Mastering Monorepo Builds: Translating pnpm Commands to npm

Managing a monorepo can be both exciting and challenging. Tools like pnpm make it easy to handle tasks like building all packages in a monorepo in parallel with filters. However, if you're using npm and want to replicate a pnpm workflow such as pnpm --parallel --filter "./**" build, you’ll need to adapt and understand a few nuances. This article will guide you through creating an equivalent npm command, highlight the key differences between npm and pnpm, and cover additional considerations for efficient monorepo management.

Breaking Down the Command

The pnpm command:

pnpm --parallel --filter "./**" build

What it does:

1. --parallel: Runs the build script in all matched packages simultaneously.
2. --filter "./**": Filters the packages to include everything in the monorepo.
3. build: Refers to the build script defined in the package.json of each package.

With npm, you can achieve a similar result using workspaces and some adjustments.

The Equivalent npm Command

For a native npm workspace setup, the closest equivalent command is:

npm run build --workspaces --if-present

Explanation:

1. --workspaces: This ensures the command is executed in all workspace packages.
2. --if-present: Prevents errors for packages that don't have a build script. This is especially useful for monorepos where not all packages need a build step.

However, npm does not natively support parallel execution. By default, it processes scripts sequentially. This is a key difference from pnpm.

Adding Parallel Execution

To truly run npm scripts in parallel, you’ll need a tool like concurrently. Here’s how you can do it:

1. Install concurrently:

npm install -g concurrently

2. Run builds in parallel:

concurrently "npm run build -w package1" "npm run build -w package2"

If you want to dynamically include all workspaces, consider writing a small script to automate this.

Key Considerations for Monorepo Builds

1. Understand Workspace Scripts

• In a monorepo, npm treats workspaces as first-class citizens.
• Make sure your package.json has a workspaces field, like this:

{
  "workspaces": ["packages/*"]
}

Efficient Dependency Management

• pnpm is more space-efficient for managing dependencies, thanks to its content-addressable store.
• If you're using npm, be aware that duplicate dependencies across packages might take up unnecessary space.

3. Add Missing Filters

If you need to include or exclude specific packages, you’ll need to implement filtering manually with npm. For example:

• Only include packages with a certain name:

npm run build --workspace=package-name

• Exclude certain packages by modifying your script logic or workspace definitions.

4. Error Handling

pnpm provides better error isolation. If one package fails, the others can still proceed. For npm, you may need to add error handling logic, especially when using parallel tools like concurrently.

Why Consider pnpm for Monorepos?

If you're struggling to replicate pnpm features with npm, it might be worth reconsidering your toolchain. Here are a few reasons:

• Speed: pnpm is faster for many operations, especially in large monorepos.
• Efficiency: It avoids duplicate node_modules installations.
• Built-in Filtering: Features like --filter are powerful for managing specific tasks.

Finally

While you can replicate most pnpm workflows with npm, the process often requires additional tools or scripts. The equivalent npm command for pnpm --parallel --filter "./**" build is:

npm run build --workspaces --if-present

However, for parallel execution, you’ll need tools like concurrently.

If your monorepo’s complexity grows, you might find that pnpm provides a more intuitive and performant workflow. Regardless of your tool of choice, understanding the nuances of each system will help you create a scalable and maintainable build process for your monorepo.

Support Us