Ubuntu 17环境下创建文件夹中yarn/npm包安装后消失问题

Hey there, I've run into this exact issue a few times when working with monorepos or fresh project directories—let's break down what's probably happening and how to track down your missing react and react-dom packages:

1. You're likely in a Yarn Workspace (Monorepo Setup) #

Since you're working inside bundler-app/packages/myfolder, it's common for the root bundler-app directory to have a Yarn Workspaces configuration. This setup tells Yarn to install all dependencies from sub-packages into a single node_modules folder at the root of your project (to save space and share dependencies across packages).

• Head up to the bundler-app directory and check if there's a node_modules folder there—your react and react-dom packages are almost certainly inside it.
• Verify this by checking the root package.json for a workspaces field, which will look something like this:

  {
    "workspaces": [
      "packages/*"
    ]
  }
  

This is intentional behavior for monorepos, so don't worry—your packages are safe, just centralized!

2. Your myfolder Directory Doesn't Have a package.json #

Yarn needs a package.json file in the directory where you run yarn add to know where to install local dependencies. If you didn't initialize a package first, Yarn will walk up the directory tree and install the packages in the nearest parent directory that has (or can create) a package.json.

• Check if packages/myfolder has a package.json file. If not:
  1. Run yarn init -y inside myfolder to generate a basic package.json
  2. Re-run yarn add react react-dom—this time, Yarn will create a node_modules folder directly in myfolder and install the packages there.
• If you already checked the root bundler-app directory, you'll probably find a package.json there with react and react-dom listed in its dependencies (Yarn created it automatically when you ran the first install).

3. (Unlikely) Accidental Global Install #

While yarn add defaults to local installation, it's worth ruling out a global install just in case. Run yarn global dir to see where Yarn stores global packages—if you don't see react there, you can cross this off your list.

Quick Recap #

9 times out of 10, your packages are either in the root bundler-app/node_modules (thanks to workspaces) or in a parent directory's node_modules because you didn't initialize a package.json in myfolder. Follow the steps above, and you'll find them in no time!

内容的提问来源于stack exchange，提问作者faraz