Why isn't my overlay for a Haskell package working?

[codygman]

edit: answer was silent error from missing argument to callHackageDirect.

I have the following:

final: prev: {

  haskellPackages = 
      prev.haskellPackages.override (old: {
        overrides = final.lib.composeExtensions (old.overrides or (_: _: {})) 
          (hfinal: hprev: {
            ghc = hprev.ghc // { withPackages = hprev.ghc.withHoogle; };
            ghcWithPackages = hfinal.ghc.withPackages;

            # somehow uncommenting this just breaks things
            # witch = prev.haskellPackages.callHackageDirect
            #   { pkg = "witch";
            #     ver = "0.1.1.0";
            #     sha256 = "0000000000000000000000000000000000000000000000000000";
            #   };
	    
          });
      });
}

I would expect it to give me the sha error, but instead when I actually uncomment that code I don't see the package installed. If I leave it commmented as written above I see:

✖1 ❯ sudo nixos-rebuild --flake "$DEVSHELL_ROOT#$1" switch && ghc-pkg list | grep witch
... snip rebuild ...
    witch-0.0.0.5

The overlay is in git:

❯ git ls-files overlays/witch.nix 
overlays/witch.nix

[nrdxp]

have you tried:

final: prev: {
  haskellPackages = prev.haskellPackages.override {
    overrides = hfinal: hprev: {
      ghc = hprev.ghc // { withPackages = hprev.ghc.withHoogle; };
      # ths might be redundant
      ghcWithPackages = hfinal.ghc.withPackages;

      witch = prev.haskellPackages.callHackageDirect {
        pkg = "witch";
        ver = "0.1.1.0";
        sha256 = "0000000000000000000000000000000000000000000000000000";
      };
    };
  };
}

[codygman]

The overlay seems to "erase" witch from my Haskell packages, see below:

devos2  no-evil 「↪ 𝚫 ✔ 📁 」  ⎔ on  (us-east-1) 
❯ git ls-files overlays/witch.nix 
overlays/witch.nix

devos2  no-evil 「↪ 𝚫 ✔ 📁 」  ⎔ on  (us-east-1) 
❯ ghc-pkg list | grep -i witch
    witch-0.0.0.5

devos2  no-evil 「↪ 𝚫 ✔ 📁 」  ⎔ on  (us-east-1) 
❯ cat overlays/witch.nix
final: prev: {
  haskellPackages = prev.haskellPackages.override {
    overrides = hfinal: hprev: {
      ghc = hprev.ghc // { withPackages = hprev.ghc.withHoogle; };
      # ths might be redundant
      ghcWithPackages = hfinal.ghc.withPackages;

      witch = prev.haskellPackages.callHackageDirect {
        pkg = "witch";
        ver = "0.1.1.0";
        sha256 = "0000000000000000000000000000000000000000000000000000";
      };
    };
  };
}

devos2  no-evil 「↪ 𝚫 ✔ 📁 」  ⎔ on  (us-east-1) 
❯ sudo nix shell ".#nixosConfigurations.work-tower.config.system.build.toplevel" -c switch-to-configuration switch
warning: Git tree '/home/cody/devos2' is dirty
stopping the following units: accounts-daemon.service
NOT restarting the following changed units: systemd-fsck@dev-disk-by\x2duuid-CC73\x2dFF6A.service
activating the configuration...
setting up /etc...
reloading user units for cody...
setting up tmpfiles
reloading the following units: dbus.service
restarting the following units: polkit.service
starting the following units: accounts-daemon.service

devos2  no-evil 「↪ 𝚫 ✔ 📁 」  ⎔ on  (us-east-1) 
❯ ghc-pkg list | grep -i witch

[codygman]

The callHackageDirect call was missing the {} argument and silently failed and just used the older version 🙁

[codygman]

This was the fix:

      witch = prev.haskellPackages.callHackageDirect {
        pkg = "witch";
        ver = "0.1.1.0";
        sha256 = "0000000000000000000000000000000000000000000000000000";
-     };
+     } {};