Add --allow-cluster-scoped flag whose default value is true (#95)

When the flag is set to false, this function should fail and return
a list of cluster-scoped resources.

functions/go/set-namespace/main.go

@@ -1,19 +1,25 @@
 package main
 
 import (
+	"fmt"
 	"os"
+	"strings"
 
 	"sigs.k8s.io/kustomize/kyaml/fn/framework"
 	"sigs.k8s.io/kustomize/kyaml/yaml"
 )
 
 var namespace string
+var allowClusterScoped bool
+
+var warning = "due to the difficulty of tracking all the cluster-scoped resource kinds, especially cluster-scoped CRDs."
 
 func main() {
 	resourceList := &framework.ResourceList{}
 	cmd := framework.Command(resourceList, func() error {
 		// cmd.Execute() will parse the ResourceList.functionConfig into cmd.Flags from
 		// the ResourceList.functionConfig.data field.
+		clusterScopedResources := []string{}
 		for i := range resourceList.Items {
 			// modify the resources using the kyaml/yaml library:
 			// https://pkg.go.dev/sigs.k8s.io/kustomize/kyaml/yaml
@@ -23,8 +29,9 @@ func main() {
 				// ignore the node if it does not have a "kind" field
 				continue
 			}
+			kind := yaml.GetValue(kindNode)
 			typeMeta := yaml.TypeMeta{
-				Kind: yaml.GetValue(kindNode),
+				Kind: kind,
 			}
 			if typeMeta.IsNamespaceable() {
 				// Set the metadata.namespace field
@@ -33,11 +40,35 @@ func main() {
 					yaml.FieldSetter{StringValue: namespace}); err != nil {
 					return err
 				}
+			} else {
+				if !allowClusterScoped {
+					apiVersionNode, err := node.Pipe(yaml.Lookup("apiVersion"))
+					if err != nil {
+						continue
+					}
+					apiVersion := yaml.GetValue(apiVersionNode)
+					nameNode, err := node.Pipe(yaml.Lookup("metadata", "name"))
+					if err != nil {
+						continue
+					}
+					name := yaml.GetValue(nameNode)
+					resID := fmt.Sprintf("apiVersion: %s, kind: %s, name: %s", apiVersion, kind, name)
+					clusterScopedResources = append(clusterScopedResources, resID)
+				}
 			}
 		}
+		if len(clusterScopedResources) > 0 {
+			return fmt.Errorf("the app config should only include namespace-scoped resources. "+
+				"But the following cluster-scoped resources are found:\n%s\n", strings.Join(clusterScopedResources, "\n"))
+		}
 		return nil
 	})
-	cmd.Flags().StringVar(&namespace, "namespace", "", "the namespace value")
+
+	cmd.Flags().BoolVar(&allowClusterScoped, "allow-cluster-scoped", true, "allow cluster-scoped resources or not. "+
+		"This function may not be able to identify all the cluster-scoped resources "+warning)
+	cmd.Flags().StringVar(&namespace, "namespace", "", "the namespace to be added into namespaced resources "+
+		"This function may set the metadata.namespace field of some cluster-scoped resources "+warning)
+
 	if err := cmd.Execute(); err != nil {
 		os.Exit(1)
 	}