Fix silent failure of kustomize version with invalid output format

kustomize/commands/version/version.go

@@ -58,6 +58,9 @@ func (o *Options) Validate(_ []string) error {
 			return fmt.Errorf("--short and --output are mutually exclusive")
 		}
 	}
+	if o.Output != "" && o.Output != "yaml" && o.Output != "json" {
+		return fmt.Errorf("--output must be 'yaml' or 'json'")
+	}
 	return nil
 }
 

kustomize/commands/version/version_test.go

@@ -0,0 +1,33 @@
+// Copyright 2026 The Kubernetes Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+package version
+
+import (
+	"bytes"
+	"testing"
+)
+
+func TestVersionInvalidOutput(t *testing.T) {
+	var buf bytes.Buffer
+	cmd := NewCmdVersion(&buf)
+	cmd.SetArgs([]string{"--output", "yml"})
+	err := cmd.Execute()
+	if err == nil {
+		t.Fatalf("expected error for invalid output format, got nil")
+	}
+	expectedErr := "--output must be 'yaml' or 'json'"
+	if err.Error() != expectedErr {
+		t.Errorf("expected error %q, got %q", expectedErr, err.Error())
+	}
+}
+
+func TestVersionValidOutput(t *testing.T) {
+	var buf bytes.Buffer
+	cmd := NewCmdVersion(&buf)
+	cmd.SetArgs([]string{"--output", "yaml"})
+	err := cmd.Execute()
+	if err != nil {
+		t.Fatalf("unexpected error for valid output format: %v", err)
+	}
+}

plugin/builtin/prefixtransformer/PrefixTransformer.go

@@ -12,12 +12,14 @@ import (
 	"sigs.k8s.io/kustomize/api/types"
 	"sigs.k8s.io/kustomize/kyaml/resid"
 	"sigs.k8s.io/kustomize/kyaml/yaml"
+	"k8s.io/apimachinery/pkg/labels"
 )
 
 // Add the given prefix to the field
 type plugin struct {
-	Prefix     string        `json:"prefix,omitempty" yaml:"prefix,omitempty"`
-	FieldSpecs types.FsSlice `json:"fieldSpecs,omitempty" yaml:"fieldSpecs,omitempty"`
+	Prefix               string        `json:"prefix,omitempty" yaml:"prefix,omitempty"`
+	ExcludeLabelSelector string        `json:"excludeLabelSelector,omitempty" yaml:"excludeLabelSelector,omitempty"`
+	FieldSpecs           types.FsSlice `json:"fieldSpecs,omitempty" yaml:"fieldSpecs,omitempty"`
 }
 
 var KustomizePlugin plugin //nolint:gochecknoglobals
@@ -44,6 +46,14 @@ func (p *plugin) Config(
 }
 
 func (p *plugin) Transform(m resmap.ResMap) error {
+	var selector labels.Selector
+	if p.ExcludeLabelSelector != "" {
+		var err error
+		selector, err = labels.Parse(p.ExcludeLabelSelector)
+		if err != nil {
+			return err
+		}
+	}
 	// Even if the Prefix is empty we want to proceed with the
 	// transformation. This allows to add contextual information
 	// to the resources (AddNamePrefix).
@@ -52,6 +62,9 @@ func (p *plugin) Transform(m resmap.ResMap) error {
 		if p.shouldSkip(r.OrgId()) {
 			continue
 		}
+		if selector != nil && selector.Matches(labels.Set(r.GetLabels())) {
+			continue
+		}
 		id := r.OrgId()
 		// current default configuration contains
 		// only one entry: "metadata/name" with no GVK

plugin/builtin/suffixtransformer/SuffixTransformer.go

@@ -12,12 +12,14 @@ import (
 	"sigs.k8s.io/kustomize/api/types"
 	"sigs.k8s.io/kustomize/kyaml/resid"
 	"sigs.k8s.io/kustomize/kyaml/yaml"
+	"k8s.io/apimachinery/pkg/labels"
 )
 
 // Add the given suffix to the field
 type plugin struct {
-	Suffix     string        `json:"suffix,omitempty" yaml:"suffix,omitempty"`
-	FieldSpecs types.FsSlice `json:"fieldSpecs,omitempty" yaml:"fieldSpecs,omitempty"`
+	Suffix               string        `json:"suffix,omitempty" yaml:"suffix,omitempty"`
+	ExcludeLabelSelector string        `json:"excludeLabelSelector,omitempty" yaml:"excludeLabelSelector,omitempty"`
+	FieldSpecs           types.FsSlice `json:"fieldSpecs,omitempty" yaml:"fieldSpecs,omitempty"`
 }
 
 var KustomizePlugin plugin //nolint:gochecknoglobals
@@ -44,6 +46,14 @@ func (p *plugin) Config(
 }
 
 func (p *plugin) Transform(m resmap.ResMap) error {
+	var selector labels.Selector
+	if p.ExcludeLabelSelector != "" {
+		var err error
+		selector, err = labels.Parse(p.ExcludeLabelSelector)
+		if err != nil {
+			return err
+		}
+	}
 	// Even if the Suffix is empty we want to proceed with the
 	// transformation. This allows to add contextual information
 	// to the resources (AddNameSuffix).
@@ -52,6 +62,9 @@ func (p *plugin) Transform(m resmap.ResMap) error {
 		if p.shouldSkip(r.OrgId()) {
 			continue
 		}
+		if selector != nil && selector.Matches(labels.Set(r.GetLabels())) {
+			continue
+		}
 		id := r.OrgId()
 		// current default configuration contains
 		// only one entry: "metadata/name" with no GVK