From 250885d0caed9ab910e801d7a3c21d6f83d4cdae Mon Sep 17 00:00:00 2001
From: Matthew Bauer <mjbauer95@gmail.com>
Date: Mon, 6 Jul 2020 01:48:19 -0400
Subject: [PATCH] nixos/nix-daemon.nix: assert distributedBuilds and
 buildMachines!=[]
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Without distributedBuilds, you can’t use buildMachines flag.

Fixes #56593
---
 nixos/modules/services/misc/nix-daemon.nix | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/nixos/modules/services/misc/nix-daemon.nix b/nixos/modules/services/misc/nix-daemon.nix
index 0b3d7f3f03c3..8441b063e966 100644
--- a/nixos/modules/services/misc/nix-daemon.nix
+++ b/nixos/modules/services/misc/nix-daemon.nix
@@ -439,6 +439,13 @@ in
 
   config = {
 
+    assertions = [
+      {
+        assertion = (!config.nix.distributedBuilds) && config.nix.buildMachines != [];
+        message = "You must set `nix.distributedBuilds = true` to use nix.buildMachines";
+      }
+    ];
+
     nix.binaryCachePublicKeys = [ "cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY=" ];
     nix.binaryCaches = [ "https://cache.nixos.org/" ];