fix ConfigMap data with leading underscore (hall#44)

modules/k8s.nix

@@ -16,12 +16,24 @@ with lib; let
       )
       cfg.api.defaults);
 
-  moduleToAttrs = value:
-    if isAttrs value
-    then mapAttrs (_n: moduleToAttrs) (filterAttrs (n: v: v != null && !(hasPrefix "_" n)) value)
-    else if isList value
-    then map moduleToAttrs value
-    else value;
+  moduleToAttrs = objType: propertyPath: value:
+    if isAttrs value then
+      let
+        # Fix https://github.com/hall/kubenix/issues/44
+        # The check for names starting with leading '_' has been here since forever.
+        # Not sure where it makes sense, but it definitely doesn't make sense for ConfigMap -> data/binaryData
+        # => To get a minimal invasive fix we added `objType` and `propertyPath` to make `moduleToAttrs` "context-aware".
+        #    This way we can allow names with leading underscore exactly for ConfigMap -> data/binaryData 
+        allowLeadingUnderscore = objType.group == "core" && objType.version == "v1" && objType.kind == "ConfigMap" &&
+          (propertyPath == [ "data" ] || propertyPath == [ "binaryData" ]);
+        filterName = name: allowLeadingUnderscore || !(hasPrefix "_" name);
+        filteredAttrs = filterAttrs (n: v: v != null && filterName n) value;
+      in
+      mapAttrs (_n: moduleToAttrs objType (propertyPath ++ [ _n ])) filteredAttrs
+    else if isList value then
+      map (moduleToAttrs objType propertyPath) value
+    else
+      value;
 
   apiOptions = { config, ... }: {
     options = {
@@ -536,7 +548,7 @@ in
 
     kubernetes.objects = flatten (mapAttrsToList
       (_: type:
-        mapAttrsToList (_name: moduleToAttrs)
+        mapAttrsToList (_name: moduleToAttrs type [ ])
           (optionalHashedNames' cfg.api.resources.${type.group}.${type.version}.${type.kind} type.kind)
       )
       cfg.api.types);

tests/default.nix

@@ -21,6 +21,7 @@ let
             ./k8s/defaults.nix
             ./k8s/order.nix
             ./k8s/submodule.nix
+            ./k8s/configmap.nix
             # TODO: `importYaml` uses IFD which fails during `nix flake check` as it evaluates
             # for all systems, not only the current one: https://github.com/hall/kubenix/issues/12
             # ./k8s/imports.nix

tests/k8s/configmap.nix

@@ -0,0 +1,20 @@
+{ config, kubenix, ... }:
+let
+  configMapData = (builtins.head config.kubernetes.objects).data;
+in
+{
+  imports = [ kubenix.modules.test kubenix.modules.k8s ];
+
+  test = {
+    name = "k8s-simple";
+    description = "Test that ConfigMap data keys can have a leading underscore (https://github.com/hall/kubenix/issues/44)";
+    assertions = [
+      {
+        message = "leading underscore in ConfigMap key should be preserved";
+        assertion = configMapData == { _FOO = "_bar"; };
+      }
+    ];
+  };
+
+  kubernetes.resources.configMaps.foo.data._FOO = "_bar";
+}