nixos/networking: Add a read-only option for the FQDN

This is a convenience option that can be used to quickly obtain the
configured FQDN.

1 files changed, 10 insertions, 4 deletions

diff --git a/nixos/tests/hostname.nix b/nixos/tests/hostname.nix
index 3b87303d73e74..8a77afc21733f 100644
--- a/nixos/tests/hostname.nix
+++ b/nixos/tests/hostname.nix
@@ -7,9 +7,12 @@ with import ../lib/testing-python.nix { inherit system pkgs; };
 with pkgs.lib;
 
 let
-  makeHostNameTest = hostName: domain:
+  makeHostNameTest = hostName: domain: fqdnOrNull:
     let
       fqdn = hostName + (optionalString (domain != null) ".${domain}");
+      getStr = str: # maybeString2String
+        let res = builtins.tryEval str;
+        in if (res.success && res.value != null) then res.value else "null";
     in
       makeTest {
         name = "hostname-${fqdn}";
@@ -26,13 +29,16 @@ let
           ];
         };
 
-        testScript = ''
+        testScript = { nodes, ... }: ''
           start_all()
 
           machine = ${hostName}
 
           machine.wait_for_unit("network-online.target")
 
+          # Test if NixOS computes the correct FQDN (either a FQDN or an error/null):
+          assert "${getStr nodes.machine.config.networking.fqdn}" == "${getStr fqdnOrNull}"
+
           # The FQDN, domain name, and hostname detection should work as expected:
           assert "${fqdn}" == machine.succeed("hostname --fqdn").strip()
           assert "${optionalString (domain != null) domain}" == machine.succeed("dnsdomainname").strip()
@@ -60,7 +66,7 @@ let
 
 in
 {
-  noExplicitDomain = makeHostNameTest "ahost" null;
+  noExplicitDomain = makeHostNameTest "ahost" null null;
 
-  explicitDomain = makeHostNameTest "ahost" "adomain";
+  explicitDomain = makeHostNameTest "ahost" "adomain" "ahost.adomain";
 }