Comment by 16
6 hours ago
It sounds like you're talking about home-manager, which is a third-party Nix module, not Nix itself. I've been using Nix happily for several years now for work and personal without needing to use home-manager at all (since I don't like it either).
It was just an example. Other packages could also set new variables / parameters in their configuration. It might not be a problem in the beginning if the variable is just repopulated, but it might blow up in your face in the future.
If you use Nix you're completely blind to that unless you A) religiously check your state or B) use another tool like 'git' or 'nh'. Like I said, it's a blind spot, both figuratively and literally.
This problem may be specific to Darwin because on NixOS I've never had a file overwritten by nix (even with home manager). When a file is managed by nix it's a symlink to a read-only filesystem (/nix/store), so no program can overwrite it. If the symlink is replaced by a regular file, nix refuses to reapply.
Correct for data, not for config files. Config files are stateful unless you do the procedure I mentioned, because they're generated at first application launch.
If you try to symlink into an existing file Nix will indeed complain, which is why you have to erase the config file and then put yours in place. You can either write it out from a .nix file (pure reproducibility) or from symlink copy from a file managed by git (technically impure but effectively reproducible).
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