From 2922dea563aaaf43a034a842cf5cbedcafb175d1 Mon Sep 17 00:00:00 2001
From: Winter <winter@winter.cafe>
Date: Mon, 20 Jul 2026 20:23:26 -0400
Subject: [PATCH] nixos/lib/testing: `builtins.length (lib.attrNames ...) > 0
 -> != to the empty set

(cherry picked from commit 244057cf9fe516aad51a689de8519daedf49dc97)
---
 nixos/lib/testing/run.nix | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/nixos/lib/testing/run.nix b/nixos/lib/testing/run.nix
index 0b35007f0c0b..b8a850489ffe 100644
--- a/nixos/lib/testing/run.nix
+++ b/nixos/lib/testing/run.nix
@@ -35,8 +35,7 @@ let
     options = {
       devnet = mkOption {
         type = types.bool;
-        default =
-          builtins.length (lib.attrNames containers) > 0 && builtins.length (lib.attrNames nodes) > 0;
+        default = containers != { } && nodes != { };
         defaultText = lib.literalMD "`true` if both VMs and containers are present.";
         description = ''
           This heuristic setting that assumes that the majority of tests requires VMs and containers
@@ -52,7 +51,7 @@ let
       };
       uid-range = mkOption {
         type = types.bool;
-        default = builtins.length (lib.attrNames containers) > 0;
+        default = containers != { };
         defaultText = lib.literalMD "`true` if containers are present.";
         description = "Containers use systemd-nspawn, which requires pid 0 inside of the sandbox. `uid-range` enables that.";
       };