How Do I Enforce Strict Peer Dependencies At PR Time?

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Introduction

As a developer working on a large-scale npm-based monorepo with hundreds of contributors, managing dependencies can be a daunting task. One of the key challenges is ensuring that all dependencies are properly declared and versioned in each project's package.json file. In this article, we will explore the concept of strict peer dependencies and provide a step-by-step guide on how to enforce them at pull request (PR) time using Node.js and npm.

What are Peer Dependencies?

Peer dependencies are dependencies that are required by a package but are not installed by npm by default. They are typically specified in the peerDependencies field of a package's package.json file. Peer dependencies are used to ensure that a package is used with compatible versions of other packages.

Why Enforce Strict Peer Dependencies?

Enforcing strict peer dependencies can help prevent a range of issues, including:

  • Version conflicts: When multiple packages have different versions of the same peer dependency, it can lead to version conflicts and errors.
  • Incompatible dependencies: When a package is used with an incompatible version of a peer dependency, it can cause errors and crashes.
  • Security vulnerabilities: When a package is used with an outdated version of a peer dependency, it can expose the application to security vulnerabilities.

How to Enforce Strict Peer Dependencies at PR Time

To enforce strict peer dependencies at PR time, you can use a combination of npm scripts, linters, and CI/CD tools. Here's a step-by-step guide:

1. Configure Peer Dependencies in package.json

First, you need to configure peer dependencies in your project's package.json file. Add a peerDependencies field to specify the peer dependencies required by your package.

{
  "name": "my-package",
  "version": "1.0.0",
  "peerDependencies": {
    "react": "^17.0.2",
    "react-dom": "^17.0.2"
  }
}

2. Create an npm Script to Check Peer Dependencies

Create an npm script to check peer dependencies at PR time. You can use the npm ls command to check if the peer dependencies are installed.

"scripts": {
  "check-peer-deps": "npm ls --peer --json"
}

3. Use a Linter to Enforce Peer Dependency Rules

Use a linter like npm-check to enforce peer dependency rules. You can add a lint script to your package.json file to run the linter.

"scripts": {
  "lint": "npm-check"
}

4. Configure CI/CD to Run Peer Dependency Checks

Configure your CI/CD pipeline to run the peer dependency checks at PR time. You can use tools like GitHub Actions, CircleCI, or Jenkins to automate the process.

Example GitHub Actions Workflow

name: Peer Dependency Checks

on:
pull_request:
branches:
- main


jobs:
peer-dep-checks:
runs-on: ubuntu-latest
steps:
- name: Checkout code
uses: actions/checkout@v2
- name: Install dependencies
run: npm install
- name: Run peer dependency checks
run: npm run check-peer-deps
- name: Lint code
run: npm run lint

Conclusion

Enforcing strict peer dependencies at PR time is crucial for maintaining a healthy and secure npm-based monorepo. By following the steps outlined in this article, you can ensure that all dependencies are properly declared and versioned in each project's package.json file. Remember to configure peer dependencies in package.json, create an npm script to check peer dependencies, use a linter to enforce peer dependency rules, and configure CI/CD to run peer dependency checks at PR time.

Best Practices

Here are some best practices to keep in mind when enforcing strict peer dependencies:

  • Use a consistent versioning scheme: Use a consistent versioning scheme for all dependencies to avoid version conflicts.
  • Specify peer dependencies explicitly: Specify peer dependencies explicitly in package.json to avoid implicit dependencies.
  • Use a linter: Use a linter like npm-check to enforce peer dependency rules and catch errors early.
  • Configure CI/CD: Configure your CI/CD pipeline to run peer dependency checks at PR time to catch errors early.

Q: What are the benefits of enforcing strict peer dependencies?

A: Enforcing strict peer dependencies can help prevent version conflicts, incompatible dependencies, and security vulnerabilities. It ensures that all dependencies are properly declared and versioned in each project's package.json file.

Q: How do I configure peer dependencies in package.json?

A: To configure peer dependencies in package.json, add a peerDependencies field to specify the peer dependencies required by your package. For example:

{
  "name": "my-package",
  "version": "1.0.0",
  "peerDependencies": {
    "react": "^17.0.2",
    "react-dom": "^17.0.2"
  }
}

Q: What is the difference between dependencies and peerDependencies?

A: dependencies are dependencies that are installed by npm by default, while peerDependencies are dependencies that are required by a package but are not installed by npm by default.

Q: How do I create an npm script to check peer dependencies?

A: To create an npm script to check peer dependencies, add a check-peer-deps script to your package.json file. For example:

"scripts": {
  "check-peer-deps": "npm ls --peer --json"
}

Q: What is the purpose of the npm-check linter?

A: The npm-check linter is used to enforce peer dependency rules and catch errors early. It checks if the peer dependencies are installed and if they are compatible with the package.

Q: How do I configure CI/CD to run peer dependency checks at PR time?

A: To configure CI/CD to run peer dependency checks at PR time, you can use tools like GitHub Actions, CircleCI, or Jenkins. For example, you can add a GitHub Actions workflow to run the peer dependency checks at PR time:

name: Peer Dependency Checks

on:
pull_request:
branches:
- main


jobs:
peer-dep-checks:
runs-on: ubuntu-latest
steps:
- name: Checkout code
uses: actions/checkout@v2
- name: Install dependencies
run: npm install
- name: Run peer dependency checks
run: npm run check-peer-deps
- name: Lint code
run: npm run lint

Q: What are some best practices for enforcing strict peer dependencies?

A: Some best practices for enforcing strict peer dependencies include:

  • Using a consistent versioning scheme for all dependencies
  • Specifying peer dependencies explicitly in package.json
  • Using a linter like npm-check to enforce peer dependency rules
  • Configuring CI/CD to run peer dependency checks at PR time

Q: Can I use other tools to enforce peer dependencies?

A: Yes, you can use other tools to enforce peer dependencies, such as npm-audit or yarn audit. However, npm-check is a popular and widely-used tool for enforcing peer dependencies.

Q: How do I troubleshoot peer dependency issues?

A: To troubleshoot peer dependency issues, you can use tools like npm ls or npm audit to identify the issues. You can also use a linter like npm-check to catch errors early and prevent issues from arising.

Conclusion

Enforcing strict peer dependencies at PR time is crucial for maintaining a healthy and secure npm-based monorepo. By following the best practices outlined in this article, you can ensure that all dependencies are properly declared and versioned in each project's package.json file. Remember to configure peer dependencies in package.json, create an npm script to check peer dependencies, use a linter to enforce peer dependency rules, and configure CI/CD to run peer dependency checks at PR time.