nix-shell not working w/ local executable project

default.nix

# This file was auto-generated by cabal2nix. Please do NOT edit manually!

{ cabal, convertible, exceptions, HDBC, HDBCSqlite3, monadHdbc, mtl
, options, text, time, transformers
}:

cabal.mkDerivation (self: {
  pname = "scrumgr";
  version = "0.1.0.0";
  src = ./.;
  isLibrary = false;
  isExecutable = true;
  buildDepends = [
    convertible exceptions HDBC HDBCSqlite3 monadHdbc mtl options text
    time transformers
  ];
  meta = {
    homepage = "https://github.com/JLimperg/scrumgr";
    license = self.stdenv.lib.licenses.mit;
    platforms = self.ghc.meta.platforms;
  };
})

shell.nix

let pkgs = (import <nixpkgs> {});
    haskellPackages = pkgs.recurseIntoAttrs (pkgs.haskellPackages.override {
        extension = self : super :
        let callPackage = self.callPackage;
        in {
           # add cabal package dependencies here, like so:
           # prettyCompact = callPackage ./nix/pretty-compact.nix {};
           monadHdbc = haskellPackages.callPackage ./nix/monad-hdbc.nix {};
           thisPackage = haskellPackages.callPackage (import ./default.nix) {};
        };});
in pkgs.myEnvFun {
    name = haskellPackages.thisPackage.name;
    buildInputs = 
       [(haskellPackages.ghcWithPackages (hs: ([
         hs.cabalInstall
         # add other build tools here
       ] ++ haskellPackages.thisPackage.propagatedNativeBuildInputs)))];
     }