monorepo eslint check if import exists in workspace dependecies

3 min read 22-01-2025

monorepo eslint check if import exists in workspace dependecies

Managing dependencies in a monorepo can be tricky. One common challenge is ensuring that all imports within your project correctly reference existing packages within your workspace. This article details how to configure ESLint to verify that all your imports point to valid dependencies within your monorepo. This helps prevent runtime errors and maintain a cleaner, more reliable codebase.

Why Check Imports in a Monorepo?

Using a monorepo offers many advantages, including streamlined dependency management and easier code sharing. However, the flexibility of importing packages from within the workspace also introduces potential issues. If you refactor or remove a package, or if a typo slips into an import statement, your build might fail silently, or even worse, produce unexpected behavior in production.

By configuring ESLint to validate imports within your monorepo, you gain:

Early Error Detection: Catch import errors during development, preventing costly debugging later.
Improved Code Maintainability: Enforce consistency in how packages are referenced within the workspace.
Reduced Runtime Errors: Prevent runtime exceptions caused by incorrect or missing imports.
Enhanced Code Reliability: Increase the overall stability and predictability of your application.

Setting up ESLint for Monorepo Import Checking

The key to achieving this lies in using ESLint plugins and rules that understand your monorepo's structure. We'll focus on leveraging the power of eslint-plugin-import and potentially eslint-plugin-workspace. The specific setup will depend on your monorepo's structure (e.g., Yarn Workspaces, npm Workspaces, Lerna, Turborepo).

1. Install Necessary Packages

First, install the required ESLint plugins:

npm install --save-dev eslint-plugin-import eslint-plugin-workspace
# or
yarn add --dev eslint-plugin-import eslint-plugin-workspace

eslint-plugin-import provides general import validation, while eslint-plugin-workspace specifically targets monorepo structures. Note that eslint-plugin-workspace may require additional configuration depending on your monorepo manager.

2. Configure ESLint

Next, configure your ESLint .eslintrc.js (or similar) file. This is where you'll specify the rules and potentially define your workspace's package locations.

Here’s an example configuration leveraging both plugins:

module.exports = {
  // ... other ESLint configurations ...
  plugins: ['import', 'workspace'],
  rules: {
    'import/no-unresolved': 'error', // Enforces that all imports can be resolved
    'workspace/import-from-workspace': ['error', {
      // Configure paths to your workspace packages 
      // Adjust this based on your monorepo setup
      packages: ['packages/*', 'libs/*'],
    }],
  },
  settings: {
    'import/resolver': {
      'node': {
        extensions: ['.js', '.jsx', '.ts', '.tsx'],
      },
      'workspace': {
          // This setting can vary widely depending on your setup
          // For Turborepo and Nx, it's usually not necessary
          // For other monorepo tools, consult their documentation
      },
    },
  },
};

Crucial Configuration Notes:

The 'import/no-unresolved' rule from eslint-plugin-import is essential. It flags imports that cannot be resolved by Node.js.
The 'workspace/import-from-workspace' rule from eslint-plugin-workspace specifically checks if imports come from your defined workspace packages. You must adjust the packages array to match the directory structure of your monorepo where your packages reside. Incorrect configuration here will lead to false positives.
The import/resolver section is critical for ESLint to correctly understand your project's structure and find the packages within your monorepo. The 'node' resolver handles typical Node.js imports. The 'workspace' resolver needs careful adjustment based on the tool used to manage your monorepo (e.g., Yarn, npm, Lerna, Turborepo). Consult the documentation for your monorepo tool for detailed configuration.

3. Running ESLint

After configuring ESLint, run it against your codebase. ESLint will now highlight any import statements that violate the rules you've defined.

npx eslint .  //Or your preferred ESLint command

Handling Different Monorepo Structures

The exact configuration will vary depending on your chosen monorepo management tool. For instance:

Yarn Workspaces/npm Workspaces: You'll likely need to carefully configure the 'workspace' resolver in the ESLint settings to accurately map your package locations. The packages array in the workspace/import-from-workspace rule should reflect your workspace's package layout.
Lerna/Turborepo/Nx: These tools often have their own integration mechanisms with ESLint. Consult their respective documentation for best practices and how to correctly configure the ESLint plugins.

Conclusion

By implementing these steps, you drastically improve the reliability and maintainability of your monorepo. Regularly running ESLint with these configurations will catch potential issues early in your development cycle, saving you time and effort in the long run. Remember to carefully configure the packages array and the import/resolver section to align precisely with your monorepo's structure. This ensures accuracy and prevents false positives from interfering with your development workflow.