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 ‘ghc822’ missing, at (string):1:53
(use ‘--show-trace’ to show detailed location information)

What does this error mean and how could I proceed? When I run $ stack build --show-trace as suggested, I get the following output, which I do not understand either.

$ stack build --show-trace
Invalid option `--show-trace'

Usage: stack build [TARGET] [--dry-run] [--pedantic] [--fast]
                   [--ghc-options OPTIONS] [--flag PACKAGE:[-]FLAG]
                   ([--dependencies-only] | [--only-snapshot] |
                   [--only-dependencies]) ([--file-watch] | [--file-watch-poll])
                   [--exec CMD [ARGS]] [--only-configure] [--trace] [--profile]
                   [--no-strip] [--[no-]library-profiling]
                   [--[no-]executable-profiling] [--[no-]library-stripping]
                   [--[no-]executable-stripping] [--[no-]haddock]
                   [--haddock-arguments HADDOCK_ARGS] [--[no-]open]
                   [--[no-]haddock-deps] [--[no-]haddock-internal]
                   [--[no-]haddock-hyperlink-source] [--[no-]copy-bins]
                   [--[no-]copy-compiler-tool] [--[no-]prefetch]
                   [--[no-]keep-going] [--[no-]force-dirty] [--[no-]test]
                   [--[no-]rerun-tests] [--ta|--test-arguments TEST_ARGS]
                   [--coverage] [--no-run-tests] [--[no-]bench]
                   [--ba|--benchmark-arguments BENCH_ARGS] [--no-run-benchmarks]
                   [--[no-]reconfigure] [--[no-]cabal-verbose]
                   [--[no-]split-objs] [--skip ARG] [--help]
  Build the package(s) in this directory/configuration

---

I tried changing my channel to nixos-17.09 instead of nixos-unstable (and running nix-channel --update), but still get the same error.

Output of $ nix-channel --list is shown below.

$ nix-channel --list
stack https://nixos.org/channels/nixos-17.09
nixos https://nixos.org/channels/nixos-17.09

---

The output of $ nix-env -qaPA 'nixos.haskell.compiler' shows ghc822 to be found.

$ nix-env -qaPA 'nixos.haskell.compiler'
warning: name collision in input Nix expressions, skipping ‘/home/matthew/.nix-defexpr/channels_root/nixos’
nixos.haskell.compiler.ghc6102Binary           ghc-6.10.2-binary
nixos.haskell.compiler.ghc704                  ghc-7.0.4
nixos.haskell.compiler.ghc704Binary            ghc-7.0.4-binary
nixos.haskell.compiler.ghc7102                 ghc-7.10.2
nixos.haskell.compiler.integer-simple.ghc7102  ghc-7.10.2
nixos.haskell.compiler.ghc7103                 ghc-7.10.3
nixos.haskell.compiler.integer-simple.ghc7103  ghc-7.10.3
nixos.haskell.compiler.integer-simple.ghc742   ghc-7.4.2
nixos.haskell.compiler.ghc742                  ghc-7.4.2
nixos.haskell.compiler.ghc742Binary            ghc-7.4.2-binary
nixos.haskell.compiler.ghc763                  ghc-7.6.3
nixos.haskell.compiler.ghc783                  ghc-7.8.3
nixos.haskell.compiler.integer-simple.ghc783   ghc-7.8.3
nixos.haskell.compiler.ghc784                  ghc-7.8.4
nixos.haskell.compiler.integer-simple.ghc784   ghc-7.8.4
nixos.haskell.compiler.ghc801                  ghc-8.0.1
nixos.haskell.compiler.integer-simple.ghc801   ghc-8.0.1
nixos.haskell.compiler.ghc802                  ghc-8.0.2
nixos.haskell.compiler.integer-simple.ghc802   ghc-8.0.2
nixos.haskell.compiler.integer-simple.ghc821   ghc-8.2.1
nixos.haskell.compiler.ghc821                  ghc-8.2.1
nixos.haskell.compiler.integer-simple.ghc822   ghc-8.2.2
nixos.haskell.compiler.ghc822                  ghc-8.2.2
nixos.haskell.compiler.integer-simple.ghcHEAD  ghc-8.3.20170808
nixos.haskell.compiler.ghcHEAD                 ghc-8.3.20170808
nixos.haskell.compiler.ghcjs                   ghcjs-0.2.0
nixos.haskell.compiler.ghcjsHEAD               ghcjs-0.2.020170323
nixos.haskell.compiler.jhc                     jhc-0.8.2
nixos.haskell.compiler.uhc                     uhc-1.1.9.4

I installed ghc8.2.2 via $ nix-env -iA nixos.haskell.compiler.ghc822, and $ ghc --version now returns

$ ghc --version
The Glorious Glasgow Haskell Compilation System, version 8.2.2

However, I still get the error error: attribute ‘ghc822’ missing, at (string):1:54 when attempting to run $ stack build.

Also, I attempted to see what ghc version my stack is using after this install, and this led to the same attribute ‘ghc822’ missing error.

$ stack ghc -- --version
error: attribute ‘ghc822’ missing, at (string):1:54
(use ‘--show-trace’ to show detailed location information)

Answer 1

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 2

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 3

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