Understanding Duplicate Dependencies in Nx Monorepos

When using Nx to manage monorepos, dependencies should be properly deduplicated to ensure consistency across projects. However, factors like multiple package managers (npm, yarn, pnpm), incorrect peer dependencies, or misconfigured root package.json can lead to duplicate versions of the same package being installed.

Common Causes of Duplicate Dependencies

• Multiple versions of a package: Different projects in the monorepo require different versions of the same dependency.
• Incorrect peer dependencies: A package has peer dependencies that are not properly aligned.
• Improper package hoisting: Dependencies get installed at different levels due to npm/yarn/pnpm behavior.
• Using workspaces incorrectly: Improper workspace configurations lead to duplicate installs.

Diagnosing Duplicate Dependencies

Using Nx Dependency Graph

Nx provides a built-in dependency graph to visualize dependencies:

nx graph

This command generates a visual representation of dependencies, helping identify multiple versions of the same package.

Checking Installed Versions

Run the following to identify duplicate versions:

npm ls package-name

For yarn:

yarn list package-name

For pnpm:

pnpm list package-name

Using Deduplicate Tools

For npm:

npx npm-deduplicate

For yarn:

yarn deduplicate

Fixing Duplicate Dependencies

Aligning Dependency Versions

Ensure all projects within the monorepo use the same version of dependencies by updating package.json:

"dependencies": {
  "react": "18.2.0"
}

Configuring Nx Implicit Dependencies

Define dependencies explicitly in nx.json:

{
  "implicitDependencies": {
    "libs/shared": ["apps/app1", "apps/app2"]
  }
}

Using Yarn or Pnpm Workspaces

Enable workspace mode for better dependency management:

{
  "workspaces": ["apps/*", "libs/*"]
}

Enforcing Hoisting

For pnpm, enforce hoisting by enabling shared dependencies:

pnpm install --shamefully-hoist

Preventing Future Dependency Issues

• Use Nx plugin @nrwl/workspace for automatic dependency validation.
• Regularly check and align package versions across the monorepo.
• Utilize automated CI/CD checks to prevent dependency mismatches.

Conclusion

Duplicate dependencies in an Nx monorepo can cause severe issues, but using proper dependency management techniques and tools like Nx graph, workspaces, and deduplication commands, teams can maintain a stable and optimized monorepo setup.

FAQs

1. Why do I see multiple versions of the same package in my Nx monorepo?

This happens when different projects declare different versions, leading to multiple installations.

2. Can pnpm help reduce duplicate dependencies?

Yes, pnpm enforces a shared dependency model, reducing unnecessary duplicate versions.

3. What is the best way to ensure dependency consistency?

Use workspace tools like Yarn or Pnpm, and keep all projects aligned with the same dependency versions.

4. How can I visualize dependency issues in Nx?

Run nx graph to generate a visual representation of the dependency tree.

5. Should I always enable package hoisting?

It depends on your setup. Hoisting can improve performance but might cause version conflicts if not managed properly.