nix-shell behaves assimetrically pointing at local default.nix and using global ~/.nixpkgs/config.nix tree

abc.cabal

name:                abc
version:             0.1.0.0
license-file:        LICENSE
build-type:          Simple
cabal-version:       >=1.10

executable abc
  main-is:             Main.hs
  build-depends:       base >=4.7 && <4.8
  default-language:    Haskell2010

config.nix

# ~/.nixpkgs/config.nix
pkgs : {
  packageOverrides = pkgs : rec {
    myHaskellPackages =
      let
        callPackage = pkgs.lib.callPackageWith myHaskellPackages;
      in
        pkgs.recurseIntoAttrs (pkgs.haskellPackages.override {
          extension = self : _ : {
            abc = self.callPackage ../path/to/package { haskellPackages = myHaskellPackages; };
          };
        });
  };
}

default.nix

{ haskellPackages ? (import <nixpkgs> {}).haskellPackages }:

haskellPackages.cabal.mkDerivation (self: {
  pname = "abc";
  version = "0.1.0.0";
  src = ./.;
  isLibrary = false;
  isExecutable = true;
  meta = {
    license = self.stdenv.lib.licenses.mit;
    platforms = self.ghc.meta.platforms;
  };
})

Main.hs

main = print 1

whyyy

>> nix-shell default.nix --command 'abc'
bash: abc: command not found
>> nix-shell -p myHaskellPackages.abc --command 'abc'
1

It's all about -p flag.

So the solution is

>>  nix-shell -p '(haskellPackages.callPackage ./default.nix { haskellPackages = haskellPackages; })' --command 'abc'
1