### Yarn Install Output Example

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/blog/2023-10-23-release-4.0.mdx

This snippet shows the improved output of 'yarn install', detailing added packages and their total weight, while reducing noise from peer dependency warnings.

```bash
yarn install

# Example output:
# Success
# Packages added:
#   - @babel/runtime@7.22.11 (10.5 MiB)
#   - react-scripts@5.0.1 (25.3 MiB)
# Done in 1.50s
```

--------------------------------

### Performance Benchmark Setup

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/blog/2023-10-23-release-4.0.mdx

This command sets up a performance benchmark using hyperfine to compare Yarn versions by installing Gatsby and its dependencies from a cold cache.

```bash
hyperfine -L v stable,canary --prepare 'rm -rf ~/.yarn/berry/cache' 'cd $(mktemp -d) && yarn init -2 && yarn set version {v} && yarn && yarn add gatsby --mode=skip-build'
```

--------------------------------

### Start Development Server

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/README.md

Starts a local development server for live previewing changes. Changes are reflected without server restart.

```bash
yarn start
```

--------------------------------

### Install @yarnpkg/pnpify

Source: https://github.com/yarnpkg/berry/blob/master/packages/yarnpkg-pnpify/README.md

Install the pnpify CLI tool as a development dependency.

```bash
yarn add -D @yarnpkg/pnpify
```

--------------------------------

### Install Yarn from Source

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/docs/getting-started/basics/install.mdx

Install the latest Yarn build directly from the repository. This method does not use Corepack and stores the binary locally.

```bash
yarn set version from sources
```

--------------------------------

### Normalized Configuration Example

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/blog/2020-01-24-release-2.0.mdx

Presents an example of the .yarnrc.yml file, highlighting the unified configuration system in Yarn 2.

```yaml
initScope: yarnpkg
npmPublishAccess: public
yarnPath: scripts/run-yarn.js

```

--------------------------------

### Install @yarnpkg/extensions

Source: https://github.com/yarnpkg/berry/blob/master/packages/yarnpkg-extensions/README.md

Install the @yarnpkg/extensions package using Yarn.

```bash
yarn add @yarnpkg/extensions
```

--------------------------------

### Install Dependencies with Yarn

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/docs/getting-started/basics/usage.mdx

Run `yarn` to install project dependencies. This command is an alias for `yarn install`.

```bash
yarn
```

--------------------------------

### Install @yarnpkg/sdks

Source: https://github.com/yarnpkg/berry/blob/master/packages/yarnpkg-sdks/README.md

Install the SDKs package as a development dependency using Yarn.

```bash
yarn add -D @yarnpkg/sdks
```

--------------------------------

### Update All Installed SDKs and Editor Settings

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/docs/getting-started/extra/editor-sdks.mdx

Run this command to update all installed SDKs and their corresponding editor settings.

```bash
yarn dlx @yarnpkg/sdks
```

--------------------------------

### Generate Hello World Package Files

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/docs/advanced/01-general-reference/protocols/exec.mdx

Example of generating a simple 'hello-world' package by writing `package.json` and `index.js` to the build directory.

```typescript
fs.writeFileSync(path.join(execEnv.buildDir, 'package.json'), JSON.stringify({
  name: 'hello-world',
  version: '1.0.0',
}));

fs.writeFileSync(path.join(execEnv.buildDir, 'index.js'), "
  module.exports = 'hello world!';
");
```

--------------------------------

### Start Local Docusaurus Server

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/docs/advanced/04-technical/contributing.mdx

Run this command to start a local development server for the Docusaurus documentation website. This allows you to preview your documentation changes in real-time.

```bash
yarn start

```

--------------------------------

### Initialize New Project with Yarn

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/docs/getting-started/basics/install.mdx

Initialize a new project with Yarn version 2 or higher. This command requires Corepack to be installed.

```bash
yarn init -2
```

--------------------------------

### Yarn Config Command Example

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/blog/2023-10-23-release-4.0.mdx

Demonstrates the new tree display and positional argument support for the 'yarn config' command, allowing focused viewing of specific settings.

```bash
yarn config

# Example output:
# yarn config v3.6.4
# yarn config v4.0.0
# 
# 
#   nodeLinker: "node-modules"
#   # ... other config settings
# 
# Done in 1.50s
```

--------------------------------

### Initialize a new library within a monorepo

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/docs/getting-started/extra/recipes.mdx

Start a new library in a monorepo by running the 'init' command in the target directory without manual folder creation.

```bash
yarn packages/my-new-lib init
```

--------------------------------

### Yarn Doctor Output Example

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/docs/getting-started/migrating/pnp.mdx

Example output from the Yarn Doctor tool, highlighting issues like undeclared dependencies and unsafe references to node_modules.

```text
➤ YN0000: Found 1 package(s) to process
➤ YN0000: For a grand total of 236 file(s) to validate

➤ YN0000: ┌ /webpack-dev-server/package.json
➤ YN0000: │ /webpack-dev-server/test/testSequencer.js:5:19: Undeclared dependency on @jest/test-sequencer
➤ YN0000: │ /webpack-dev-server/client-src/default/webpack.config.js:12:14: Webpack configs from non-private packages should avoid referencing loaders without require.resolve
➤ YN0000: │ /webpack-dev-server/test/server/contentBase-option.test.js:68:8: Strings should avoid referencing the node_modules directory (prefer require.resolve)
➤ YN0000: └ Completed in 5.12s

➤ YN0000: Failed with errors in 5.12s
```

--------------------------------

### Install Yarn Canary Build

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/docs/getting-started/basics/install.mdx

Use this command to install a Release Candidate build of Yarn, which may include features not yet available on the stable channel.

```bash
yarn set version canary
```

--------------------------------

### Correct module import usage

Source: https://github.com/yarnpkg/berry/blob/master/packages/yarnpkg-doctor/README.md

This example shows the correct way to import a module by its name, which is compatible with Plug'n'Play. This is the preferred method over referencing 'node_modules' directly.

```javascript
var foo = require("lodash"); // importing a module by its name
```

--------------------------------

### Install Git Workspace with Tag

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/docs/advanced/01-general-reference/protocols/git.mdx

Clone a Git repository and install a specific workspace, pinning it to a tag. Requires the remote repository to use Yarn or npm (v7+).

```bash
git@github.com:yarnpkg/berry.git#workspace=@yarnpkg/shell&tag=@yarnpkg/shell/2.1.0
```

--------------------------------

### Install Corepack

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/docs/getting-started/basics/install.mdx

Install Corepack globally using npm. This tool manages package manager versions.

```bash
npm install -g corepack
```

--------------------------------

### Install Yarn from Specific Source Branch

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/docs/getting-started/basics/install.mdx

Install a specific version of Yarn from a particular branch or pull request in the repository. This is useful for testing.

```bash
yarn set version from sources --branch 1211
```

--------------------------------

### Integrate Corepack with Volta

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/docs/getting-started/extra/corepack.mdx

Installs Corepack globally and enables it with a specific install directory to ensure it overwrites Volta's Yarn shims, forcing integration.

```bash
npm install -g corepack

# Specifying an explicit install-directory makes corepack overwrite volta's yarn shims, which is what we want
corepack enable --install-directory "~/.volta/bin"
```

--------------------------------

### Virtual Folder Path Examples

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/docs/advanced/03-pnp/pnp-spec.mdx

Illustrates the transformation of virtual folder paths to their concrete file paths. The '__virtual__/<hash>/<n>' segment is processed to derive the final path.

```text
/path/to/some/folder/__virtual__/a0b1c2d3/0/subpath/to/file.dat
/path/to/some/folder/subpath/to/file.dat
```

```text
/path/to/some/folder/__virtual__/e4f5a0b1/0/subpath/to/file.dat
/path/to/some/folder/subpath/to/file.dat (different hash, same result)
```

```text
/path/to/some/folder/__virtual__/a0b1c2d3/1/subpath/to/file.dat
/path/to/some/subpath/to/file.dat
```

```text
/path/to/some/folder/__virtual__/a0b1c2d3/3/subpath/to/file.dat
/path/subpath/to/file.dat
```

--------------------------------

### Clone Monorepo, Build, and Pack Workspace

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/docs/advanced/01-general-reference/protocols/exec.mdx

Demonstrates cloning a git repository, installing its dependencies, packing a specific workspace, and extracting its contents to the build directory.

```typescript
const pathToRepo = path.join(execEnv.tempDir, 'repo');
const pathToArchive = path.join(execEnv.tempDir, 'archive.tgz');
const pathToSubpackage = path.join(pathToRepo, 'packages/foobar');

// Clone the repository
child_process.execFileSync(`git`, [`clone`, `git@github.com:foo/bar`, pathToRepo]);

// Install the dependencies
child_process.execFileSync(`yarn`, [`install`], {cwd: pathToRepo});

// Pack a specific workspace
child_process.execFileSync(`yarn`, [`pack`, `--out`, pathToArchive], {cwd: pathToSubpackage});

// Send the package content into the build directory
child_process.execFileSync(`tar`, [`-x`, `-z`, `--strip-components=1`, `-f`, pathToArchive, `-C`, execEnv.buildDir]);
```

--------------------------------

### Example of instantiating WorkspaceCwd in Prolog

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/docs/advanced/01-general-reference/error-codes.mdx

Demonstrates how to correctly instantiate the WorkspaceCwd parameter before using it in a predicate like workspace_field. This prevents Prolog instantiation errors.

```prolog
workspace_field(WorkspaceCwd, 'name', _).

```

```prolog
workspace(WorkspaceCwd), workspace_field(WorkspaceCwd, 'name', _).

```

--------------------------------

### Calling Binaries with yarn run bin

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/docs/getting-started/migrating/pnp.mdx

Instead of relying on `node_modules/.bin`, use `yarn run bin` or its shortcut `yarn` to execute binaries. This command works seamlessly with PnP installations.

```bash
yarn run jest
```

```bash
# or, using the shortcut:
yarn jest
```

--------------------------------

### Install Dependencies and Pick Up Source Changes

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/docs/advanced/04-technical/contributing.mdx

Run this command within the Yarn repository to install dependencies. It automatically picks up changes made to the TypeScript sources without requiring a separate build step.

```bash
yarn install # Will automatically pick up any changes you made to sources
```

--------------------------------

### Check Corepack Status

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/docs/getting-started/extra/corepack.mdx

Verifies if Corepack is enabled and correctly installed by checking for the COREPACK_ROOT environment variable. A path output indicates successful installation.

```bash
yarn exec env | grep COREPACK_ROOT
```

--------------------------------

### New Lockfile Format Example

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/blog/2020-01-24-release-2.0.mdx

Illustrates the new pure YAML format for Yarn 2's lockfile and configuration files, replacing the older custom format.

```yaml
"@yarnpkg/parsers@workspace:^2.0.0-rc.6, @yarnpkg/parsers@workspace:packages/yarnpkg-parsers":
  version: 0.0.0-use.local
  resolution: "@yarnpkg/parsers@workspace:packages/yarnpkg-parsers"
  dependencies:
    js-yaml: ^3.10.0
    pegjs: ^0.10.0
  languageName: unknown
  linkType: soft

```

--------------------------------

### Use 'pnpm' Node Linker

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/blog/2021-09-25-release-3.1.mdx

Switch to a symlink-based installation strategy by setting 'nodeLinker' to 'pnpm' in your .yarnrc.yml. This mimics the installation method used by the pnpm package manager.

```yaml
nodeLinker: pnpm
```

--------------------------------

### Configure Supported Architectures for Conditional Packages

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/blog/2021-09-25-release-3.1.mdx

Manually define the operating systems and CPU architectures for which packages should be fetched and installed. This is particularly useful for zero-install scenarios requiring a strict set of supported environments.

```yaml
supportedArchitectures:
  os: [linux, darwin]
  cpu: [x64, arm64]
```

--------------------------------

### Add PnPify Dependency

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/docs/advanced/03-pnp/pnpify.mdx

Install PnPify as a project dependency using Yarn.

```bash
yarn add @yarnpkg/pnpify
```

--------------------------------

### Yarn Workspaces Focus Command

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/blog/2020-07-09-release-2.1.mdx

The `yarn workspaces focus` command installs dependencies for a specific workspace and its direct dependencies. This is useful for reducing install size, especially when integrating monorepos with Docker images using the `--production` flag.

```bash
yarn workspaces focus <workspace-name>
```

```bash
yarn workspaces focus <workspace-name> --production
```

--------------------------------

### Explain Peer Dependencies

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/docs/advanced/01-general-reference/error-codes.mdx

Use this command to get detailed information about peer dependency resolution issues. Pass the 'p'-prefixed code from the original error message to this command.

```bash
yarn explain peer-requirements pf649c
```

--------------------------------

### Normalized Shell Scripts Example

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/blog/2020-01-24-release-2.0.mdx

Demonstrates how Yarn 2's shell interpreter handles script fields, ensuring compatibility across different operating systems.

```json
{
  "scripts": {
    "redirect": "node ./something.js > hello.md",
    "no-cross-env": "NODE_ENV=prod webpack"
  }
}
```

--------------------------------

### Add TypeScript and enable VSCode integration

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/docs/getting-started/extra/recipes.mdx

Install TypeScript as a development dependency and enable VSCode integration for enhanced developer experience.

```bash
yarn add --dev typescript
yarn dlx @yarnpkg/sdks vscode
```

--------------------------------

### Build Dependency Tracking Example

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/blog/2020-01-24-release-2.0.mdx

This log output shows Yarn 2's build dependency tracking in action, indicating that the 'sharp' package needed to be rebuilt because its dependency tree changed.

```bash
➤ YN0000: ┌ Link step
➤ YN0007: │ sharp@npm:0.23.0 must be rebuilt because its dependency tree changed
➤ YN0000: └ Completed in 16.92s
➤ YN0000: Done with warnings in 21.07s
```

--------------------------------

### Accessing Files with @yarnpkg/fslib

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/docs/advanced/03-pnp/pnp-api.mdx

Use @yarnpkg/fslib to access files, including those within zip archives. This example demonstrates setting up PosixFS and ZipOpenFS for cross-platform compatibility.

```ts
const {PosixFS, ZipOpenFS} = require(`@yarnpkg/fslib`);
const libzip = require(`@yarnpkg/libzip`).getLibzipSync();

// This will transparently open zip archives
const zipOpenFs = new ZipOpenFS({libzip});

// This will convert all paths into a Posix variant, required for cross-platform compatibility
const crossFs = new PosixFS(zipOpenFs);

console.log(crossFs.readFileSync(`C:\\path\\to\\archive.zip\\package.json`));
```

--------------------------------

### Generator Script for Exec Protocol

Source: https://github.com/yarnpkg/berry/blob/master/packages/plugin-exec/README.md

Example Node.js script used with the `exec:` protocol. It populates the `buildDir` with `package.json` and `index.js` files using the provided `execEnv` global.

```javascript
const {buildDir} = execEnv;

fs.writeFileSync(path.join(buildDir, `package.json`), JSON.stringify({
  name: `pkg`,
  version: `1.0.0`,
}));

fs.writeFileSync(path.join(buildDir, `index.js`), `module.exports = ${Date.now()};
`);
```

--------------------------------

### Configuring Yarn Cache Folder via CLI (Deprecated)

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/docs/advanced/01-general-reference/error-codes.mdx

This example shows a deprecated way of passing CLI options like `--cache-folder`. Yarn v2+ consolidates configuration in `.yarnrc.yml` files.

```bash
yarn install --cache-folder .yarn
```

--------------------------------

### Performance Benchmark Results

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/blog/2023-10-23-release-4.0.mdx

Shows the benchmark results comparing Yarn 3.6.0 and Yarn 4.0.0 for installing Gatsby, highlighting a 3.92x speed improvement with Yarn 4.0.0.

```js
Benchmark 1: 3.6.0
  Time (mean ± σ):     65.599 s ±  2.214 s    [User: 82.952 s, System: 8.638 s]
  Range (min … max):   62.167 s … 68.277 s    10 runs

Benchmark 2: 4.0.0
  Time (mean ± σ):     16.724 s ±  0.928 s    [User: 14.622 s, System: 5.743 s]
  Range (min … max):   15.318 s … 18.110 s    10 runs

Summary
  4.0.0 ran 3.92 ± 0.25 times faster than 3.6.0
```

--------------------------------

### Executing Binaries with Yarn bin

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/docs/advanced/02-package-management/rulebook.mdx

When needing to execute a binary from a dependency, especially with specific Node flags, use `yarn bin <binary_name>` to get its path. This is an alternative to relying on the `node_modules/.bin` folder directly.

```bash
yarn node --inspect $(yarn bin jest)
```

--------------------------------

### Using findPnpApi to Get PnP API Instance

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/docs/advanced/03-pnp/pnp-api.mdx

Shows how to use the findPnpApi function from the 'module' builtin to locate and load the closest .pnp.cjs file. It's important to use createRequire to load resolved modules.

```javascript
const {createRequire, findPnpApi} = require(`module`);

// We'll be able to inspect the dependencies of the module passed as first argument
const targetModule = process.argv[2];

const targetPnp = findPnpApi(targetModule);
const targetRequire = createRequire(targetModule);

const resolved = targetPnp.resolveRequest(`eslint`, targetModule);
const instance = targetRequire(resolved); // <-- important! don't use `require`!
```

--------------------------------

### Generate Editor SDKs and Settings

Source: https://github.com/yarnpkg/berry/blob/master/packages/yarnpkg-sdks/README.md

Use the 'sdks' command to generate editor SDKs and associated settings for your project.

```bash
yarn sdks
```

--------------------------------

### Generate Hello World Package

Source: https://github.com/yarnpkg/berry/blob/master/packages/plugin-exec/README.md

Creates a new package with a package.json and an index.js file. Ensure the build directory is set up before execution.

```typescript
fs.writeFileSync(path.join(execEnv.buildDir, 'package.json'), JSON.stringify({
  name: 'hello-world',
  version: '1.0.0',
}));

fs.writeFileSync(path.join(execEnv.buildDir, 'index.js'), `
  module.exports = 'hello world!';
`);
```

--------------------------------

### Register a Simple Command

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/docs/advanced/04-technical/plugin-tutorial.mdx

Defines a basic command 'hello' for your plugin. No external dependencies are needed for this basic command.

```javascript
module.exports = {
  name: `plugin-hello-world`,
  factory: require => {
    const {BaseCommand} = require(`@yarnpkg/cli`);

    class HelloWorldCommand extends BaseCommand {
      static paths = [[`hello`]];

      async execute() {
        this.context.stdout.write(`This is my very own plugin 😎\n`);
      }
    }

    return {
      commands: [
        HelloWorldCommand,
      ],
    };
  }
};

```

--------------------------------

### Create a directory for node_modules project

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/docs/getting-started/extra/recipes.mdx

Set up a new directory and an empty yarn.lock file for a project that will use node_modules.

```bash
mkdir nm-packages/myproj
touch nm-packages/myproj/yarn.lock
```

--------------------------------

### Parse Bare Identifier

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/docs/advanced/03-pnp/pnp-spec.mdx

Parses a module specifier into its scoped identifier (if any) and module path. Handles scoped packages starting with '@'.

```javascript
PARSE_BARE_IDENTIFIER(specifier)
```

--------------------------------

### PNP_RESOLVE Algorithm Step 1-3

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/docs/advanced/03-pnp/pnp-spec.mdx

The initial steps of the PNP_RESOLVE algorithm, handling Node.js builtins and local/absolute paths.

```text
PNP_RESOLVE(specifier, parentURL)

1. Let `resolved` be **undefined**

2. If `specifier` is a Node.js builtin, then

    1. Set `resolved` to `specifier` itself and return it

3. Otherwise, if `specifier` is either an absolute path or a path prefixed with "./" or "../", then

    1. Set `resolved` to [`NM_RESOLVE`](#nm_resolve)`(specifier, parentURL)` and return it
```

--------------------------------

### Build Static Website

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/README.md

Generates the static content for the website into the 'build' directory, ready for deployment.

```bash
yarn build
```

--------------------------------

### Checking for PnP Environment

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/docs/advanced/03-pnp/pnp-api.mdx

Demonstrates how to check if the current environment is running under Plug'n'Play by inspecting process.versions.pnp. This is useful for conditionally applying PnP-specific logic.

```javascript
if (process.versions.pnp) {
  // do something with the PnP API ...
} else {
  // fallback
}
```

--------------------------------

### List Changed Workspaces

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/blog/2021-09-25-release-3.1.mdx

Get a list of workspaces that have changed compared to the main branch. Useful for scripting purposes or identifying modified packages.

```bash
yarn workspaces list --since
```

--------------------------------

### Update Yarn to Latest Stable Version

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/docs/getting-started/basics/install.mdx

Update your project to use the most recent stable Yarn binary. This involves setting the version and then installing dependencies.

```bash
yarn set version stable
yarn install
```

--------------------------------

### Get Package Information

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/docs/advanced/03-pnp/pnp-api.mdx

Retrieves all stored information for a given package locator from the PnP API. This includes details about the package's dependencies and resolution.

```typescript
export function getPackageInformation(locator: PackageLocator): PackageInformation;
```

--------------------------------

### Add a package using the Portal Protocol

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/docs/advanced/01-general-reference/protocols/portal.mdx

Use the portal: protocol to add a local package dependency. The target path must be relative and the package must exist at resolution time.

```bash
yarn add react-dom@portal:./my-react-dom
```

--------------------------------

### Enable Postinstall Scripts Per Package

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/docs/features/security.mdx

You can enable postinstall scripts for specific packages by using the `dependenciesMeta` field in your top-level `package.json`. This allows granular control over which packages can run postinstall scripts.

```json
{
  "dependenciesMeta": {
    "my-package": {
      "builtin": true,
      "root": true
    }
  }
}
```

--------------------------------

### Auto-updating Dependencies Example

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/docs/features/release-workflow.mdx

Demonstrates how Yarn automatically updates dependent package versions within a monorepo when a package is upgraded. This applies to basic semver ranges.

```text
/packages/common (1.0.0)
/packages/server (depends on common@^1.0.0)
/packages/client (depends on common@^1.0.0)
```

```text
/packages/common (1.1.1)
/packages/server (depends on common@^1.1.1)
/packages/client (depends on common@^1.1.1)
```

--------------------------------

### Find Package Locator by Disk Location

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/docs/advanced/03-pnp/pnp-api.mdx

Use `findPackageLocator` to get the package locator for a given disk path. This function always returns physical locators.

```typescript
export function findPackageLocator(location: string): PackageLocator | null;
```

--------------------------------

### Build Yarn CLI

Source: https://github.com/yarnpkg/berry/blob/master/README.md

Run this command after cloning the repository to build the Yarn CLI. Your global Yarn will then use the locally built version.

```bash
yarn build:cli
```

--------------------------------

### Check Package Versions for Release (Interactive)

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/docs/advanced/04-technical/contributing.mdx

Interactively select packages that need to be released and specify their new versions. This is a required step for preparing a PR for release.

```bash
yarn version check --interactive
```

--------------------------------

### Run Command with Pnpify

Source: https://github.com/yarnpkg/berry/blob/master/packages/yarnpkg-pnpify/README.md

Execute a command using the pnpify CLI, which creates a virtual node_modules folder for the command's execution context.

```bash
pnpify run <command>
```

--------------------------------

### Get Package Locator Helper

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/docs/advanced/03-pnp/pnp-api.mdx

A helper function to simplify working with 'referencish' ranges for package dependencies. It handles the logic for resolving locators from string or tuple references.

```typescript
export function getLocator(name: string, referencish: string | [string, string]): PackageLocator;
```

--------------------------------

### Register a Hook to Modify Script Environment

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/docs/advanced/04-technical/plugin-tutorial.mdx

Listens to the 'setupScriptEnvironment' hook to inject a custom environment variable 'HELLO_WORLD'. This allows plugins to influence script execution.

```javascript
module.exports = {
  name: `plugin-hello-world`,
  factory: require => ({
    hooks: {
      setupScriptEnvironment(project, scriptEnv) {
        scriptEnv.HELLO_WORLD = `my first plugin!`;
      },
    },
  })
};

```

--------------------------------

### Define a basic catalog in .yarnrc.yml

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/docs/features/catalogs.mdx

Define version ranges for dependencies in your `.yarnrc.yml` file. This serves as a central source of truth for dependency versions.

```yaml
catalog:
  react: ^18.3.1
  lodash: ^4.17.21
```

--------------------------------

### Add Package with Automatic @types Resolution

Source: https://github.com/yarnpkg/berry/blob/master/packages/plugin-typescript/README.md

Demonstrates how Yarn automatically adds the corresponding @types package when a new package is installed. This is useful for ensuring type safety in TypeScript projects.

```bash
❯ yarn/packages/plugin-typescript ❯ yarn add lodash

➤ YN0000: · Yarn X.Y.Z
➤ YN0000: ┌ Resolution step
➤ YN0000: └ Completed in 0.24s
➤ YN0000: ┌ Fetch step
➤ YN0013: │ @types/lodash@npm:4.14.121 can't be found in the cache and will be fetched from the remote registry
➤ YN0013: │ lodash@npm:4.14.0 can't be found in the cache and will be fetched from the remote registry
➤ YN0000: └ Completed in 3.63s
➤ YN0000: ┌ Link step
➤ YN0000: └ Completed in 2.75s
➤ YN0000: · Done with warnings in 6.81s
```

--------------------------------

### Enable Hardened Mode via Environment Variable

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/blog/2023-10-23-release-4.0.mdx

For CI jobs or specific environments, enable Hardened Mode by setting this environment variable. Note that this mode significantly slows down installs.

```bash
export YARN_ENABLE_HARDENED_MODE=1
```

--------------------------------

### Incorrect node_modules string usage

Source: https://github.com/yarnpkg/berry/blob/master/packages/yarnpkg-doctor/README.md

This example demonstrates an incorrect usage of 'node_modules' within a require statement. Such patterns are flagged by the 'no node module strings' rule as they are incompatible with Plug'n'Play.

```javascript
var module = require("../node_modules/lodash");
```

--------------------------------

### Implement `afterAllInstalled` Hook

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/docs/advanced/04-technical/plugin-tutorial.mdx

This snippet shows how to implement the `afterAllInstalled` hook to log the number of non-virtual descriptors and packages in a project. It accesses the `Project` instance provided by Yarn.

```javascript
const fs = require(`fs`);
const util = require(`util`);

module.exports = {
  name: `plugin-project-info`,
  factory: require => {
    const {structUtils} = require(`@yarnpkg/core`);

    return {
      default: {
        hooks: {
          afterAllInstalled(project) {
            let descriptorCount = 0;
            for (const descriptor of project.storedDescriptors.values())
              if (!structUtils.isVirtualDescriptor(descriptor))
                descriptorCount += 1;

            let packageCount = 0;
            for (const pkg of project.storedPackages.values())
              if (!structUtils.isVirtualLocator(pkg))
                packageCount += 1;

            console.log(`This project contains ${descriptorCount} different descriptors that resolve to ${packageCount} packages`);
          }
        }
      }
    };
  }
};

```

--------------------------------

### Generate Editor SDKs with Yarn dlx

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/docs/getting-started/extra/editor-sdks.mdx

Use this command to generate the base SDK and specific editor settings for VSCode, Vim, and other supported tools.

```bash
yarn dlx @yarnpkg/sdks vscode vim ...
```

--------------------------------

### Enforcing Strict Package Boundaries

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/blog/2020-01-24-release-2.0.mdx

This example shows an error that occurs when an application tries to access a package not declared in its dependencies. Ensure all required packages are listed in your project's dependencies.

```typescript
// Error: Something that got detected as your top-level application
// (because it doesn't seem to belong to any package) tried to access
// a package that is not declared in your dependencies
//
// Required package: not-a-dependency (via "not-a-dependency")
// Required by: /Users/mael/my-app/
require(`not-a-dependency`);
```

--------------------------------

### Check Package Versions for Release

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/docs/advanced/04-technical/contributing.mdx

Verify that all package versions are correctly set for release. This command checks the current release status.

```bash
yarn version check
```

--------------------------------

### Deferred Version Record Example

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/docs/features/release-workflow.mdx

Illustrates the format of the internal record created by Yarn when using deferred versioning. This YAML file stores pending upgrades within the .yarn/versions directory.

```yaml
releases:
  my-package@1.0.0: minor
```

--------------------------------

### Add a package with a patch protocol

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/docs/advanced/01-general-reference/protocols/patch.mdx

Use the `patch:` protocol to add a package with a specific patch applied. The format includes the original package version and the path to the patch file.

```bash
yarn add @types/react@patch:@types/react@18.0.0#./my-patches/react-types.patch
```