Monorepoの構造とレイアウト

Welcome! In a monorepo, many projects live together in one place. A clear, thoughtful structure is super important for keeping things organized.

It helps developers quickly find what they need, promotes code sharing, and makes managing the entire codebase much easier as it grows.

At the very top level of your monorepo, the root directory, you'll find files that apply to the entire repository. Think of them as global settings.

• .git/: Git's internal tracking files.
• .gitignore: Tells Git which files to ignore.
• README.md: The main description of your monorepo.
• package.json: (If using Node.js) Monorepo-level scripts or dependencies.
• tools/: Global utility scripts.

To keep things tidy, projects are usually grouped into top-level directories based on their type or purpose. The most common ones are apps/ and packages/ (sometimes libs/).

• apps/: For deployable applications like web apps, mobile apps, or API services.
• packages/ (or libs/): For reusable libraries, components, or shared utilities that multiple apps might use.

This clear separation helps you understand a project's role at a glance.

Each folder within apps/ represents a distinct, standalone application. They usually have their own source code, configuration, and dependencies.

monorepo/
├── apps/
│   ├── web-app/         # Your frontend application
│   │   ├── src/
│   │   └── package.json
│   ├── api-service/     # Your backend API
│   │   ├── src/
│   │   └── Dockerfile
│   └── mobile-app/      # Your mobile application
│       ├── src/
│       └── ...
└── ...

This structure keeps each application isolated while being part of the larger monorepo.

The packages/ (or libs/) directory is where you put all your reusable code. These are often smaller, focused libraries or UI components that can be shared across multiple applications.

monorepo/
├── packages/
│   ├── ui-components/   # Reusable UI library
│   │   ├── src/
│   │   └── package.json
│   ├── shared-utils/    # Common utility functions
│   │   └── src/
│   └── auth-lib/        # Authentication logic
│       └── src/
└── ...

This promotes code reuse and consistency across your projects.

To ensure consistency, many monorepos centralize configuration files for tools like linters (for code style), formatters (for code layout), and build systems.

monorepo/
├── .eslintrc.js       # Linter configuration
├── prettier.config.js # Code formatter configuration
├── jest.config.js     # Test runner configuration
├── tsconfig.base.json # Base TypeScript config
└── ...

These files often live at the root or in a dedicated config/ folder, applying rules consistently to all projects.

A well-defined monorepo structure offers significant advantages:

• Discoverability: New team members can quickly understand where everything is.
• Consistency: Enforces uniform project layouts and coding standards effortlessly.
• Maintainability: Makes refactoring and managing dependencies much simpler.
• Tooling: Streamlines setup for monorepo-aware build and development tools.

It's an investment that pays off in the long run!

While monorepo structure is about organizing files and folders, here's a basic Java program to demonstrate how runnable code appears in CoddyKit. This helps you get comfortable with the editor!

Clear and consistent naming is crucial in a monorepo. It helps avoid confusion and makes the codebase more readable.

• Kebab-case: Use kebab-case for project and folder names (e.g., web-app, shared-utils).
• Specific names: Avoid generic names like utils; be more specific (e.g., date-utils, api-client).
• Prefixes: For larger organizations, consider prefixing shared packages (e.g., @myorg/ui-components).

Consider a monorepo containing a web application, an API service, and a shared UI component library. What are common and effective ways to organize these projects?

Fantastic work! Today, we learned the importance of structuring a monorepo. We covered organizing applications into apps/, shared libraries into packages/ (or libs/), and centralizing global configurations.

A well-defined layout makes your monorepo easier to navigate, more consistent, and simpler to maintain. Next, we'll dive into specific tools that help manage these complex structures!