Given the following cached-shell.nix:

{ pkgs ? import <nixpkgs> {} }: pkgs.mkShell { shellHook = ''  echo "Initialize something here (maybe a Postgres Database, for example)"  export SOMEVAR="$OTHERVAR"  ''; }

This is how nix-shell behaves:

$ OTHERVAR=201 nix-shell cached-shell.nix Initialize something here (maybe a Postgres Database, for example) $ echo $SOMEVAR 201

And this is cached-nix-shell (the echo command outputs nothing both with a cached shell and when caching it the first time):

$ OTHERVAR=201 cached-nix-shell cached-shell.nix $ echo $SOMEVAR 

So I think there's a difference in behavior. Would it be correct to say that the correct behavior for cached-nix-shell should be:

1. Cache a derivation which is the shell derivation without its shellHook attribute. However, take care to cache dependencies that might be brought in by ${some-nix-var} in shellHook's body.
2. Run shellHook everytime cached-nix-shell runs.

Thanks in advance!