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From Yarn to Pnpm

Yarn and Pnpm are both package managers.

Why?​

In order to choose between these two alternatives, we have checked the following criteria:

  • popularity: this is the package manager that is used by all the major frameworks (NextJS, VueJS, Vite, etc.)
  • performance : pnpm uses hardlinks for node_modules by default, so you won't end up with 100GB of node_modules across the projects on your machine. This also makes performance way better for installation, update, etc.
  • stability: the way pnpm handles workspaces (monorepo) and node_modules in each package is much better than yarn: you have a node_modules folder in all your packages, rather than everything in the root. The impact is that if you have a dependency that does something crazy (like Serverless that dynamically requires modules), it will work

For more context, check out the migration PR.

How?​

Migrating from yarn to pnpm is quite straightforward:

  • install pnpm npm install -g pnpm

  • rename all your yarn commands to pnpm:

    • yarn -> pnpm install
    • yarn test -> pnpm test
    • yarn package -> pnpm package
    • yarn deploy -> pnpm run deploy (run is required here, as pnpm deploy is a reserved command)

  • replace all occurrences of the string yarn.lock in your source files with pnpm-lock.yaml (search, prettier, etc.)

  • in your CI/CD, when using actions/setup-node@v3, set cache to 'pnpm'

  • if you're using yarn PnP, remove .yarnrc.yml and the .yarn folder

  • in the root package.json set the packageManager key to pnpm@<version> (replace <version> with the latest available version)

  • create a pnpm-workspace.yaml file with:

    packages:
      - 'services/*'
      - 'contracts/*'
      - 'packages/*'

    and everything that is in the workspaces key of the root package.json

  • run pnpm import to generate a pnpm-lock.yaml from your yarn.lock, then remove yarn.lock

  • run pnpm install

Troubleshooting​

Pnpm is more strict than Yarn when dealing with dependencies. This is a good thing, because it makes package configurations self-sufficient.

However, migrating from yarn to pnpm, you may find that you miss some dependencies in your packages for this reason. In this case:

  • add the missing types packages for obvious ones
  • dig into dependencies to find out source issues in less obvious ones

Most often it should be an issue with peer dependencies that are not properly satisfied.