Important: This documentation covers Yarn 2.
For 1.x docs, see classic.yarnpkg.com.
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Protocols

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Table

The following protocols can be used by any dependency entry listed in the dependencies or devDependencies fields. While they work regardless of the context we strongly recommend you to only use semver ranges on published packages as they are the one common protocol whose semantic is clearly defined across all package managers.

Name Example Description
Semver ^1.2.3 Resolves from the default registry
Tag latest Resolves from the default registry
Npm alias npm:name@... Resolves from the npm registry
Git git@github.com:foo/bar.git Downloads a public package from a Git repository
GitHub github:foo/bar Downloads a public package from GitHub
GitHub foo/bar Alias for the github: protocol
File file:./my-package Copies the target location into the cache
Link link:./my-folder Creates a link to the ./my-folder folder (ignore dependencies)
Patch patch:left-pad@1.0.0#./my-patch.patch Creates a patched copy of the original package
Portal portal:./my-folder Creates a link to the ./my-folder folder (follow dependencies)
Workspace workspace:* Creates a link to a package in another workspace
Exec exec:./my-generator-package Experimental & Plugin
Instructs Yarn to execute the specified Node script and use its output as package content

Details

Exec

This protocol is experimental, and only available after installing an optional plugin.

Its documentation and usage can be found on GitHub: yarnpkg/berry/blob/master/packages/plugin-exec/README.md.

Git

The Git protocol, while fairly old, has been significantly improved starting from Yarn 2. In particular, some things to know:

  • The target repository won't be used as-is - it will first be packed using pack

  • You can explicitly request a tag, commit, branch, or semver tag, by using one of those keywords (if you're missing the keyword, Yarn will look for the first thing that seems to match, as in prior versions):

git@github.com:yarnpkg/berry.git#tag=@yarnpkg/cli/2.2.0
git@github.com:yarnpkg/berry.git#commit=a806c88
git@github.com:yarnpkg/berry.git#head=master
  • Yarn will use either of Yarn, npm, or pnpm to pack the repository, based on the repository style (ie we'll use Yarn if there's a yarn.lock, npm if there's a package-lock.json, or pnpm if there's a pnpm-lock.yaml)

  • Workspaces can be cloned as long as the remote repository uses Yarn (we can't support pnpm because it doesn't have equivalent for the workspace command). Just reference the workspace by name in your range (you can optionally enforce the tag as well):

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

Patch

The patch: protocol is meant to be used with yarn patch and yarn patch-commit. It allows you to change the sources for a package without having to completely fork the dependency. The intended workflow is:

  1. Find a package you want to patch (let's say lodash@^1.0.0)
  2. Run yarn patch lodash
  3. Edit the folder the command generated
  4. Once you're done, run yarn patch-commit <path> > my-patch.diff
  5. In your manifest, change the dependency from ^1.0.0 to:
patch:lodash@^1.0.0#./my-patch.diff

Note that if you wish to update a transitive dependency (ie not directly yours), it's perfectly possible to use the resolutions field.

Workspace

The workspace: protocol is meant to be used with workspaces. While Yarn automatically picks workspace resolutions when they match, there are times where you absolutely don't want to risk using a package from the remote registry even if the versions don't match (for example if your project isn't actually meant to be published and you just want to use the workspaces to better compartmentalize your code).

Our current recommendation is to use workspace:*, which will almost always do what you expect. See the documentation of workspaces for full details about this protocol.

Frequently Asked Questions

Can I install a workspace of a project when using the git: protocol?

Yes! Yarn supports workspaces even through git dependencies, using the following syntax:

{
  "dependencies": {
    "my-pkg": "org/app#workspace=my-pkg"
  }
}

You can even combine it with the branch selectors:

{
  "dependencies": {
    "my-pkg": "org/app#head=next&workspace=my-pkg"
  }
}

Note: For this workflow to work, make sure that each individual workspaces can be built just by running yarn install && yarn pack into each individual workspace. In particular, avoid third-party release scripts unless they use yarn pack under the hood.

Why can't I add dependencies through the patch: protocol?

A Yarn install is split across multiple steps (described here). Most importantly, we first fully resolve the dependency tree, and only then do we download the packages from their remote sources. Since patches occur during this second step, by the time we inject the new dependencies it's already too late as the dependency tree has already been frozen.

In order to add dependencies to a package, either fork it (and reference it through the Git protocol, for example), or use the packageExtensions mechanism which is specifically made to add new runtime dependencies to packages.

Many tools support a feature generally known as "aliases", which allows you to map a specific directory to a package name. This pattern allows you to use regular package imports (my-app/Toolbar) instead of potentially complex relative paths (../../../Toolbar). It sounds awesome! So why do we recommend against this practice?

As we said, many tools support this feature. But the trick is that their implementations and configurations are all subtly different. Depending on the tool, it will be called moduleNameMapper, resolve.alias, paths, or even module.name_mapper. Depending on the tool it'll be a regex, a domain-specific language, or just a package name. All those differences make it difficult to keep the configurations synchronized, and likely that a mistake will creep in. Even worse, it'll lock you out of tools that don't support aliases, since they won't know how to deal with these paths they know nothing about.

Enter the link: protocol! Through it, you directly instruct the package manager to install a resolution from the given name to the given path. Since the package manager's knowledge base is used by every package in your project, adding a link dependency is enough to make all your tooling aware of this new connection. No need for further configuration 💫

{
  "dependencies": {
    "src": "link:./src"
  }
}

Tip: Yarn 2 implements support for self-references, making the link: protocol unneeded in most cases. Any file that's part of a package will always be able to import any file from its own package using the package name - even the top-level project! Just add a "name": "app" field into your top-level package.json, and you'll be able to use import 'app/Toolbar' without further ado.

Note: You may be tempted t alias a scope without giving an explicit name (ie "@app": "link:./src"). Don't. This pattern is invalid and won't work. The reason for this is that package identifiers have a required package name, and an optional scope name. As a result, a scope without package name is a syntax error. Prefer doing "app": "link:./src", which will still allow you to use subdirectories if needed (ie import 'app/toolbar/Icon').

Note: By reading this FAQ entry, you might think that we recommend against using aliases altogether. This isn't entirely correct. While using aliases for directory mapping is a practice we advise against, they have their usefulness in other contexts. For example, using an alias to map the fs module into a local mock is perfectly fine.

The link: protocol is meant to link a package name to a folder on the disk - any folder. For example, one perfect use case for the link: protocol is to map your src folder to a clearer name that you can then use from your Node applications without having to use relative paths (for example you could link my-app to link:./src so that you can call require('my-app') from any file within your application).

Because such destination folders typically don't contain package.json, the link: protocol doesn't even try to read them. It can cause problems when you want to link an identifier to a different package on the disk (similar to what yarn link does) because then the transitive dependencies aren't resolved.

In order to solve this use case, the new portal: protocol available in the v2 opens a portal to any package located on your disk. Because portals are meant to only target packages they can leverage the information from the package.json files listed within their targets to properly resolve transitive dependencies.