NIX_PATH is not updated after nixos-rebuild switch

[milahu]

either this is deliberate to keep the system stable
or this is not implemented because it affects the legacy nix tools nix-shell and nix-build

environment

nixpkgs 01441e1

reproduce

$ echo $NIX_PATH | tr : $'\n' | grep ^nixpkgs=
nixpkgs=/nix/store/qb3dg4cx5jzk3pa8szzi0ziwnqy33p50-source

$ ( cd /etc/nixos && sudo nix flake lock --update-input nixpkgs )

$ sudo nixos-rebuild switch

$ echo $NIX_PATH | tr : $'\n' | grep ^nixpkgs=
nixpkgs=/nix/store/qb3dg4cx5jzk3pa8szzi0ziwnqy33p50-source

$ source /etc/set-environment

$ echo $NIX_PATH | tr : $'\n' | grep ^nixpkgs=
nixpkgs=/nix/store/0axp4y6hffffs95l5865szvpcmq9g08p-source

problem

/etc/profile

  if [ -z "$__NIXOS_SET_ENVIRONMENT_DONE" ]; then
      . /nix/store/4rd12751lhvvinlkcc0ij3rs2h6g2r4l-set-environment
  fi

workaround

~/.bashrc

# force update of NIX_PATH
# FIXME this should be done somewhere else...
# usually in /etc/profile but that has
#   if [ -z "$__NIXOS_SET_ENVIRONMENT_DONE" ]; then
#       . /nix/store/4rd12751lhvvinlkcc0ij3rs2h6g2r4l-set-environment
#   fi
source /etc/set-environment