MacOS Catalina: Slow by Design?

Up until the release of Catalina, I've always upgraded to the latest version of macOS within a month or two. But some of the changes this time is really stopping me from upgrading.

As of Catalina, there's no sane way to install the Nix package manager without losing functionality because macOS now disallows creating new files in the root directory[1]. Nix stores its packages in the /nix directory and it's not possible to migrate without causing major disruptions for existing NixOS and other Linux users. This is too bad, since apart from Nix being a nice package manager, it also provides a sane binary package for Emacs. The Homebrew core/cask versions only provides a limited feature set[2][3].

[1]: https://github.com/NixOS/nix/issues/2925

[2]: https://github.com/Homebrew/homebrew-core/issues/31510

[3]: https://github.com/caldwell/build-emacs/search?q=support+is%...

Brew never had this problem because they chose a sane path without corrupting the system directory. It’s a bad design on part of NixOS and one can even say the changes in the macOS were designed to encourage good/sane design.

Nix living at a predefined path is integral to how it works. An executable does not dynamically link to a generic "ncurses" but (via rpath) links to a specific compiled version of ncurses (such as /nix/store/81rb87agmp9cbsvg2xm2n4kp9c6309lv-ncurses-6.2). This is the root of all the benefits of Nix such as being able to install things side-by-side that use different versions of things or upgrade and rollback without problems.

That predefined path being the same (/nix) across all users of nixpkgs is required to be able to share binary packages (you could perhaps build everything from source, but that's a lot of time, more time even than something like gentoo because package updates require all dependencies to be rebuilt as well).

You can call it an insane choice or bad design, but there aren't a whole lot of options here. Could Nix move to a different path? Maybe, but is there a path that all operating systems could abide? If the new path stops working in some future OS, will it still be insane and bad design? Again, maybe, but I happen to love Nix and I use is on macos because it makes my life easier (and I'm on macos for work reasons). I'm willing to bend and do a lot of legwork to be able use Nix, and I'm upset with the Catalina situation.

Can follow some discussion here https://github.com/NixOS/nix/issues/2925