stack build error: attribute ‘ghc822’ missing, at (string):1:53

Question

I am attempting to build my haskell project on NixOS.

Running $ stack build gives the following error.

$ stack build
error: attribute ‘ghc82         


        

Answer 1

As palik commented, changing the resolver version -- in my case changing

resolver: lts-11.3

to

resolver: lts-9.1

in stack.yaml is a work-around. I do not know what the deeper issue is but would be interested to know.

Answer 2

You can provide an old GHC version using a shell.nix file place in the root of your project:

with import (fetchTarball https://github.com/NixOS/nixpkgs/archive/83b35508c6491103cd16a796758e07417a28698b.tar.gz) {};
let ghc = haskell.compiler.ghc802;
in haskell.lib.buildStackProject {
    inherit ghc;
    name = "myEnv";
    buildInputs = [ pcre ];
}

Use a tar url from https://github.com/NixOS/nixpkgs/releases for a version of nixpkgs that contains the GHC version you need.

Then run nix-shell in the root of the project. This will put you into a shell in which you can perform stack build successfully since it would have access to the correct GHC version.

Answer 3

Another option is to use a shell.nix. nixos-18.03 comes with ghc 8.2.2, so you can create a shell.nix like:

with import (builtins.fetchGit {
    url = https://github.com/NixOS/nixpkgs-channels;
    ref = "nixos-18.03";
    rev = "cb0e20d6db96fe09a501076c7a2c265359982814";
}) {};

haskell.lib.buildStackProject {
    name = "my-project";
    buildInputs = [ ghc <otherlibs-here> ];
}

And add the following to your stack.yaml:

nix:
  shell-file: shell.nix

Then stack build as usual.

Answer 4

based on @steve-chávez answer

stack.yaml

resolver: lts-13.19
system-ghc: true
install-ghc: false

nix:
  enable: true
  path: [nixpkgs=./nix/nixpkgs/default.nix]
  shell-file: shell.nix

nix/nixpkgs/default.nix

let
  spec = builtins.fromJSON (builtins.readFile ./revision.json);

  src = import <nix/fetchurl.nix> {
    url = "https://github.com/${spec.owner}/${spec.repo}/archive/${spec.rev}.tar.gz";
    inherit (spec) sha256;
  };
  nixcfg = import <nix/config.nix>;

  nixpkgs = builtins.derivation {
    system = builtins.currentSystem;
    name = "${src.name}-unpacked";
    builder = builtins.storePath nixcfg.shell;
    inherit src;
    args = [
      (builtins.toFile "builder" ''
        $coreutils/mkdir $out
        cd $out
        $gzip -d < $src | $tar -x --strip-components=1
      '')
    ];
    coreutils = builtins.storePath nixcfg.coreutils;
    tar = builtins.storePath nixcfg.tar;
    gzip = builtins.storePath nixcfg.gzip;
  };
in
  import nixpkgs

nix/nixpkgs/update.sh

#!/usr/bin/env nix-shell
#!nix-shell -i bash -p nix curl jq

SCRIPT_DIR=$(dirname "$(readlink -f "$BASH_SOURCE")")

owner="nixos"
repo="nixpkgs-channels"
rev="nixos-unstable"

full_rev=$(curl --silent https://api.github.com/repos/$owner/$repo/git/refs/heads/$rev | jq -r .object.sha)

echo "full_rev=$full_rev"

expected_sha=$(nix-prefetch-url https://github.com/$owner/$repo/archive/$full_rev.tar.gz)

cat >"$SCRIPT_DIR/revision.json" <<EOL
{
  "owner":  "$owner",
  "repo":   "$repo",
  "rev":    "$full_rev",
  "sha256": "$expected_sha"
}
EOL

shell.nix

{
  #
  # there are 2 ways of using stack with nix
  # - define custom packages in `stack.yaml` `packages` option (https://docs.haskellstack.org/en/stable/nix_integration/#additions-to-your-stackyaml)
  # - define custom package in `shell.nix` AND `shell-file: ...` in `stack.yaml` (https://docs.haskellstack.org/en/stable/nix_integration/#additions-to-your-stackyaml)
  #
  # we are using second option

  ghc # stack expect this file to define a function of exactly one argument that should be called ghc
}:


let
  # pkgs = import ./nix/nixpkgs/default.nix {}
  pkgs = import <nixpkgs> {};
in

with pkgs;

haskell.lib.buildStackProject {
  inherit ghc;
  name = "myEnv";
  buildInputs = [ cabal-install ];
}

Answer 5

It seems like your stack wants to retrieve the haskell.packages.ghc822 attribute or perhaps haskell.compiler.ghc822, which is not present in your version of <nixpkgs>.

Please check your channel configuration using sudo nix-channel --list (NixOS) or nix-channel --list. Releases 17.03 and older do not have this attribute. 17.09 and unstable should be fine. To switch your default <nixpkgs> to 17.09, note the name of the channel and run

nix-channel --add https://nixos.org/channels/nixos-17.09 <NAME>

Also run nix-channel --update to make sure you have a recent version. GHC 8.2.2 was added on Oct 31st.

If you don't want to change your channel configuration, I suppose you can set the NIX_PATH environment variable

NIX_PATH=nixpkgs=https://github.com/NixOS/nixpkgs-channels/archive/nixos-unstable.tar.gz stack build