NeoHaskell

NeoHaskell is a dialect of Haskell that is focused on newcomer-friendliness and productivity.

It is designed to be easy to learn and use, while also being powerful enough to release your app with minimum effort and maximum confidence.

Welcome to the contributor guide

If you want to learn about NeoHaskell itself, checkout the NeoHaskell website.

This guide is intended to streamline the process of contributing to the NeoHaskell tooling.

The repository will be a mono-repo that contains all the different parts of NeoHaskell.

Installing the required tools

(This assumes that you're using MacOS, WSL2 or Linux)

Install Nix with flakes enabled
Run nix develop to enter the development shell
Run cabal update && cabal build all

Binary Cache (Faster Builds)

The project uses Cachix to cache build artifacts. The flake.nix is pre-configured to use our cache, so nix develop should automatically prompt you to trust it on first run.

If you want to explicitly enable it (or if you have a restrictive Nix config):

# Install cachix (if not already installed) nix-env -iA cachix -f https://cachix.org/api/v1/install Add the NeoHaskell cache

cachix use neohaskell

This dramatically speeds up the first nix develop (from ~30 min to ~2 min).

The recommended IDE for any NeoHaskell project is Visual Studio Code.

Get the code

Fork this repository
git clone <url to your fork>
cd NeoHaskell && code .

Install the recommended extensions

When opening the project for the first time, you will be prompted to install the recommended extensions, install them.

Code Formatting

This project uses the fourmolu formatter for consistent Haskell code styling. When using VS Code with the recommended extensions:

Code will automatically format on save
The formatter settings are controlled by the fourmolu.yaml file in the root directory

Linting

This project uses hlint, it will automatically be run in VSCode by the recommended extension. To run manually:

hlint .

Running Tests

The core library tests are split into domain-specific suites that run in parallel on CI:

# Run all tests cabal test all Run specific test suites

cabal test nhcore-test-core # Core primitives (fast) cabal test nhcore-test-auth # Auth & JWT tests cabal test nhcore-test-service # Service layer (requires PostgreSQL) cabal test nhcore-test-integration # Integration tests

Note: nhcore-test-service requires a PostgreSQL instance. You can start one with:

docker run -d --name neohaskell-postgres \
  -e POSTGRES_USER=neohaskell \
  -e POSTGRES_PASSWORD=neohaskell \
  -e POSTGRES_DB=neohaskell \
  -p 5432:5432 \
  postgres:16-alpine