default.nix

let
  # The following lists specify which overrides need to be applied for which
  # packages.
  # Create a list per override, and add the names of packages in it as strings
  # (using quotes). Do not use the derivations, but the package names.
  # The overrides are applied using `makeOverrides` below.

  # Disable tests for these packages
  dontCheckPackages = [
    "motion-detect-camera"
    "vinyl"
    "postgresql-simple"
    "opaleye-trans"
    "composite-opaleye"
  ];

  # Jailbreak these packages
  doJailbreakPackages = [ "opaleye-trans" "hpio" ];

  # Disable haddocks for these packages
  dontHaddockPackages =
  [ "motion-detect-camera" "opaleye-trans" "composite-opaleye" ];

  # Unmark these packages as broken
  unmarkBrokenPackages = [
    # amazonka is marked as broken (19.09 - 07.01.2020)
    "amazonka"
    "amazonka-core"
    "amazonka-s3"
    "amazonka-sns"
    "amazonka-sqs"
    "amazonka-test"
    "composite-opaleye"
    "composite-base"
    "vinyl"
    "opaleye-trans"
    "phone-numbers"
    "hpio"
  ];
  # This function creates overrides
  makeOverrides = function: names: self: super:
  let
    toPackage = name: {
      inherit name;
      value = function super.${name};
    };
  in builtins.listToAttrs (map toPackage names);


  # servantOverlays = (import ./nix/servant2.nix oldPkgs).overlays;
  # Override config for nixpkgs
  rootOverlays = [
    ( # Packages with non-standard versions
      self: super:
    let

      composeExtensionsList = super.lib.fold super.lib.composeExtensions (_: _: { });

      mainPkgs = _: _: rec {

        # Call the derivation for this project
        motion-detect-camera =
          super.callCabal2nix "motion-detect-camera" ./. { };

        # Call a custom derivation for a dependency
        # For example:
        # - use other version than that in nixpkgs
        # - use a specific git commit
        # - use a fork
        postgresql-simple =
          super.callHackage "postgresql-simple" "0.5.4.0" { };

      };
      # More exotic overrides go here
      manualOverrides = {
        # phone-numbers = haskellPackagesOld.phone-numbers.override {
        #   phonenumber = pkgs.libphonenumber;
        # };
      };
    # apply the overrides
    in super.haskellPackages.override {
      overrides = with super.haskell.lib;
      composeExtensionsList [
        mainPkgs
        (makeOverrides dontCheck dontCheckPackages)
        (makeOverrides doJailbreak doJailbreakPackages)
        (makeOverrides dontHaddock dontHaddockPackages)
        (makeOverrides unmarkBroken unmarkBrokenPackages)
        manualOverrides
      ];
    })
  ];
  # import nixpkgs
  channel = "nixos-19.09";
  pkg-src = builtins.fetchTarball
    ("http://nixos.org/channels/${channel}/nixexprs.tar.xz");

  oldPkgs = import pkg-src {};

  pkgs = import pkg-src {
    overlays = # servantOverlays ++ 
               rootOverlays;
  };

in {
  motion-detect-camera = pkgs.haskellPackages.motion-detect-camera;
  inherit pkgs;
}

inf.txt

╰─$ nix-shell --run 'cabal repl' --show-trace                                                                                                                                             1 ↵
error: while evaluating the attribute 'motion-detect-camera' at /home/ashesh/code/homebot/rpi/motion-detect-camera/release.nix:106:3:
while evaluating anonymous function at /nix/store/c3ilr85kwjiiq4xi6x0grj6sswqglrm4-source/pkgs/top-level/impure.nix:15:1, called from /home/ashesh/code/homebot/rpi/motion-detect-camera/release.nix:100:10:
while evaluating anonymous function at /nix/store/c3ilr85kwjiiq4xi6x0grj6sswqglrm4-source/pkgs/top-level/default.nix:20:1, called from /nix/store/c3ilr85kwjiiq4xi6x0grj6sswqglrm4-source/pkgs/top-level/impure.nix:84:1:
while evaluating anonymous function at /nix/store/c3ilr85kwjiiq4xi6x0grj6sswqglrm4-source/pkgs/stdenv/booter.nix:42:1, called from /nix/store/c3ilr85kwjiiq4xi6x0grj6sswqglrm4-source/pkgs/top-level/default.nix:108:10:
while evaluating 'dfold' at /nix/store/c3ilr85kwjiiq4xi6x0grj6sswqglrm4-source/pkgs/stdenv/booter.nix:60:27, called from /nix/store/c3ilr85kwjiiq4xi6x0grj6sswqglrm4-source/pkgs/stdenv/booter.nix:136:4:
while evaluating 'go' at /nix/store/c3ilr85kwjiiq4xi6x0grj6sswqglrm4-source/pkgs/stdenv/booter.nix:63:18, called from /nix/store/c3ilr85kwjiiq4xi6x0grj6sswqglrm4-source/pkgs/stdenv/booter.nix:72:13:
while evaluating 'folder' at /nix/store/c3ilr85kwjiiq4xi6x0grj6sswqglrm4-source/pkgs/stdenv/booter.nix:89:33, called from /nix/store/c3ilr85kwjiiq4xi6x0grj6sswqglrm4-source/pkgs/stdenv/booter.nix:68:18:
while evaluating 'allPackages' at /nix/store/c3ilr85kwjiiq4xi6x0grj6sswqglrm4-source/pkgs/top-level/default.nix:98:17, called from /nix/store/c3ilr85kwjiiq4xi6x0grj6sswqglrm4-source/pkgs/stdenv/booter.nix:101:12:
while evaluating anonymous function at /nix/store/c3ilr85kwjiiq4xi6x0grj6sswqglrm4-source/pkgs/top-level/stage.nix:12:1, called from /nix/store/c3ilr85kwjiiq4xi6x0grj6sswqglrm4-source/pkgs/top-level/default.nix:98:26:
while evaluating 'fix' at /nix/store/c3ilr85kwjiiq4xi6x0grj6sswqglrm4-source/lib/fixed-points.nix:19:9, called from /nix/store/c3ilr85kwjiiq4xi6x0grj6sswqglrm4-source/pkgs/top-level/stage.nix:248:3:
while evaluating 'extends' at /nix/store/c3ilr85kwjiiq4xi6x0grj6sswqglrm4-source/lib/fixed-points.nix:69:24, called from /nix/store/c3ilr85kwjiiq4xi6x0grj6sswqglrm4-source/lib/fixed-points.nix:19:20:
while evaluating 'extends' at /nix/store/c3ilr85kwjiiq4xi6x0grj6sswqglrm4-source/lib/fixed-points.nix:69:24, called from /nix/store/c3ilr85kwjiiq4xi6x0grj6sswqglrm4-source/lib/fixed-points.nix:69:42:
while evaluating anonymous function at /home/ashesh/code/homebot/rpi/motion-detect-camera/release.nix:54:13, called from /nix/store/c3ilr85kwjiiq4xi6x0grj6sswqglrm4-source/lib/fixed-points.nix:69:67:
infinite recursion encountered, at /home/ashesh/code/homebot/rpi/motion-detect-camera/release.nix:81:8