Nix Haskell developPackages Demo

README.md

Quickstart

1. Make a new directory and place the other files at their described paths relative to that directory's root

• library.DemoLib.hs should be placed at library/DemoLib.hs, gists don't allow a naming convention of library/DemoLib.hs

2. Run the following command:

nix-shell -E 'let pkgs = import ./pinned.nix {}; pkg =  pkgs.haskellPackages.developPackage { root = ./.; }; in pkg.overrideAttrs (attrs: { buildInputs = attrs.buildInputs ++ [ pkgs.cabal-install]; })'

3. Run cabal update (to ensure that there's a valid $HOME/.cabal directory with relevant Hackage information, even though we're not going to use it)
4. Run cabal build and verify that the package builds.

demo.cabal

cabal-version: 3.0
name:
  demo
version:
  0.0.1
synopsis:
  Demonstrate a pinned Nix package set with Nix Haskell developPackage
license:
  MIT
author:
  jkachmar
build-type:
  Simple
extra-source-files:
  readme.md

-------------------------------------------------------------------------------
common common
  default-language: Haskell2010

  ghc-options:
    -Weverything
    -Wno-all-missed-specializations
    -Wno-implicit-prelude
    -Wno-missing-export-lists
    -Wno-missing-exported-signatures
    -Wno-missing-import-lists
    -Wno-missing-local-signatures
    -Wno-missed-specialisations
    -Wno-monomorphism-restriction
    -Wno-safe
    -Wno-unsafe

  default-extensions:
    OverloadedStrings
    ScopedTypeVariables

  build-depends:
    -- Convenient libraries to keep around that are included with GHC anyway
      base
    -- External library
    , unordered-containers

-------------------------------------------------------------------------------
library
  import: common
  hs-source-dirs: library
  exposed-modules:
    DemoLib

library.DemoLib.hs

module DemoLib (demo) where

demo :: IO ()
demo = putStrLn "Hello!"

pinned.nix

import (
  builtins.fetchTarball {
    # Latest commit on the nixpkgs-unstable branch as of 12 June 2020
    url = "https://github.com/nixos/nixpkgs/archive/dcb64ea42e64aaecd8e6fef65cc86245c9666818.tar.gz";
    sha256 = "0i77sgs0gic6pwbkvk9lbpfshgizdrqyh18law2ji1409azc09w0";
  }
)