Building a Monorepo with Yarn 2

Summary

The post presents Yarn 2 workspaces as a way to manage dependencies for a JavaScript or Node.js monorepo containing separate server and UI applications. It configures the root package.json with workspace directories, imports the workspace-tools plugin, pins the project to a checked-in Yarn binary with yarn set version berry, and enables the dependency cache through .yarn/cache and Plug’n’Play. The walkthrough adds Express, TypeScript, and @types/express to a server workspace, creates a Next.js UI workspace, and uses workspace scripts to build both applications, while yarn dlx initializes TypeScript without a global install. It also shows the Git files to retain, generated JavaScript to ignore, and a Heroku start script that launches the server workspace; the stated benefit is faster installs through a committed cache and zero-install deployment.

Takeaways

1. 1

   The root package.json lists the server and ui directories under workspaces, while the workspace-tools plugin enables commands such as yarn workspaces foreach run build.

2. 2

   Yarn 2 creates .pnp.js, .yarn/cache, and yarn.lock; .pnp.js tells the Node app or build how to locate dependencies stored in the cache.

3. 3

   Heroku uses the root package.json start script to start the web process, with the example delegating startup to the server workspace.