Arch Linux

Description:
After installing [nix] 2.5.1-1 and following https://wiki.archlinux.org/title/Nix#Configuration, opening a shell
that sources /etc/profile has the path "$HOME/.nix-profile/bin" as the first two entries in $PATH.

Potential Reason for the above:
[nix] installs both of the following files:
* /etc/profile.d/nix-daemon.sh(generated from https://github.com/NixOS/nix/blob/2.5.1/scripts/nix-profile-daemon.sh.in)
* /etc/profile.d/nix.sh(generated from https://github.com/NixOS/nix/blob/2.5.1/scripts/nix-profile.sh.in)
nix.sh and nix-daemon.sh, when not preceded by a full path, will hereafter be used to refer only to these installed files.

I believe that nix.sh is not supposed to be a part of this package.


Steps taken to arrive at this belief:
Both nix-daemon.sh and nix.sh seem to achieve similar purposes:
* both export $NIX_SSL_CERT_FILE (though nix-daemon.sh looks in the nix profile in /nix too, does not change a preset value and nix.sh looks in an extra position - commented with # old cacert in Nix profile - which may have something to do with it not having been updated in two years)
* both export $NIX_PROFILES as "/nix/var/nix/profiles/default $HOME/.nix-profile"
* both prepend $HOME/.nix_profile/bin to $PATH but nix-daemon.sh also prepends /nix/var/nix/profiles/default/bin

However, nix-daemon.sh is only meant to be run once (by means of setting a shell variable and then checking for it) ( https://github.com/NixOS/nix/blob/2.5.1/scripts/nix-profile-daemon.sh.in#L1-L3),
while nix.sh is meant to run whenever $HOME and $USER are defined, as it's supposed to set up the per-user profile ( https://github.com/NixOS/nix/blob/2.5.1/scripts/nix-profile.sh.in#L1-L3), it also edits $MANPATH if it exists.

This would lead one to believe that both of these are not meant to be run at the same time,
to confirm this I installed nixOS on the official archlinux vagrant box, version 20211201.40458 ( https://app.vagrantup.com/archlinux/boxes/archlinux/versions/20211201.40458),
using `sh <(curl -L https://nixos.org/nix/install) --daemon`, following the multi-user-installation instructions in the nix manual ( https://nixos.org/manual/nix/stable/installation/installing-binary.html#multi-user-installation).

This did install a file at /etc/profile.d/nix.sh, however, this is not the same as our nix.sh and its sole purpose is to source /nix/var/nix/profiles/default/etc/profile.d/nix-daemon.sh, which is identical to the nix-daemon.sh installed by [nix], identical entries sourcing nix-daemon.sh were appended to /etc/bash.bashrc, /etc/zsh/zshrc and /etc/zsh/zshrc.

The install also created 32 nixbld users, a nix store at /nix, and added the nix-daemon socket and service, and I confirmed that the install works by running `nix-shell -p nix-info --run "nix-info -m"` which states that it's a "multi-user" install ( https://gist.github.com/AulonSal/c11e077f8e068356ecb833d214dbf7e6) and thus would be termed a "multi-user nix install on a linux system running systemd".

I also then installed nix on another vm based on the same box, this time going for the "single-user" install with `sh <(curl -L https://nixos.org/nix/install) --no-daemon"` ( https://nixos.org/manual/nix/stable/installation/installing-binary.html#single-user-installation),
this modified $HOME/.bashrc and $HOME/.zshrc to source /home/vagrant/.nix-profile/etc/profile.d/nix.sh, which is identical to our nix.sh.

As a final sanity check, I deleted /etc/profile.d/nix.sh from my own system, rebooted, and nix appears to be working fine.

Conclusion:
All of this would suggest that nix.sh is not meant to be sourced by a multi-user nix install on linux, thus it should be removed
from the [nix] package.


How to fix the package:
Adding `rm -rf "$pkgdir/etc/profile.d/nix.sh"` right after line99 (`rm -rf "$pkgdir/etc/init"`) in the PKGBUILD ( https://github.com/archlinux/svntogit-community/blob/packages/nix/trunk/PKGBUILD#L99) should fix it.
Also, $srcdir/nix-2.5.1/scripts/local.mk ( https://github.com/NixOS/nix/blob/2.5.1/scripts/local.mk) adds nix-profile.sh (the file nix.sh is generated from) to "noinst-scripts" and that may have some significance?


Additional info:
pkgversion: 2.5.1-1
The PKGBUILD appears to not be idempotent.
It has to do with the fact that after the first build, $srcdir/$pkgbase-$pkgver/nix-docs (created in line102) is not deleted after its contents are moved out, thus when line102 is run in the next build, in package_nix(), the $pkgdir/usr/share/doc directory is move inside of nix-docs, thus the docs go inside $srcdir/$pkgbase-$pkgver/nix-docs/doc/nix and package_nix-docs() fails at line 113.
Adding `rmdir nix-docs` at the end of package_nix-docs() should make it idempotent if one were inclined to do so.


Steps to reproduce:
* Install [nix] v2.5.1-1
* Open a shell that does not make $PATH entries unique automatically(zsh seems to do this) and sources /etc/profile
* run `echo $PATH`

If somebody wishes to repro the installs on vagrant, beware that the arch box threw warnings (Warning: Connection refused. Retrying...) for minutes before continuing (might be something wrong with my config).