问题描述
我全新安装了 yarn(通过 npm install yarn -g)并尝试使用
I have a fresh install of yarn (via npm install yarn -g) and tried to install a few packages with
yarn add vue-loader babel-loader style-loader css-loader file-loader webpack
我在安装过程中收到了一些警告，例如
I got a few warnings during the install, such as
warning "[email protected]" has unmet peer dependency "vue-template-compiler@^2.0.0".
这到底是什么意思，特别是:为什么 yarn 不自行安装这些依赖项?(如果需要的话)
What does this exactly mean, and specifically: why doesn't yarn install these dependencies on its own? (if they are needed)
一个姐妹问题(关于npm) 在同一主题上产生了一些答案，建议 i) 更新 npm ii) 删除 node_modules，因为 npm 中存在错误 关于处理依赖项.
A sister question (about npm) on the same subject yields a few answers which suggest to i) update npm ii) remove node_modules as there is a bug in npm about handling dependencies.
yarn 中此类警告的状态是什么? 我不能丢弃它们(webpack 构建失败)并且必须手动安装它们.同时，安装了相当多的依赖项，所以我不明白为什么遗漏了一些(虽然它们可以手动安装)
What is the status for such warnings in yarn? I cannot discard them (the webpack build fails) and have to manually install them. At the same time, quite a few dependencies were installed so I do not understand why a few were missed (while they are installable manually)
推荐答案
什么是对等依赖
这里是一些关于依赖类型的有用读物，这里是关于对等依赖的信息，但总结一下:
What is a peer dependency
Here is some useful reading on dependency types, and here is info on peer dependencies, but to summarize:
依赖项:您的项目需要运行的库/包.
对等依赖:用于表示您的项目将连接到的库/包.
Dependency: A library/package you project needs to run.
Peer dependency: Used to indicate a library/package your project will hook in to.
vue-loader 包对 vue-template-compiler 有对等依赖 - vue-loader 充当 vue-template-compiler
The package vue-loader has a peer dependency on vue-template-compiler - vue-loader acts as a plugin for vue-template-compiler
对等依赖项会自动安装直到 npm@3(其中纱线跟了进去).由于经常出现令人困惑的行为，这已停止.例如，安装另一个具有冲突要求的插件会导致错误.
Peer dependencies were automatically installed up till npm@3 (which yarn has followed in). This was stopped due to frequently confusing behavior. For example, installing another plugin with a conflicting requirement would result in an error.
我们还将更改 npm@3 中 peerDependencies 的行为.我们将不再自动下载对等依赖项.相反，如果尚未安装对等依赖项，我们会警告您.这需要您自己手动解决 peerDependency 冲突，但从长远来看，这应该可以降低您最终陷入包依赖关系的棘手问题的可能性.[2015 年 2 月 13 日]
更新
根据 此处 npm@7 现在安装对等依赖项.
有关此决定背后的动机，请参阅此处
Update
As per here npm@7 now installs peer dependencies.
For the motivation behind this decision see here
这篇关于使用纱线安装软件包时，“具有未满足的对等依赖性"是什么意思?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！