Start using Yarn v2 codename berry today

If you're using yarn version 1 already for your dependencies installations you might consider to migrate your project client dependencies installation to the Yarn v2.

Yarn 2 (codename berry) is still under active development which results in poor documentation and lack of exact instructions. Yarn v1 is not in an active developing anymore and it's clear that we need to migrate to the v2 in the near future.

Start using Yarn 2 today

You can find initial instructions on the Yarn 2 official installation page. They are working on a new documentation portal under https://next.yarnpkg.com/.

Set yarn version to the v2 executing in your project folder:

yarn policies set-version v2

Verify that yarn version was switched to the v2

yarn --version
v2.0.0

Working with private NPM packages

If you use any private packages in your project consider the following options:

yarn npm login --scope npm_org_scope

Check under which user you are currently logged in

yarn npm whoami

Yarn generated files purpose and their meaning

Yarn 2 generates the following new files:

.yarn - (folder): keeps your modules in a zip file, you want to keep this in git
pnp.js - helps tools to understand where modules are
yarnrc.yml - the config for yarn v2 (write using YML)
.yarnrc - the config for yarn v1 to tell it to use v2

Yarn versions

To list all the versions of Yarn you have installed

brew list --versions yarn

How to set Yarn version back to the "old" version

To roll back, from the home ~ directory remove .yarn folder with the berry release that will make it possible to use your yarn installed with brew.

cd ~
rm -rf .yarn/

Failures

Keep in mind that Yarn v2 is in a kind of "beta" state so failures and bugs are likely to occur. I myself experience errors when using Yarn v2 while installing private npm packages from the GitHub Package Registry.

How successful install with Yarn 2 looks like

Let's use Create React App CLI tool to generate an example project and then install modules with Yarn 2. To do so step-by-step execute from a terminal:

yarn create react-app my-app
cd my-app
yarn start # app running on http://localhost:3000/
rm -rf node_modules # remove dependencies(node_modules) installed with yarn v1
yarn policies set-version v2 # use yarn v2
yarn install # install dependencies using yarn v2
yarn start # app is running on http://localhost:3000/ with deps installed with Yarn 2

Successful installation

Yarn 2 FAQ

Should I delete node_modules folder?

Yes. Remove your node_modules with rm -rf */node_modules (or whatever it takes to recursively delete).

Yup - we print a warning during linking if we notice that there's a lingering node_modules. The warning error code points to here, which I should edit to include a command to remove them in one go!

Should I delete my yarn.lock file?

Nope - Yarn will automatically migrate the lockfile and reuse the versions that are already stored inside. We'll still need to make network requests to retrieve the necessary information that weren't part of the v1 format, but apart from that keeping the lockfile is advised.

What is stored inside `.yarn/cache` folder?

All the downloaded dependencies (modules) in the .zip format.

ls .yarn/cache

Conclusion

You can start using and experiment with yarn v2 today, no need to wait for its official release. It's quite stable already, it was re-written on TypeScript to leverage type system. Have some fun and hopefully it works for your project 🙂🙏🏻