In reply to @bryan.bennett:matrix.org
lxsameer: This is exactly what nix-direnv does, for the record. We create the root in the direnv layout dir (which is kind of what that directory is for - creating state that we need for direnv-related things)

There are multiple things that might require explaining there, so I'll talk about them individually:

• the direnv layout directory is just a directory that state lives in for direnv and its plugins to use. The python layout populates it (in part) with a virtual environment, for instance.
• The root is just a symlink that points to a derivation in the store (more or less). We create those in the layout directory.

here is an example:

        devShells.default = (pkgs.mkShell.override { stdenv = stdenv';}) {
          nativeBuildInputs = buildDevToolsDeps ++ buildToolsDeps ++ shellTools;
          buildInputs = buildDeps ++ testDeps;
          shellHook =
            ''
              BUILDER= ZDOTDIR=${zshDir} zsh -d && exit
            '';
        };

        # This shell is gcc based and we use it only
        # for the mathematics side of our design
        devShells.math = nativePkgs.mkShell {
          #nativeBuildInputs = mathDeps;
          buildInputs = mathDeps;
          shellHook =
            ''
              BUILDER=Math ZDOTDIR=${zshDir} zsh -d && exit
            '';
        };