xdg-portal: update env vars, match nixos module

[Misterio77]

Description

Nixpkgs has recently(ish) made a few major changes to its xdg-desktop-portal package (NixOS/nixpkgs#268197), which silently breaks our module here:

• The NIXOS_XDG_DESKTOP_PORTAL_CONFIG_DIR variable patch has been removed (in favor of putting portal configurations in /etc or XDG_CONFIG_HOME).
• A new variable, NIX_XDG_DESKTOP_PORTAL_DIR, was introduced in a patch to avoid setting XDG_DESKTOP_PORTAL_DIR (which also affected portal configuration reading, not only portal definitions)

I updated our module to match the changes, but this breakage also made me revisit this module and look into some improvements.

Long story short, I think it's worth it to make it more similar to the NixOS one, as it will make behavior more predictable and consistent.

The main change is relying on the upstream linked systemd unit (instead of using systemd.user.services), and setting the environment variables globally instead of scoping it to the unit, as it's a very global thing anyway.

This might not be backwards compatible for people already facing #4922/#4972. Maybe I should also provide the unit to ~/.config?

Checklist

• Change is backwards compatible.

• Code formatted with ./format.

• Code tested through nix-shell --pure tests -A run.all or nix develop --ignore-environment .#all using Flakes.

• Test cases updated/added. See example.

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Maintainer CC

[rycee]

Thanks! Merged to master now 🙂

[andresilva]

This broke portals for me.

❯ ls $NIX_XDG_DESKTOP_PORTAL_DIR
"/etc/profiles/per-user/andre/share/xdg-desktop-portal/portals": No such file or directory (os error 2)

Is this expected? The test passes though and it is expecting the correct output, so not really sure what's happening with my setup, my config is very much the same as the one in the test except I don't have any config (just a single entry configPackages).

Edit: for reasons that I am failing to understand /share/xdg-desktop-portal from the portals packages isn't getting linked into home.path, even though all the other files from the package are.

Edit2: environment.pathsToLink = [ "/share/xdg-desktop-portal" "/share/applications" ]; needs to be set. The tests pass because they're testing against home-manager-path directly.

[Misterio77]

Hey @andresilva,

I can reproduce your issue when using the NixOS module and useUserPackages set to true, as in this case only specific stuff will get linked (as opposed to the entire home-manager-path being linked). For this, users will have to set environment.pathsToLink, as you noted.

I will open a follow up PR adding this info to the manual, similarly to programs.bash.enableCompletion.

[Misterio77]

Alternatively, I wonder if the module could perhaps provide a sane pathsToLink default? Maybe conditionally?

Also, #2548 possibly fixes this, too.

[Misterio77]

Note added in #5184

[bobvanderlinden]

I ran into issues with this solution. Somehow /etc/profiles/per-user/bob.vanderlinden/share/xdg-desktop-portal/ didn't exist. Adding extraPortals to home.packages also did not work to get share/xdg-desktop-portal.

A solution that did work was to explicitly set NIX_XDG_DESKTOP_PORTAL_DIR to a symlinkJoin path of the extraPortals packages:

          home.sessionVariables.NIX_XDG_DESKTOP_PORTAL_DIR = lib.mkForce
            (let
              root = pkgs.symlinkJoin {
                name = "root";
                paths = config.xdg.portal.extraPortals;
              };
            in
              "${root}/share/xdg-desktop-portal/portals"
            );
          systemd.user.sessionVariables.NIX_XDG_DESKTOP_PORTAL_DIR = lib.mkForce config.home.sessionVariables.NIX_XDG_DESKTOP_PORTAL_DIR;

Would this be an viable solution to adopt in home-manager?

[Misterio77]

Hey @bobvanderlinden,

I went with the profile approach as it is more consistent with the NixOS module, and relying on these nixpkgs-specific variables is a little risky, in my opinion (as this PR was written to fix breakage caused by NIXOS_XDG_DESKTOP_PORTAL_CONFIG_DIR being removed).

The issue you're facing, I believe, only happens if you're running NixOS and have useUserPackages = true, which links a lot less stuff. In that case, you should set pathsToLink like so:

environment.pathsToLink = [ "/share/xdg-desktop-portal" ];

See #5184