nixos/prometheus/exporters: fix eval if only `openFirewall = true;` is set

If `openFirewall = true`, but no `firewallFilter` is set, the evaluation
fails with the following error:

    The option `services.prometheus.exporters.node.firewallFilter` is defined both null and
    not null, in `/home/ma27/Projects/nixpkgs/nixos/modules/services/monitoring/prometheus/exporters.nix'
    and `/home/ma27/Projects/nixpkgs/nixos/modules/services/monitoring/prometheus/exporters.nix'.

Originally introduced by me in #115185. The problem is that
`mkOptionDefault` has - as its name suggests - the same priority as the
default-value of the option `firewallFilter` and thus it conflicts if
this declaration and the actual default value are set which is the case
if `firewallFilter` isn't specified somewhere else.

1 files changed, 1 insertions, 1 deletions

diff --git a/nixos/modules/services/monitoring/prometheus/exporters.nix b/nixos/modules/services/monitoring/prometheus/exporters.nix
index 74ad4bf1837f5..5811cda11256b 100644
--- a/nixos/modules/services/monitoring/prometheus/exporters.nix
+++ b/nixos/modules/services/monitoring/prometheus/exporters.nix
@@ -131,7 +131,7 @@ let
           inherit name port;
         } // extraOpts);
       } ({ config, ... }: mkIf config.openFirewall {
-        firewallFilter = mkOptionDefault "-p tcp -m tcp --dport ${toString config.port}";
+        firewallFilter = mkDefault "-p tcp -m tcp --dport ${toString config.port}";
       })];
       internal = true;
       default = {};