.
npm WARN rc-virtual-list@3.4.8 requires a peer of react-dom@* but none is installed. You must install peer dependencies yourself.
npm WARN rc-overflow@1.2.8 requires a peer of react@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-overflow@1.2.8 requires a peer of react-dom@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-align@4.0.12 requires a peer of react@>=16.9.0 but none is installed. You must install peer dependencies yourself.
npm WARN rc-align@4.0.12 requires a peer of react-dom@>=16.9.0 but none is installed. You must install peer dependencies yourself.
+ antd@4.23.2
added 62 packages from 32 contributors and audited 62 packages in 34.197s
2 packages are looking for funding
run `npm fund` for details
found 0 vulnerabilities
my god，这么多警告，怎么活。
那为了搞清楚这个问题，我们需要先了解PeerDependencies 到底是个什么玩意？搞清楚为什么会missing，为什么这么多WARN？
PeerDependencies 是个什么玩意？
先翻译一下peer：
n.同龄人，同等地位的人，相匹敌的人；（英国）贵族
v.凝视，费力地看；隐现；<古>看见；<古>匹敌
所以翻译成中文应该是叫对等依赖
那再看一下peeDependencies在哪里出现过？
"name": "html-webpack-plugin",
"peerDependencies": {
"webpack": "^5.20.0"
},
"name":"antd",
"peerDependencies": {
"react": ">=16.9.0",
"react-dom": ">=16.9.0"
},
"name":"@testing-library/user-event",
"peerDependencies": {
"@testing-library/dom": ">=7.21.4"
},
First 总结一下：
当我们在一些npm包当中中，用到一些核心的依赖，这些依赖又是跟顶部应用的依赖的一样的时候，会把这些放到peerDependencies当中。而且这个peerDependencies通常在插件当中出现。
Then 问题来了，为什么不能直接把这些依赖直接放到dependencies当中呢？
eg：
想象一下，您正在开发一个ReactApp,他依赖React，有两个插件plugin1,plugin2，他们也依赖React,如果在两个插件中使用dependencies，那么在npm install之后，依赖图是这样的
.
├── ReactApp
│ └── node_modules
│ ├── React
│ ├── plugin1
│ │ └── nodule_modules
│ │ └── React
│ └── plugin2
│ │ └── nodule_modules
│ │ └── React
从上面结构看到，React在顶层已经安装了一次，但是在plugin1 和 plugin2 中又进行了重复的安装，所以被安装了三次。
那这边的peerDependencies就是干这事情的，避免重复安装依赖
如果在plugin1和plugin中使用peerDependencies，那么再执行npm install之后，依赖图是这样的
.
├── ReactApp
│ └── node_modules
│ ├── React
│ ├── plugin1
│ └── plugin2
So, 这时候React包知会被安装一次
当peerDependencies的版本不一致怎么办
But, 如果这个时候plugin1 和plugin2依赖的 React库的版本不一样咋办？ 例如：
"name":"ReactApp",
"dependencies": {
"plugin1":"1.0.0",
"plugin2":"1.0.0",
"react":"18.2.0"
}
"name":"plugin1",
"peerDependencies": {
"react":"16.8.0"
}
"name":"plugin2",
"peerDependencies": {
"react":"18.2.0"
}
这时候，在reactApp下执行npm i 会出现如下警告⚠️？
npm WARN plugin1@1.0.0 requires a peer of react@16.8.0 but none is installed. You must install peer dependencies yourself.
啥，让自己解决？
如何解决版本不一致问题
在 stackoverflow上找到一个回答如下：
OK 我们在demo中尝试一下，
方法一：npm i --save-dev react@16.8.0
, 删掉node_modules目录，重新进行npm i，警告消失了。 但是多了一条这个警告
npm WARN The package react is included as both a dev and production dependency.
方法二： 使用npm-install-peers解决这个问题， 安装好此库之后根目录重新之心npm i，上一条警告消失了。
那为什么这两个方法能够 隐藏 这个问题，不同的版本的react又安装到哪里去了？ 大大的问号？？？ 我没找到，还在研究，有知道大佬的评论区见...
但是以上方法对于使用pnpm安装pnpm i依然有如下报错
ERR_PNPM_PEER_DEP_ISSUES Unmet peer dependencies
.
└─┬ plugin2 1.0.0
└── ✕ unmet peer react@18.2.0: found 16.8.0
hint: If you don't want pnpm to fail on peer dependency issues, add "strict-peer-dependencies=false" to an .npmrc file at the root of your project.
按照提示新建.npmrc文件，输入strict-peer-dependencies=false，重新进行pnpm i，错误变成了如下的WARN。
警告⚠️是啥意思，就是告诉你不一定会报异常，但是也不确定能一定能正常。所以本质上的问题是依然存在，项目依然存在风险。
WARN Issues with peer dependencies found
.
└─┬ plugin2 1.0.0
└── ✕ unmet peer react@18.2.0: found 16.8.0
总结
所以说现在npm，pnpm本身并没很好的办法去解决库当中版本依赖不一致的问题，以上只是隐藏问题，并没有很好解决，终局还需要手动升级包或者插件
如我上面所说，警告⚠️就是告诉你不一定会报异常，但是也不确定能一定能正常。库当中的版本依赖不一致是有可能造成一些不不要的麻烦的，所以你看到如babel-loader, babel这些库在升级版本时候，官方要求多个库同步升级，否则会构建失败。
引申观点
最近有很多vue2的项目想要升级到vue3，但是并不能成功升级到vue3的项目，一方面vue3有了很多破坏性的api，自己本身项目需要进行重构，更夸张的是很多依赖的包是也是依赖vue2去构建的，周边的生态没有跟上vue3的升级速度，并且生态中有很多KPI导向的包留存市面上，维护了一版本之后就再也不维护。so 尤大大也说了，谨慎升级！
老弟曾经也尝试升级过react@15.6项目 到 react@16.8，一些项目成功了，一些项目没有成功，没有成功的项目有一些典型的特征，就是用了过多的开源库，这些开源库强依赖react版本，在react升级之后并没有跟进维护，导致升级失败。
所以在技术选型的时候为什么要选择生态繁荣的，有大公司参与的，大家知道原因了吧！
