Monorepo with Shared Configurations

This guide shows how to structure a monorepo where multiple services share common configurations.

Project Structure

my-monorepo/
├── shared/
│   └── devenv.nix       # Shared configurations
├── services/
│   ├── api/
│   │   ├── devenv.yaml
│   │   └── devenv.nix
│   └── frontend/
│       ├── devenv.yaml
│       └── devenv.nix

Shared Configuration

Create a shared configuration with common settings:

{ pkgs, ... }: {
  packages = [
    pkgs.curl
    pkgs.jq
  ];

  services.postgres = {
    enable = true;
    initialDatabases = [
      { name = "myapp"; }
    ];
  };

  git-hooks.hooks = {
    prettier.enable = true;
    nixpkgs-fmt.enable = true;
  };
}

Service Configuration

API Service

Each service imports the shared configuration using an absolute import path. Paths starting with / are resolved from the repository root (where .git is located), allowing services in different directories to reference shared configurations consistently.

imports:
  - /shared

{ pkgs, ... }: {
  # Node.js for the API
  languages.javascript = {
    enable = true;
    package = pkgs.nodejs_20;
  };

  # API-specific environment
  env = {
    API_PORT = "3000";
    SERVICE_NAME = "api";
  };

  # API scripts
  scripts = {
    dev.exec = "npm run dev";
    test.exec = "npm test";
  };
}

Frontend Service

imports:
  - /shared

{ pkgs, ... }: {
  languages.javascript = {
    enable = true;
    package = pkgs.nodejs_20;
  };

  # Frontend scripts
  scripts = {
    dev.exec = "npm run dev";
    build.exec = "npm run build";
  };
}

Referencing the Repository Root

When working in a monorepo, you often need to reference paths relative to the repository root. Use config.git.root to get the absolute path to the git repository root.

This is particularly useful for running processes from specific directories:

{ pkgs, config, ... }: {
  processes.api.exec = {
    exec = "npm run dev";
    cwd = "${config.git.root}/services/api";
  };

  processes.frontend.exec = {
    exec = "npm run dev";
    cwd = "${config.git.root}/services/frontend";
  };
}

This allows you to run multiple service processes from a single devenv shell, regardless of which directory you’re in.

Working with Services

Enter a specific service environment:

cd services/api
devenv shell

The API service will have access to:

All packages from shared/devenv.nix (git, curl, jq)
The PostgreSQL database service
Common environment variables (PROJECT_NAME, ENVIRONMENT, DATABASE_URL)
Its own specific settings (API_PORT, SERVICE_NAME)

Similarly, the frontend service inherits the shared configuration while maintaining its own specific settings.