Yarn

https://github.com/yarnpkg/berry
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### Start local development server with yarn start

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

Starts a local development server and opens a browser window. Most changes are reflected live without restarting the server.

```bash
$ yarn start
```

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

### Install Yarn from sources

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

Clone, build, and install Yarn from the repository source.

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

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

### Virtual folder path resolution examples

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

Examples showing how virtual folder paths resolve to concrete paths, with different hashes and n values.

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

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

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

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

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

### Install Corepack

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

Install Corepack globally using npm.

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

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

### Call binaries with yarn run bin

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

Use yarn run bin to start scripts and binaries instead of relying on node_modules/.bin, which is not generated in PnP installs. The shortcut yarn jest works as well.

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

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

### patch: protocol example

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

Example of using the patch: protocol in a package.json dependencies field.

```json
{
  "dependencies": {
    "left-pad": "patch:left-pad@1.3.0#./my-patch.patch"
  }
}
```

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

### Example .yarnrc.yml Configuration

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

A sample configuration file demonstrating the unified settings format used in Yarn 2.

```yml
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 to access package extensions that fix known issues in the ecosystem.

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

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

### Enable Corepack and check installation

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

Run `corepack enable` to activate Corepack, which is included with Node.js 14.19 / 16.9 and later but opt-in during the experimental stage. Verify it's working by running `yarn exec env | grep COREPACK_ROOT`; a path in the output indicates Corepack is properly installed.

```bash
corepack enable
```

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

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

### Install dependencies and use development sources

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

Run `yarn install` in the repository to pick up any changes made to the TypeScript sources. The repository is configured to use the sources directly without rebuilding.

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

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

### Install Yarn from a specific branch

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

Install Yarn from a specific branch or PR.

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

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

### yarn workspaces foreach

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

Example of running a command across all workspaces using the workspace-tools plugin.

```shell
$ yarn workspaces foreach run build
```

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

### Run local docs server with 'yarn start'

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

Spawns a local Docusaurus server to preview documentation changes. Run this from the repository root (packages/docusaurus) to see your .mdx edits live.

```bash
yarn start

```

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

### Run hyperfine benchmark for Yarn install performance

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

Benchmark command used to compare Yarn 3.6.0 and 4.0.0 install times on a cold cache. It removes the cache, creates a temporary directory, initializes a project, sets the Yarn version, installs dependencies, and adds Gatsby with skip-build mode.

```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'
```

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

### Update all SDKs and editor settings

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

Updates all installed SDKs and editor settings.

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

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

### Initialize a new library inside a monorepo with yarn packages/my-new-lib init

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

Runs the `init` command within `packages/my-new-lib` to start a new library without manually creating directories. Useful for monorepos.

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

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

### npx vs yarn dlx

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

Examples showing the difference between npx and yarn dlx commands.

```shell
$ npx serv # Oops, should have been "serve"
```

```shell
$ yarn dlx terser my-file.js
$ yarn run serve
$ yarn serve
```

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

### Run a binary with Node flags using yarn bin or yarn run

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

Run a binary with Node flags without hardcoding node_modules/.bin. The first uses yarn bin to get the path; the second uses yarn run's --inspect flag as a simpler alternative.

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

```text
yarn run --inspect jest
```

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

### Sample Yarn 2 YAML lockfile entry

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

Shows an example lockfile entry in pure YAML format for the @yarnpkg/parsers package with version, resolution, dependencies, and metadata. Illustrates the new YAML syntax used in lock and configuration files.

```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
```

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

### Update Yarn to stable

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

Update Yarn to the latest stable version and install dependencies.

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

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

### Example .yarn/versions record

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

Shows the YAML format of a deferred version record. The key is the package name and current version, and the value is the release type (e.g., minor).

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

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

### Add @yarnpkg/pnpify to dependencies

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

Install the PnPify package as a dependency to enable running incompatible tools with PnP.

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

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

### Publishing replaces catalog: with actual version ranges

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

When publishing, the `catalog:` protocol is automatically replaced with the actual version range, ensuring compatibility with other package managers. The example shows the source and published `package.json`.

```json
{
  "dependencies": {
    "react": "catalog:react18"
  }
}
```

```json
{
  "dependencies": {
    "react": "^18.3.1"
  }
}
```

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

### Clone a monorepo and build a specific package with exec: protocol

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

Clones a monorepo, installs dependencies, packs a specific workspace, and extracts it into execEnv.buildDir. Uses execEnv.tempDir for temporary files and execEnv.buildDir for the final package content.

```ts
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]);
```

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

### Explain peer dependencies with yarn explain peer-requirements

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 errors. Pass the 'p'-prefixed code from the original error message.

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

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

### Define cross-platform scripts in Yarn 2

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

Shows two example scripts that rely on Yarn 2's normalized shell for cross-platform compatibility with a redirected output to a file and setting an environment variable. This permits the same scripts to work on Windows and macOS/Linux without tools like cross-env.

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

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

### Add a package from a git repository

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

Use this command to add a package directly from a git repository when the package is not published to the npm registry. The git protocol fetches the repository and packs it before installation.

```bash
yarn add typanion@git@github.com/arcanis/typanion.git
```

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

### Yarn output showing rebuild due to dependency tree change

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

Example output from Yarn 2 showing that a package with a postinstall script is rebuilt only when its dependency tree changes. Here `sharp@npm:0.23.0` is rebuilt because its dependency tree changed, and the command finishes with warnings.

```text
➤ 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
```

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

### Improved peer dependency warning

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/blog/2020-11-30-release-2.4.mdx

Example of the improved peer dependency warning in Yarn 2.4. It includes a hash (pXYZ) that can be used with `yarn explain peer-requirements <hash>` to get the exact list of packages contributing to the requirement.

```text
your project provides react@17 (pXYZ), which doesn't satisfy what @storybook-react and its dependents request
```

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

### Initialize a new project

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

Initialize a new Yarn project with version 2.

```bash
yarn init -2
```

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

### Generate a hello-world package with exec: protocol

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

Generates a simple hello-world package by writing package.json and index.js into execEnv.buildDir. The script runs in a special context where Node builtins like fs are available globally.

```ts
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!';
`);
```

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

### Locate and load dependencies with findPnpApi and createRequire

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

Demonstrates using findPnpApi to resolve a dependency and createRequire to load it correctly.

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

// We'll be able to inspect the dependencies of the module passed as first argument
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`!
```

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

### Strict Package Boundary Error Example

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

An example of the error message generated when attempting to require a package not listed in the dependencies.

```ts
// 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`);
```

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

### Set nodeLinker to pnpm in .yarnrc.yml

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

Use symlink-based installs by setting nodeLinker to pnpm. This is a new install mode in Yarn 3.1.

```yaml
nodeLinker: pnpm
```

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

### Reference default catalog entries in package.json

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

Shows how to use the default catalog by specifying 'catalog:' as the version range for dependencies.

```json
{
  "dependencies": {
    "react": "catalog:",
    "lodash": "catalog:"
  }
}

```

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

### Simple Hello World Command

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

Registers a new 'hello' command that prints a message. Uses BaseCommand from @yarnpkg/cli and defines a static paths array. Run with 'yarn hello'.

```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,
      ],
    };
  }
};
```

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

### Bundle Dependencies Deprecation

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

Example of the bundleDependencies field which is no longer supported in Yarn 2.

```json
{
  "bundleDependencies": [
    "not-supported-anymore"
  ]
}
```

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

### Generate VSCode settings

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

Generates a .vscode/settings.json file for VSCode. Requires the ZipFS extension to be installed.

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

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

### Gitignore for non-Zero-Installs

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

Use this .gitignore configuration when not using Zero-Installs to ignore .pnp.* files and most .yarn contents while keeping patches, plugins, releases, sdks, and versions.

```gitignore
.pnp.*
.yarn/*
!.yarn/patches
!.yarn/plugins
!.yarn/releases
!.yarn/sdks
!.yarn/versions

```

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

### Generate CoC nvim settings

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

Generates a .vim/coc-settings.json file for CoC nvim. Requires vim-rzip to be installed.

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

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

### Generate base SDK and editor settings

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

Generates the base SDK and editor settings for the specified editors (e.g., vscode, vim).

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

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

### Incorrect code for no node module strings rule

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

Example of incorrect code that references node_modules in a require path.

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

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

### List staged packages command

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

Lists all staged package versions awaiting approval. Optionally filter by package name.

```bash
yarn npm stage list [package-name]

```

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

### Correct code for no unqualified webpack config rule

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

Example of correct code that uses require.resolve for a loader in webpack config.

```javascript
const webpackConfig = {
  use: require.resolve(`ts-loader`),
};
```

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

### Gitignore for Zero-Installs

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

Use this .gitignore configuration when using Zero-Installs to keep the cache and patches while ignoring other .yarn contents.

```gitignore
.yarn/*
!.yarn/cache
!.yarn/patches
!.yarn/plugins
!.yarn/releases
!.yarn/sdks
!.yarn/versions

```

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

### Build the Yarn CLI from the repository with yarn build:cli

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

Run this command after cloning the repository to build the Yarn CLI locally. The global `yarn` command will then immediately reflect local changes because the repository's `.yarnrc.yml` uses `yarnPath` to point to the newly built CLI. No other command is needed; dependencies are checked into the repository.

```bash
yarn build:cli
```

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

### Incorrect code for no unqualified webpack config rule

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

Example of incorrect code that references a loader as a string in webpack config.

```javascript
const webpackConfig = {
  use: `ts-loader`,
};
```

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

### Correct code for no node module strings rule

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

Example of correct code that imports a module by its name without node_modules.

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

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

### Read-Only Filesystem Error Example

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

Demonstrates the EROFS error when attempting to modify a package file within the read-only cache.

```ts
const {writeFileSync} = require(`fs`);
const lodash = require.resolve(`lodash`);

// Error: EROFS: read-only filesystem, open '/node_modules/lodash/lodash.js'
writeFileSync(lodash, `module.exports = 42;`);
```

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

### Configure supportedArchitectures in .yarnrc.yml

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

Manually restrict package architectures for optional dependencies. Useful for zero-install setups with an immutable package set.

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

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

### Using exec: protocol in package.json with gen-pkg.js

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

Configure a dependency to use the exec: protocol, pointing to a script that generates the package content. The script must write a package.json and any other files into the buildDir provided by execEnv.

```json
{
  "dependencies": {
    "pkg": "exec:./gen-pkg.js"
  }
}
```

```js
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()};\n`);
```

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

### Old peer dependency warnings

Source: https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/blog/2020-11-30-release-2.4.mdx

Example of the old peer dependency warnings that Yarn used to emit. These warnings were often redundant and not actionable.

```text
your project provides react@17 to @storybook/react, which isn't compatible with react@^15
your project provides react@17 to storybook-plugin-foo, which isn't compatible with react@^15
your project provides react@17 to storybook-plugin-bar, which isn't compatible with react@^15
```

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

### Enable node-modules linker in .yarnrc.yml

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

Add this configuration to your .yarnrc.yml file to enable the experimental node_modules installation strategy. This is required because the plugin is not enabled by default.

```yaml
nodeLinker: node-modules
```

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

### Build CLI and run integration tests

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

Run `yarn build:cli` first to prebuild the CLI, then `yarn test:integration` to run the integration tests. The CLI must be rebuilt after each modification for the integration tests to pick up changes.

```bash
yarn build:cli
```

```bash
yarn test:integration
```

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

### Enable node-modules linker for a workspace with yarn config set

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

Sets the `nodeLinker` to `node-modules` for a specific workspace, used for hybrid PnP + node_modules setups.

```bash
yarn --cwd packages/myproj config set nodeLinker node-modules
```

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

### PARSE_BARE_IDENTIFIER algorithm

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

Defines the PARSE_BARE_IDENTIFIER algorithm, which splits a bare specifier into an ident and modulePath. It handles scoped packages (starting with @) and throws an error if a scoped specifier lacks a slash separator.

```text
PARSE_BARE_IDENTIFIER(specifier)
```
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