Moonrepo — Fast Monorepo Management and Build Orchestration

Introduction

Moonrepo (moon) is a monorepo management tool written in Rust that handles task running, dependency graph resolution, and project organization for repositories containing multiple projects. It is designed to be fast, language-agnostic, and to reduce the configuration overhead common in large monorepos.

What Moonrepo Does

• Orchestrates task execution across multiple projects with automatic dependency ordering
• Detects affected projects from Git changes and only runs necessary tasks
• Manages toolchain versions for Node.js, Bun, Deno, and Rust automatically
• Generates project configuration from templates using a code generation system
• Enforces project boundaries and dependency constraints through ownership rules

Architecture Overview

Moon reads a .moon/workspace.yml configuration that defines the workspace structure and toolchain settings. Each project contains a moon.yml declaring its tasks and dependencies. When a task is run, moon builds a directed acyclic graph of all task and project dependencies, hashes inputs for cache keys, and executes tasks in parallel where possible. Outputs are cached locally and can be shared via a remote cache for CI acceleration.

Self-Hosting & Configuration

• Install the moon binary via the install script, npm, or Homebrew
• Run moon init to create .moon/workspace.yml and configure project sources
• Define tasks in each project's moon.yml with commands, inputs, outputs, and dependencies
• Set up toolchain auto-management in .moon/toolchain.yml to pin Node.js or Rust versions
• Enable remote caching by configuring a moonbase or S3-compatible storage endpoint

Key Features

• Rust-based CLI with sub-second startup and parallel task execution
• Smart affected detection using Git diff to skip unchanged projects in CI
• Integrated toolchain management that downloads and pins language runtime versions
• Code ownership system with CODEOWNERS-like rules for enforcing project boundaries
• VCS hooks management for running linters and formatters on pre-commit

Comparison with Similar Tools

• Turborepo — JavaScript/TypeScript focused; Moon is language-agnostic and manages toolchains
• Nx — Plugin-rich with deep framework integration; Moon is simpler and configuration-driven
• Bazel — Hermetic builds for massive repos; Moon is easier to adopt with less configuration
• Lerna — npm package publishing tool; Moon handles task orchestration and project constraints
• Rush — Microsoft monorepo manager for npm; Moon supports multiple language runtimes

FAQ

Q: What languages does Moon support? A: Moon is language-agnostic for task running. Toolchain management currently covers Node.js, Bun, Deno, and Rust with more planned.

Q: How does caching work? A: Moon hashes task inputs (source files, env vars, dependencies) to create cache keys. Matching hashes skip execution and restore cached outputs.

Q: Can I migrate from Turborepo or Nx? A: Yes. Moon provides migration guides. The task configuration format is different but conceptually similar, and moon can coexist during migration.

Q: Does it work with Docker? A: Yes. Moon can run inside Docker containers and supports generating Dockerfiles that leverage the dependency graph for optimal layer caching.

Sources

• https://github.com/moonrepo/moon
• https://moonrepo.dev/