common-shell

.nixpkgs-config.nix

{
  allowUnfree = true;

  packageOverrides = pkgs: with pkgs; {
    pythonDevEnv = stdenv.mkDerivation {
      name = "basic-python-env";
      buildInputs = [
        openssh
        git
        stdenv
      ];
      shellHook =
        ''
          VIRTUAL_ENV="$dev_path/$env_name"
          if [ ! -d "$env_name" ]
          then
              virtualenv --python=python3.4 "$VIRTUAL_ENV"
          fi

          export VIRTUAL_ENV

          PATH="$VIRTUAL_ENV/bin:$PATH"
          export PATH

          if [ -n "$PYTHONHOME" ] ; then
              unset PYTHONHOME
          fi

          if [ -z "$VIRTUAL_ENV_DISABLE_PROMPT" ] ; then
              if [ "x" != x ] ; then
                  PS1="$PS1"
              else
              if [ "`basename \"$VIRTUAL_ENV\"`" = "__" ] ; then
                  # special case for Aspen magic directories
                  # see http://www.zetadev.com/software/aspen/
                  PS1="[`basename \`dirname \"$VIRTUAL_ENV\"\``] $PS1"
              else
                  PS1="(`basename \"$VIRTUAL_ENV\"`)$PS1"
              fi
              fi
              export PS1
          fi

          alias pydoc="python -m pydoc"
        '';
    };
  };
}

nix-shell-trace

$ nix-shell --show-trace ~/.shells/test.nix 
error: while evaluating ‘overrideDerivation’ at "/nix/var/nix/profiles/per-user/root/channels/nixos/nixpkgs/lib/customisation.nix":65:32, called from "/home/sjagoe/.shells/test.nix":6:11:
while evaluating ‘makeOverridable’ at "/nix/var/nix/profiles/per-user/root/channels/nixos/nixpkgs/lib/customisation.nix":56:24, called from "/nix/var/nix/profiles/per-user/root/channels/nixos/nixpkgs/lib/customisation.nix":66:13:
while evaluating anonymous function at "/nix/var/nix/profiles/per-user/root/channels/nixos/nixpkgs/lib/customisation.nix":66:30, called from "/nix/var/nix/profiles/per-user/root/channels/nixos/nixpkgs/lib/customisation.nix":58:12:
while evaluating ‘overrideDerivation’ at "/nix/var/nix/profiles/per-user/root/channels/nixos/nixpkgs/lib/customisation.nix":34:29, called from "/nix/var/nix/profiles/per-user/root/channels/nixos/nixpkgs/lib/customisation.nix":66:36:
while evaluating ‘addPassthru’ at "/nix/var/nix/profiles/per-user/root/channels/nixos/nixpkgs/lib/customisation.nix":109:22, called from "/nix/var/nix/profiles/per-user/root/channels/nixos/nixpkgs/lib/customisation.nix":37:8:
attempt to call something which is not a function but a set, at "/nix/var/nix/profiles/per-user/root/channels/nixos/nixpkgs/lib/customisation.nix":36:45

test-minimal.nix

with import <nixpkgs> {};
with pkgs.python34Packages;

{
  pyEnv = stdenv.overrideDerivation pythonDevEnv (attrs: {});
}

test.nix

with import <nixpkgs> {};
with pkgs.python34Packages;

{
  pyEnv = stdenv.overrideDerivation pythonDevEnv (attrs: {
    name = "test";
    buildInputs = attrs.buildInputs ++ [
      python34
      python34Packages.pip
      python34Packages.virtualenv
    ];
    shellHook =
      ''
        dev_path=/home/sjagoe/some/path
        env_name=test
      '' + attrs.shellHook;
  });
}