Emacs creates native-lisp directories unconditionally

[tmuehlbacher]

Describe the bug

Emacs will try to create a directory structure like
share/emacs/native-lisp/29.1-ef7c54ae/ for every path in
$NIX_PROFILES. This seems to be because of the code in
pkgs/applications/editors/emacs/site-start.el.

On NixOS, the NIX_PROFILES environment variable may contain invalid
paths, for example ~/.nix-profile may not exist. This causes Emacs to
create the full directory structure for that path. This also causes
issues if Nix afterwards wants to create ~/.nix-profile as a symlink
but it already exists as a directory.

Steps To Reproduce

$ for i in $NIX_PROFILES; do file $i; done
/run/current-system/sw: symbolic link to /nix/store/d2p2vm19a44pf51c4pcjcw8p9hliv6x4-system-path
/nix/var/nix/profiles/default: symbolic link to /nix/var/nix/profiles/per-user/root/profile
/etc/profiles/per-user/tom: symbolic link to /etc/static/profiles/per-user/tom
/home/tom/.nix-profile: cannot open `/home/tom/.nix-profile' (No such file or directory)

$ emacs
C-x C-e

$ for i in $NIX_PROFILES; do file $i; done
/run/current-system/sw: symbolic link to /nix/store/d2p2vm19a44pf51c4pcjcw8p9hliv6x4-system-path
/nix/var/nix/profiles/default: symbolic link to /nix/var/nix/profiles/per-user/root/profile
/etc/profiles/per-user/tom: symbolic link to /etc/static/profiles/per-user/tom
/home/tom/.nix-profile: directory

Expected behavior

The code in site-start.el should filter NIX_PROFILES down to only
paths that already exist.

Additional context

Ideally, NIX_PROFILES would only include paths that exist in the first
place, but this is not the case. #241518 also seems related.

Notify maintainers

@AndersonTorres
@adisbladis
@Atemu
@jwiegley
@lovek323
@matthewbauer

Metadata

• system: "x86_64-linux"
• host os: Linux 6.4.8, NixOS, 23.11 (Tapir), 23.11.20230807.5a8e924
• multi-user?: yes
• sandbox: yes
• version: nix-env (Nix) 2.17.0
• nixpkgs: /etc/nix/inputs/nixpkgs

[Gerg-L]

Ideally, NIX_PROFILES would only include paths that exist in the first
place, but this is not the case. #241518 also seems related.

This isn't really possible with the current handling of NIX_PROFILES see this comment: #241518 (comment)

[tmuehlbacher]

This isn't really possible with the current handling of NIX_PROFILES see this comment: #241518 (comment)

👍 yes, I hope it didn't sound like I feel antagonistic to your PR, I really hope that it lands because I do enjoy a clean $HOME. 😄 I more wanted to show that my proposed solution is necessary because invalid paths in NIX_PROFILES are pretty much inevitable.

[jian-lin]

I cannot reproduce it.

Steps:

> echo $NIX_PROFILES
/run/current-system/sw /nix/var/nix/profiles/default /etc/profiles/per-user/me /home/me/.nix-profile

> rm -f ~/.nix-profile

> nix run github:NixOS/nixpkgs/ce5e4a6ef2e59d89a971bc434ca8ca222b9c7f5e#emacs29 -- -q --init-directory=/tmp/init-dir

> # exit Emacs

> file ~/.nix-profile
/home/me/.nix-profile: cannot open `/home/me/.nix-profile' (No such file or directory)

BTW, the value of native-comp-eln-load-path is ("/tmp/init-dir/eln-cache/" "/nix/store/hash-emacs-29.1-rc1/lib/emacs/29.1/native-lisp/"), which indicates another bug: adding NIX_PROFILES to native-comp-eln-load-path in site-start.el does not take effect.

[jian-lin]

BTW, the value of native-comp-eln-load-path is ("/tmp/init-dir/eln-cache/" "/nix/store/hash-emacs-29.1-rc1/lib/emacs/29.1/native-lisp/"), which indicates another bug: adding NIX_PROFILES to native-comp-eln-load-path in site-start.el does not take effect.

The bug I mention only happens in Emacs 29.

I can reproduce your issue in Emacs 28.

#251529 fixes this issue.

[tmuehlbacher]

I cannot reproduce it.

I'm sorry, I should have done more testing to isolate the issue. I tested out which of my packages is the culprit and the issue goes away if i remove this from my init.el:

(use-package ido-completing-read+
  :config
  (ido-ubiquitous-mode))

Maybe it has something to do with the ido-completing-read+ dependency memoize? (I am unfortunately not proficient enough with elisp to really be able to figure it out.)