From 3d1091eb5b50667b71cd174b0beaadddceba2364 Mon Sep 17 00:00:00 2001
From: Aaron Andersen <aaron@fosslib.net>
Date: Tue, 28 Aug 2018 23:50:55 +0000
Subject: [PATCH] added a check to make sure a situation where a defined
 configuration wouldn't be unused as per recommended by @maurer

---
 nixos/modules/services/monitoring/incron.nix | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/nixos/modules/services/monitoring/incron.nix b/nixos/modules/services/monitoring/incron.nix
index edba38140c6c..c850bad881c4 100644
--- a/nixos/modules/services/monitoring/incron.nix
+++ b/nixos/modules/services/monitoring/incron.nix
@@ -59,6 +59,12 @@ in
 
   config = mkIf cfg.enable {
 
+    assertions = [
+      { assertion = cfg.allow != null -> cfg.deny == null;
+        message = "If `services.incron.allow` is set then `services.incron.deny` will be ignored.";
+      }
+    ];
+
     environment.systemPackages = [ pkgs.incron ];
 
     security.wrappers.incrontab.source = "${pkgs.incron}/bin/incrontab";