Require ListOptions when SkipOwnerReference is true

reconcilers/child.go

@@ -121,13 +121,19 @@ type ChildReconciler[Type, ChildType client.Object, ChildListType client.ObjectL
 	MergeBeforeUpdate func(current, desired ChildType)
 
 	// ListOptions allows custom options to be use when listing potential child resources. Each
-	// resource retrieved as part of the listing is confirmed via OurChild.
+	// resource retrieved as part of the listing is confirmed via OurChild. There is a performance
+	// benefit to limiting the number of resource return for each List operation, however,
+	// excluding an actual child will orphan that resource.
 	//
 	// Defaults to filtering by the reconciled resource's namespace:
 	//     []client.ListOption{
 	//         client.InNamespace(resource.GetNamespace()),
 	//     }
 	//
+	// ListOptions is required when a Finalizer is defined or SkipOwnerReference is true. An empty
+	// list is often sufficient although it may incur a performance penalty, especially when
+	// querying the API sever instead of an informer cache.
+	//
 	// +optional
 	ListOptions func(ctx context.Context, resource Type) []client.ListOption
 
@@ -229,6 +235,11 @@ func (r *ChildReconciler[T, CT, CLT]) validate(ctx context.Context) error {
 		return fmt.Errorf("ChildReconciler %q must implement OurChild since owner references are not used", r.Name)
 	}
 
+	if r.ListOptions == nil && r.SkipOwnerReference {
+		// ListOptions is required when SkipOwnerReference is true
+		return fmt.Errorf("ChildReconciler %q must implement ListOptions since owner references are not used", r.Name)
+	}
+
 	// require MergeBeforeUpdate
 	if r.MergeBeforeUpdate == nil {
 		return fmt.Errorf("ChildReconciler %q must implement MergeBeforeUpdate", r.Name)

reconcilers/childset.go

@@ -116,13 +116,19 @@ type ChildSetReconciler[Type, ChildType client.Object, ChildListType client.Obje
 	MergeBeforeUpdate func(current, desired ChildType)
 
 	// ListOptions allows custom options to be use when listing potential child resources. Each
-	// resource retrieved as part of the listing is confirmed via OurChild.
+	// resource retrieved as part of the listing is confirmed via OurChild. There is a performance
+	// benefit to limiting the number of resource return for each List operation, however,
+	// excluding an actual child will orphan that resource.
 	//
 	// Defaults to filtering by the reconciled resource's namespace:
 	//     []client.ListOption{
 	//         client.InNamespace(resource.GetNamespace()),
 	//     }
 	//
+	// ListOptions is required when a Finalizer is defined or SkipOwnerReference is true. An empty
+	// list is often sufficient although it may incur a performance penalty, especially when
+	// querying the API sever instead of an informer cache.
+	//
 	// +optional
 	ListOptions func(ctx context.Context, resource Type) []client.ListOption
 
@@ -257,6 +263,11 @@ func (r *ChildSetReconciler[T, CT, CLT]) validate(ctx context.Context) error {
 		return fmt.Errorf("ChildSetReconciler %q must implement OurChild since owner references are not used", r.Name)
 	}
 
+	if r.ListOptions == nil && r.SkipOwnerReference {
+		// ListOptions is required when SkipOwnerReference is true
+		return fmt.Errorf("ChildSetReconciler %q must implement ListOptions since owner references are not used", r.Name)
+	}
+
 	// require IdentifyChild
 	if r.IdentifyChild == nil {
 		return fmt.Errorf("ChildSetReconciler %q must implement IdentifyChild", r.Name)

reconcilers/validate_test.go

@@ -463,6 +463,22 @@ func TestChildReconciler_validate(t *testing.T) {
 				ListOptions:                func(ctx context.Context, parent *corev1.ConfigMap) []client.ListOption { return []client.ListOption{} },
 			},
 		},
+		{
+			name:   "ListOptions missing",
+			parent: &corev1.ConfigMap{},
+			reconciler: &ChildReconciler[*corev1.ConfigMap, *corev1.Pod, *corev1.PodList]{
+				Name:                       "ListOptions missing",
+				ChildType:                  &corev1.Pod{},
+				ChildListType:              &corev1.PodList{},
+				DesiredChild:               func(ctx context.Context, parent *corev1.ConfigMap) (*corev1.Pod, error) { return nil, nil },
+				ReflectChildStatusOnParent: func(ctx context.Context, parent *corev1.ConfigMap, child *corev1.Pod, err error) {},
+				MergeBeforeUpdate:          func(current, desired *corev1.Pod) {},
+				SkipOwnerReference:         true,
+				// ListOptions:                func(ctx context.Context, parent *corev1.ConfigMap) []client.ListOption { return []client.ListOption{} },
+				OurChild: func(resource *corev1.ConfigMap, child *corev1.Pod) bool { return true },
+			},
+			shouldErr: `ChildReconciler "ListOptions missing" must implement ListOptions since owner references are not used`,
+		},
 		{
 			name:   "Finalizer without OurChild",
 			parent: &corev1.ConfigMap{},
@@ -622,6 +638,23 @@ func TestChildSetReconciler_validate(t *testing.T) {
 				IdentifyChild:                 func(child *corev1.Pod) string { return "" },
 			},
 		},
+		{
+			name:   "ListOptions missing",
+			parent: &corev1.ConfigMap{},
+			reconciler: &ChildSetReconciler[*corev1.ConfigMap, *corev1.Pod, *corev1.PodList]{
+				Name:                          "ListOptions missing",
+				ChildType:                     &corev1.Pod{},
+				ChildListType:                 &corev1.PodList{},
+				DesiredChildren:               func(ctx context.Context, parent *corev1.ConfigMap) ([]*corev1.Pod, error) { return nil, nil },
+				ReflectChildrenStatusOnParent: func(ctx context.Context, parent *corev1.ConfigMap, result ChildSetResult[*corev1.Pod]) {},
+				MergeBeforeUpdate:             func(current, desired *corev1.Pod) {},
+				SkipOwnerReference:            true,
+				// ListOptions:                   func(ctx context.Context, parent *corev1.ConfigMap) []client.ListOption { return []client.ListOption{} },
+				OurChild:      func(resource *corev1.ConfigMap, child *corev1.Pod) bool { return true },
+				IdentifyChild: func(child *corev1.Pod) string { return "" },
+			},
+			shouldErr: `ChildSetReconciler "ListOptions missing" must implement ListOptions since owner references are not used`,
+		},
 		{
 			name:   "Finalizer without OurChild",
 			parent: &corev1.ConfigMap{},