Upgrading to Yarn 4

My experiences upgrading from Yarn 3 to Yarn 4 in a large codebase.

Upgrading to Yarn 4

I maintain a set of templates and a starter project builder for fullstack projects: Goldstack. This project makes heavy use of Yarn 3 features, specifically for workspace management.

I realised that a new version of Yarn, Yarn 4 was released recently, so I wanted to explore if I can easily update this project from Yarn 3 to Yarn 4.

This project contains more than 70 workspaces (including sub-workspaces) and uses a number of frameworks and libraries, such as:

  • TypeScript
  • React
  • Next.js
  • ESLint
  • and many more

So I think it can be a good testing ground for upgrading to Yarn 4.

I completed the upgrade and released this in version 0.5.0 of Goldstack.

Overall it took me around 3 hours to perform the upgrade. Here an overview of what I needed to do:

Updating Yarn

First, Yarn needed to be updated to version 4 using the following commands:

yarn set version stable
yarn install

Note that this may upgrade to a later version than Yarn 4 if you run this at a future point in time.

Upgrading Node version

Yarn 4 is not compatible with earlier versions of Node. Specifically Node 16 is no longer supported.

I needed to ensure that all GitHub actions provide an environment that runs in Node 18:

      - uses: actions/checkout@v2
      - uses: actions/setup-node@v2
          node-version: '18'

Fixing CLI commands

There was an incompatible change included in Yarn 4 with respect to the foreach command. Previously it was possible to run a command as follows:

yarn foreach run clean

However, now Yarn requires to add a qualifier. Specifically one of the following:

Command Description
-A,--all Run the command on all workspaces of a project
-R,--recursive Run the command on the current workspace and all of its recursive dependencies
-W,--worktree Run the command on all workspaces of the current worktree

I provided the -W or --worktree option for all occurrences where I previously used foreach. I usually just wanted to run a command for all packages for a workspace - but not including recursive dependencies or all packages in the whole project (what -A will do).

A worktree is defined in the Yarn documentation as:

[...] a worktree is the name given to workspaces that list their own child workspaces.

I would say overall it was a fairly easy process to upgrade to Yarn 4. Next from here I would like to explore:

  • Yarn now supports having its binary managed through corepack. My template currently still uses yarnPath.
  • Yarn supports a hybrid mode that allows managing package dependencies using Yarn Plug'n'play and the 'node linker' (that requires the node_modules) folder alongside each other. I want to explore whether this can be used to create a mobile template based on Expo