Add enforcement message for apiVersion and kind

pkg/target/kusttarget.go

@@ -66,6 +66,13 @@ func NewKustTarget(
 		return nil, err
 	}
 	k.DealWithDeprecatedFields()
+	msgs, errs := k.EnforceFields()
+	if len(errs) > 0 {
+		return nil, fmt.Errorf(strings.Join(errs, "\n"))
+	}
+	if len(msgs) > 0 {
+		log.Printf(strings.Join(msgs, "\n"))
+	}
 	tConfig, err := makeTransformerConfig(ldr, k.Configurations)
 	if err != nil {
 		return nil, err

pkg/types/kustomization.go

@@ -21,6 +21,11 @@ import (
 	"sigs.k8s.io/kustomize/pkg/patch"
 )
 
+const (
+	KustomizationVersion = "v1"
+	KustomizationKind    = "Kustomization"
+)
+
 // TypeMeta copies apimachinery/pkg/apis/meta/v1.TypeMeta
 type TypeMeta struct {
 	// Kind copies apimachinery/pkg/apis/meta/v1.Typemeta.Kind
@@ -146,6 +151,21 @@ func (k *Kustomization) DealWithDeprecatedFields() {
 	}
 }
 
+func (k *Kustomization) EnforceFields() ([]string, []string) {
+	var msgs, errs []string
+	if k.APIVersion == "" {
+		msgs = append(msgs, "apiVersion is not defined. This will not be allowed in the next release.\nPlease add apiVersion: "+KustomizationVersion)
+	} else if k.APIVersion != KustomizationVersion {
+		errs = append(errs, "apiVersion should be "+KustomizationVersion)
+	}
+	if k.Kind == "" {
+		msgs = append(msgs, "kind is not defined. This will not be allowed in the next release.\nPlease add kind: "+KustomizationKind)
+	} else if k.Kind != KustomizationKind {
+		errs = append(errs, "kind should be "+KustomizationKind)
+	}
+	return msgs, errs
+}
+
 // GeneratorArgs contains arguments common to generators.
 type GeneratorArgs struct {
 	// Namespace for the configmap, optional