Add error message to parser for incorrectly configured subnets in connections

parsers/v1.nix

@@ -43,11 +43,13 @@ let
     
   /** getIpAddresses :: acl_peer -> acl_subnet -> [str] */
   getIpAddresses = acl_subnet: acl_peer: 
-    if (acl_peer.subnets."${acl_subnet.name}" ? ipAddresses) then (
-      if (elem "auto" acl_peer.subnets."${acl_subnet.name}".ipAddresses) then (
-        (remove "auto" acl_peer.subnets."${acl_subnet.name}".ipAddresses) ++ (singleton (generateIPv6Address acl_subnet.name acl_peer.name))
-      ) else acl_peer.subnets."${acl_subnet.name}".ipAddresses
-    ) else (singleton (generateIPv6Address acl_subnet.name acl_peer.name));
+    lib.throwIfNot (builtins.hasAttr acl_subnet.name acl_peer.subnets) "Tried getting the IP address for ${acl_peer.name} on subnet ${acl_subnet.name}. However, ${acl_peer.name} is not a member of ${acl_subnet.name}. It may be that you forgot to add ${acl_subnet.name} to `connections.*.subnets` in your ACL." (
+      if (acl_peer.subnets."${acl_subnet.name}" ? ipAddresses) then (
+        if (elem "auto" acl_peer.subnets."${acl_subnet.name}".ipAddresses) then (
+          (remove "auto" acl_peer.subnets."${acl_subnet.name}".ipAddresses) ++ (singleton (generateIPv6Address acl_subnet.name acl_peer.name))
+        ) else acl_peer.subnets."${acl_subnet.name}".ipAddresses
+      ) else (singleton (generateIPv6Address acl_subnet.name acl_peer.name))
+    );
   
   /** getPeerConnections :: acl_peer -> acl_subnet -> str -> peerConnection */
   getPeerConnections = acl_peerFrom: acl_subnet:
@@ -127,8 +129,8 @@ let
 
   subnetFromName = subnetName: findSingle
     (subnet: subnet.name == subnetName)
-    (throw "No subnet " + subnetName)
-    (throw "Multiply defined subnet " + subnetName)
+    (throw "No subnet " + subnetName + " when processing peer " + acl_peer)
+    (throw "Multiply defined subnet " + subnetName + " when processing peer " + acl_peer)
     v1_acl.subnets;