From 9d94b98e46f8cf5f8abdcdc3cf0a271071922bc8 Mon Sep 17 00:00:00 2001
From: Finn Landweber <finn@landweber.xyz>
Date: Sat, 2 Mar 2024 12:25:00 +0100
Subject: [PATCH] nixos/borgmatic: refactor

added configuration check at built time
added borgmatic.enableConfigCheck whether or not it'll be executed.
---
 nixos/modules/services/backup/borgmatic.nix | 49 +++++++++++++--------
 1 file changed, 31 insertions(+), 18 deletions(-)

diff --git a/nixos/modules/services/backup/borgmatic.nix b/nixos/modules/services/backup/borgmatic.nix
index b27dd2817120..9cc0085c4c8a 100644
--- a/nixos/modules/services/backup/borgmatic.nix
+++ b/nixos/modules/services/backup/borgmatic.nix
@@ -76,29 +76,42 @@ in
       default = { };
       type = types.attrsOf cfgType;
     };
+
+    enableConfigCheck = mkEnableOption (lib.mdDoc "checking all configurations during build time") // { default = true; };
   };
 
-  config = mkIf cfg.enable {
+  config =
+    let
+      configFiles =
+        (optionalAttrs (cfg.settings != null) { "borgmatic/config.yaml".source = cfgfile; }) //
+        mapAttrs'
+          (name: value: nameValuePair
+            "borgmatic.d/${name}.yaml"
+            { source = settingsFormat.generate "${name}.yaml" value; })
+          cfg.configurations;
+      borgmaticCheck = name: f: pkgs.runCommandCC "${name} validation" { } ''
+            ${pkgs.borgmatic}/bin/borgmatic -c ${f.source} config validate
+            touch $out
+          '';
+    in
+      mkIf cfg.enable {
 
-    warnings = []
-      ++ optional (cfg.settings != null && cfg.settings ? location)
-        "`services.borgmatic.settings.location` is deprecated, please move your options out of sections to the global scope"
-      ++ optional (catAttrs "location" (attrValues cfg.configurations) != [])
-        "`services.borgmatic.configurations.<name>.location` is deprecated, please move your options out of sections to the global scope"
-    ;
+        warnings = []
+          ++ optional (cfg.settings != null && cfg.settings ? location)
+            "`services.borgmatic.settings.location` is deprecated, please move your options out of sections to the global scope"
+          ++ optional (catAttrs "location" (attrValues cfg.configurations) != [])
+            "`services.borgmatic.configurations.<name>.location` is deprecated, please move your options out of sections to the global scope"
+        ;
 
-    environment.systemPackages = [ pkgs.borgmatic ];
+        environment.systemPackages = [ pkgs.borgmatic ];
 
-    environment.etc = (optionalAttrs (cfg.settings != null) { "borgmatic/config.yaml".source = cfgfile; }) //
-      mapAttrs'
-        (name: value: nameValuePair
-          "borgmatic.d/${name}.yaml"
-          { source = settingsFormat.generate "${name}.yaml" value; })
-        cfg.configurations;
+        environment.etc = configFiles;
 
-    systemd.packages = [ pkgs.borgmatic ];
+        systemd.packages = [ pkgs.borgmatic ];
 
-    # Workaround: https://github.com/NixOS/nixpkgs/issues/81138
-    systemd.timers.borgmatic.wantedBy = [ "timers.target" ];
-  };
+        # Workaround: https://github.com/NixOS/nixpkgs/issues/81138
+        systemd.timers.borgmatic.wantedBy = [ "timers.target" ];
+
+        system.checks = mkIf cfg.enableConfigCheck (mapAttrsToList borgmaticCheck configFiles);
+      };
 }