mic92/hnix

A Haskell re-implementation of the Nix expression language

hnix

^{(Hackage Matrix Builder)}

Haskell parser, evaluator and type checker for the Nix language.

Prerequisites

Nix is installed and in your $PATH. This is so that nix-store can be used for interacting with store paths, until hnix-store is ready.

Getting Started

$ git clone --recursive https://github.com/haskell-nix/hnix.git
...
$ cd hnix
$ nix-shell
$ cabal configure --enable-tests
$ cabal build
$ cabal test
# To run all of the tests, which takes up to a minute:
$ env ALL_TESTS=yes cabal test
# To run only specific tests (see `tests/Main.hs` for a list)
$ env NIXPKGS_TESTS=yes PRETTY_TESTS=yes cabal test
$ ./dist/build/hnix/hnix --help

Building a Docker container

If you don't have Nix installed, or you'd just like to play around with hnix completely separately from your main system, you can build a Docker container:

$ docker build -t hnix .
$ docker run hnix hnix --eval --expr '1 + 2'

# In order to refer to files under the current directory:
$ docker run -v $PWD/:/tmp/build run hnix hnix default.nix

Building with full debug info

To build hnix for debugging, and with full tracing output and stack traces, use:

$ nix-shell
$ cabal configure --enable-tests --enable-profiling --flags=profiling --flags=tracing
$ cabal build
$ ./dist/build/hnix/hnix -v5 --trace <args> +RTS -xc

Note that this will run quite slowly, but will give the most information as to what might potentially be going wrong during parsing or evaluation.

Building with benchmarks enabled

To build hnix with benchmarks enabled:

$ nix-shell --arg doBenchmarks true
$ cabal configure --enable-tests --enable-benchmarks
$ cabal build
$ cabal bench

Building with profiling enabled

To build hnix with profiling enabled:

$ nix-shell
$ cabal configure --enable-tests --enable-profiling --flags=profiling
$ cabal build
$ ./dist/build/hnix/hnix <args> +RTS -p

Building with GHCJS

From the project root directory, run:

$ NIX_CONF_DIR=$PWD/ghcjs nix-build ghcjs

This will build an hnix library that can be linked to your GHCJS application.

Using the Cachix binary cache

If you're on macOS, you can use the binary cache at Cachix to avoid building the specific dependencies used by hnix. Just use these commands:

nix-env -iA cachix -f https://github.com/NixOS/nixpkgs/tarball/db557aab7b690f5e0e3348459f2e4dc8fd0d9298
cachix use hnix

How you can help

If you're looking for a way to help out, try taking a look here. When you find an issue that looks interesting to you, comment on the ticket to let others know you're working on it; look for others who might have done the same. You can talk with everyone live on Gitter.

When you're ready to submit a pull request, test it with:

git submodule update --init --recursive
nix-shell --run "LANGUAGE_TESTS=yes cabal test"

Make sure that all the tests that were passing prior to your PR are still passing afterwards; it's OK if no new tests are passing.