moon - Polyglot Monorepo Build System Skill

moon - Polyglot Monorepo Build System

moon is a Rust-based repository management, task orchestration, and build system for polyglot monorepos. It provides smart caching, dependency-aware task execution, and unified toolchain management.

moon v2 is now available. Run moon migrate v2 to migrate. See references/v2-migration.md for breaking changes.

When to Use moon

Managing monorepos with multiple projects/packages
Orchestrating tasks across projects with dependencies
Caching build outputs for faster CI/local builds
Managing toolchain versions (Node.js, Rust, Python, Go, etc.)
Generating project and action graphs

Quick Reference

Core Commands

moon run <target>          # Run task(s)
moon run :lint             # Run in all projects
moon run '#tag:test'       # Run by tag
moon ci                    # CI-optimized execution
moon check --all           # Run all build/test tasks
moon query projects        # List projects
moon project-graph         # Visualize dependencies

Target Syntax

| Pattern | Description | | -------------- | ------------------------------- | | project:task | Specific project and task | | :task | All projects with this task | | #tag:task | Projects with tag | | ^:task | Upstream dependencies (in deps) | | ~:task | Current project (in configs) |

Configuration Files

| File | Purpose | | ---------------------- | ---------------------------------------- | | .moon/workspace.yml | Workspace settings, project discovery | | .moon/toolchains.yml | Language versions, package managers (v2) | | .moon/tasks/*.yml | Global inherited tasks (v2) | | moon.yml | Project-level config and tasks |

v2 Note: .moon/toolchain.yml → .moon/toolchains.yml (plural), .moon/tasks.yml → .moon/tasks/*.yml

Workspace Configuration

# .moon/workspace.yml
$schema: "https://moonrepo.dev/schemas/workspace.json"

projects:
  - "apps/*"
  - "packages/*"

vcs:
  client: "git"
  defaultBranch: "main"

pipeline:
  archivableTargets:
    - ":build"
  cacheLifetime: "7 days"

Project Configuration

# moon.yml
$schema: "https://moonrepo.dev/schemas/project.json"

language: "typescript"
layer: "application" # v2: 'type' renamed to 'layer'
stack: "frontend"
tags: ["react", "graphql"]

dependsOn:
  - "shared-utils"
  - id: "api-client"
    scope: "production"

fileGroups:
  sources:
    - "src/**/*"
  tests:
    - "tests/**/*"

tasks:
  build:
    command: "vite build"
    inputs:
      - "@group(sources)"
    outputs:
      - "dist"
    deps:
      - "^:build"

  dev:
    command: "vite dev"
    preset: "server"

  # v2: Use 'script' for shell features (pipes, redirects)
  lint:
    script: "eslint . && prettier --check ."

  test:
    command: "vitest run"
    inputs:
      - "@group(sources)"
      - "@group(tests)"

Layer Types (v2)

| Layer | Description | | --------------- | --------------------- | | application | Apps, services | | library | Shareable code | | tool | CLIs, scripts | | automation | E2E/integration tests | | scaffolding | Templates, generators | | configuration | Infra, config |

Task Configuration

Task Fields

| Field | Description | | --------- | ------------------------------------ | | command | Command to execute (string or array) | | args | Additional arguments | | deps | Task dependencies | | inputs | Files for cache hashing | | outputs | Files to cache | | env | Environment variables | | extends | Inherit from another task | | preset | server or utility |

Task Inheritance

Tasks can be inherited globally via .moon/tasks/*.yml:

# .moon/tasks/node.yml
inheritedBy:
  toolchains: ["javascript", "typescript"]

fileGroups:
  sources: ["src/**/*"]

tasks:
  lint:
    command: "eslint ."
    inputs: ["@group(sources)"]

Projects control inheritance:

# moon.yml
workspace:
  inheritedTasks:
    include: ["lint", "test"]
    exclude: ["deploy"]
    rename:
      buildApp: "build"

Task Options

tasks:
  example:
    command: "cmd"
    options:
      cache: true # Enable caching
      runInCI: "affected" # affected, always, only, false
      persistent: true # Long-running process
      retryCount: 2 # Retry on failure
      timeout: 300 # Seconds
      mutex: "resource" # Exclusive lock
      priority: "high" # critical, high, normal, low

Input Tokens

inputs:
  - "@group(sources)" # File group
  - "@globs(tests)" # Glob patterns
  - "/tsconfig.base.json" # Workspace root file
  - "$NODE_ENV" # Environment variable

Toolchain Configuration

# .moon/toolchains.yml (v2: plural)
$schema: "https://moonrepo.dev/schemas/toolchains.json"

# JavaScript ecosystem (v2: required for node/bun/deno)
javascript:
  packageManager: "pnpm"
  inferTasksFromScripts: false

node:
  version: "20.10.0"

pnpm:
  version: "8.12.0"

# Alternative runtimes
bun:
  version: "1.0.0"

deno:
  version: "1.40.0"

typescript:
  syncProjectReferences: true
  routeOutDirToCache: true

rust:
  version: "1.75.0"
  bins: ["cargo-nextest", "cargo-llvm-cov"]

go:
  version: "1.21.0"

python:
  version: "3.12.0"

Toolchain Tiers

| Tier | Description | Examples | | ---- | ---------------------- | ------------------------------------ | | 3 | Full management | Node.js, Bun, Deno, Rust, Go, Python | | 2 | Ecosystem integration | PHP, Ruby | | 1 | Project categorization | Bash, Batch | | 0 | System execution | Custom tools |

CI Integration

# GitHub Actions
- uses: actions/checkout@v4
  with:
    fetch-depth: 0 # Required for affected detection

- uses: moonrepo/setup-toolchain@v0
  with:
    auto-install: true

- run: moon ci :build :test

- uses: moonrepo/run-report-action@v1
  if: success() || failure()
  with:
    access-token: ${{ secrets.GITHUB_TOKEN }}

Parallelization with Matrix

strategy:
  matrix:
    shard: [0, 1, 2, 3]

steps:
  - run: moon ci --job ${{ matrix.shard }} --job-total 4

Affected Detection

moon run :test --affected             # Only affected projects
moon run :lint --affected --status staged  # Only staged files
moon ci :test --base origin/main      # Compare against base
moon query changed-files              # v2: renamed from touched-files

Docker Support

moon docker scaffold <project>     # Generate Docker layers
moon docker setup                  # Install toolchain in Docker
moon docker prune                  # Prune for production
moon docker file <project>         # Generate Dockerfile

Moon Query Language (MQL)

# Filter projects
moon query projects "language=typescript && projectType=library"
moon run :build --query "tag=react"

# Operators: =, !=, ~, !~, &&, ||
# Fields: project, language, stack, tag, task, taskType

Additional Resources

For detailed configuration options, consult:

references/workspace-config.md - Complete workspace.yml reference
references/task-config.md - Task configuration and inheritance patterns
references/v2-migration.md - v1 to v2 migration guide
references/cli-reference.md - Full CLI command reference

Examples

examples/workspace.yml - Complete workspace configuration
examples/moon.yml - Full project configuration
examples/ci-workflow.yml - GitHub Actions CI workflow

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