We don't check for existence on purpose so that you don't need to log out when a path element is first created. For example, if ~/.nix-profile/bin doesn't exist, it should still be added to $PATH so that you don't need to log in again after running nix-env -i for the first time.

The consequence of this is that users need to relogin after a configuration change has been done by the administrator. In short, this is not just an improvement.

I would like to see designs implemented which do not break the existing semantics. One such design is patching fish (there are not that many programs that work like fish regarding the PATH). There are other designs.

@edolstra haha, we just wrote the exact same thing :)

I understand, that is convenient. Well, I can't imagine how to patch fish without removing the warning entirely. Maybe we could patch foreign-env instead.