Nix

What's Nix?

Nix is a wickedly powerful package manager and build system that allows you to create reproducible development environments. It ensures that your project dependencies are consistent across different machines, making it easier to onboard new developers and maintain your codebase.

Nix uses a declarative approach to define environments, meaning you can specify exactly what tools and versions you need without worrying about conflicts or version mismatches. For matt-init projects, Nix provides a great way to manage Node.js, pnpm, and other development tools in a single configuration file.

Getting Started

Prerequisites

1. Install Nix - Follow the official installation guide
2. Enable flakes - Add to ~/.config/nix/nix.conf:

experimental-features = nix-command flakes

Entering the Development Shell

# Enter the development shell
nix develop

Note: If this is your first time using Nix, you may not appreciate how sick that just was: in a single command, you installed all the necessary tools for your project, down to the exact version, and entered a shell with them available. It. Just. Works.

What You Get

When you enter the shell, you'll have access to:

• Node.js
• pnpm (latest stable)
• Turso CLI (for database management) (if it was selected during setup)
• sqld (local SQLite server) (if it was selected during setup)
• Development tools (alejandra for formatting, etc)

Configuration

Main Flake (flake.nix)

This isn't the exciting part. This file is the entry point for your Nix configuration. It defines the inputs (like nixpkgs and flake-utils) and outputs (like development shells and formatters).

{
  description = "my-cool-app";

  inputs = {
    nixpkgs.url = "github:nixos/nixpkgs/release-24.11";
    flake-utils.url = "github:numtide/flake-utils";
  };

  outputs = {
    self,
    flake-utils,
    nixpkgs,
    ...
  }:
    flake-utils.lib.eachDefaultSystem (
      system: let
        pkgs = import nixpkgs {inherit system;};
      in {
        devShell = pkgs.callPackage ./nix/devShell.nix {};
        formatter = pkgs.alejandra;
      }
    );
}

Development Shell (nix/devShell.nix)

Here's the meat and potatoes of your Nix setup. This file defines the development environment, including all the tools you need for your project.

{
  mkShell,
  alejandra,
  bash,
  nodejs,
  pnpm,
  turso-cli,
  sqld,
}:
mkShell rec {
  name = "my-cool-app";

  packages = [
    bash
    nodejs
    pnpm

    # Required for CI for format checking.
    alejandra

    turso-cli
    sqld
  ];
}

Common Operations

Adding New Tools

Edit nix/devShell.nix to add more development tools:

{
  ...,
  newPackageINeeded,
  ...,
}:
mkShell rec {
  name = "my-cool-app";

  packages = [
    ...
    newPackageINeeded
    ...
  ];
}

Updating Dependencies

# Update all inputs to latest
nix flake update

# Update specific input
nix flake lock --update-input nixpkgs

# Check what changed
nix flake lock --update-input nixpkgs --print-build-logs

Resources