bug: dconf.enable breaks gvfs (and probably more) on NixOS

[keysmashes]

Are you following the right branch?

• My Nixpkgs and Home Manager versions are in sync

Is there an existing issue for this?

• I have searched the existing issues

Issue description

Since #7021, if Home Manager's dconf.enable is set (i.e. on all non-Darwin platforms), then $GIO_EXTRA_MODULES is set via home.sessionVariables. However, NixOS also likes to set $GIO_EXTRA_MODULES, for example when NixOS services.gvfs.enable is set.

This means that Home Manager overrides the environment variable set by NixOS (rather than extending it), which breaks things like "mounting remote filesystems in thunar".

Maintainer CC

@Rosuavio @rycee

System information

- system: `"x86_64-linux"`
 - host os: `Linux 6.12.30, NixOS, 25.11 (Xantusia), 25.11.20250523.063f43f`
 - multi-user?: `yes`
 - sandbox: `yes`
 - version: `nix-env (Lix, like Nix) 2.93.0
System type: x86_64-linux
Additional system types: i686-linux, x86_64-v1-linux, x86_64-v2-linux, x86_64-v3-linux
Features: gc, signed-caches
System configuration file: /etc/nix/nix.conf
User configuration files: /home/ash/.config/nix/nix.conf:/etc/xdg/nix/nix.conf:/home/ash/.nix-profile/etc/xdg/nix/nix.conf:/nix/profile/etc/xdg/nix/nix.conf:/home/ash/.local/state/nix/profile/etc/xdg/nix/nix.conf:/etc/profiles/per-user/ash/etc/xdg/nix/nix.conf:/nix/var/nix/profiles/default/etc/xdg/nix/nix.conf:/run/current-system/sw/etc/xdg/nix/nix.conf
Store directory: /nix/store
State directory: /nix/var/nix
Data directory: /nix/store/7wv7x01fjp05n40yb263wlrm0hvhzbyn-lix-2.93.0/share`
 - nixpkgs: `/etc/nixpkgs/channels/nixpkgs`

[Rosuavio]

Thanks @keysmashes for point this out. I was going make a PR to just remove the GIO line, but #7146 seems like it is a better fix.