man: System manpages have higher priority than user manpages

[MithicSpirit]

Describe the bug

/run/current-system/sw/share/man has higher priority than /etc/profiles/per-user/$USER/share/man because /run/wrappers/bin is earlier in the PATH, and it's set to /run/current-system/sw/share/man in the MANPATH_MAP.

Steps To Reproduce

Steps to reproduce the behavior:

1. Install packages with conlicting manpages on the system and the user (e.g., moreutils and parallel).
2. Try to open the manpage as the user (e.g., man parallel).
3. Manpage for package installed systemwide is opened.

Expected behavior

It should have opened the manpage for the one installed for the user, as that corresponds to the program that would be executed.

Additional context

I think that the easiest solution here is to remove the MANPATH_MAP entry for /run/wrappers/bin, though maybe this should be behind a setting (I could make a PR for this if desired). I think that ideally there would be a separate manpage collection just for wrappers, but I don't think this is feasible.

Note that this issue started with #65844.

Notify maintainers

@sternenseemann

Metadata

Please run nix-shell -p nix-info --run "nix-info -m" and paste the result.

[user@system:~]$ nix-shell -p nix-info --run "nix-info -m"
 - system: `"x86_64-linux"`
 - host os: `Linux 6.11.2-xanmod1, NixOS, 24.11 (Vicuna), 24.11.20241014.a3c0b3b`
 - multi-user?: `yes`
 - sandbox: `yes`
 - version: `nix-env (Nix) 2.24.9`
 - nixpkgs: `/nix/store/xnjw9gmfmpppdj6bxpw6cfkspc3h6xwl-source`

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[sternenseemann]

cc @matthewbauer

I think variants of this issue can't really be solved with how man-db works. Maybe we should move more of the configuration into the man-db nixos module, so it's easier for users to work around such problems.

[Aleksanaa]

What about just switching to environment variables?

[sternenseemann]

I think PATH has been preferred so far since it also works correctly-ish with nix-shell, see NixOS/nix#4702.