{ config, lib, ... }:

let
  # Merge our session variable into any existing ones, if present.
  existingSessionVars = config.home.sessionVariables or {};
  sessionVars = existingSessionVars // {
    # Prepend snap desktop dir so snap-provided .desktop files are discovered by desktop environments.
    # We include `$XDG_DATA_DIRS` to preserve any previously-set value at runtime.
    XDG_DATA_DIRS = "/var/lib/snapd/desktop:$XDG_DATA_DIRS";
  };
in
{
  config = {
    # Use mkForce to ensure this module's value takes precedence when modules are merged.
    home.sessionVariables = lib.mkForce sessionVars;
  };
}