From b08b0bcbbec77046e5a7082177cedc12fbf1dc6c Mon Sep 17 00:00:00 2001
From: Robin Gloster <mail@glob.in>
Date: Wed, 25 Sep 2019 17:13:29 +0200
Subject: [PATCH] mkRemovedOptionModule: assert on removed options

We don't want to ignore config that can mess up machines. In general
this should always fail evaluation, as you think you are changing
behaviour and don't, which can easily create run-time errors we can
catch early.
---
 lib/modules.nix                                       | 11 +++++++----
 .../monitoring/prometheus/exporters/nginx.nix         |  2 +-
 nixos/modules/tasks/network-interfaces.nix            |  2 +-
 3 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/lib/modules.nix b/lib/modules.nix
index c3c903c1dfa8..00c7712487bd 100644
--- a/lib/modules.nix
+++ b/lib/modules.nix
@@ -592,11 +592,14 @@ rec {
     { options = setAttrByPath optionName (mkOption {
         visible = false;
       });
-      config.warnings =
-        let opt = getAttrFromPath optionName options; in
-        optional opt.isDefined ''
+      config.assertions =
+        let opt = getAttrFromPath optionName options; in [{
+          assertion = !opt.isDefined;
+          message = ''
             The option definition `${showOption optionName}' in ${showFiles opt.files} no longer has any effect; please remove it.
-            ${replacementInstructions}'';
+            ${replacementInstructions}
+          '';
+        }];
     };
 
   /* Return a module that causes a warning to be shown if the
diff --git a/nixos/modules/services/monitoring/prometheus/exporters/nginx.nix b/nixos/modules/services/monitoring/prometheus/exporters/nginx.nix
index 554377df37ba..ba852fea4336 100644
--- a/nixos/modules/services/monitoring/prometheus/exporters/nginx.nix
+++ b/nixos/modules/services/monitoring/prometheus/exporters/nginx.nix
@@ -49,6 +49,6 @@ in
     (mkRemovedOptionModule [ "insecure" ] ''
       This option was replaced by 'prometheus.exporters.nginx.sslVerify'.
     '')
-    ({ options.warnings = options.warnings; })
+    ({ options.warnings = options.warnings; options.assertions = options.assertions; })
   ];
 }
diff --git a/nixos/modules/tasks/network-interfaces.nix b/nixos/modules/tasks/network-interfaces.nix
index 5bf7b0d227f0..ee3ae2e91f20 100644
--- a/nixos/modules/tasks/network-interfaces.nix
+++ b/nixos/modules/tasks/network-interfaces.nix
@@ -305,7 +305,7 @@ let
             optional (defined ipv6Address && defined ipv6PrefixLength)
             { address = ipv6Address; prefixLength = ipv6PrefixLength; }))
 
-        ({ options.warnings = options.warnings; })
+        ({ options.warnings = options.warnings; options.assertions = options.assertions; })
       ];
 
   };