deprecate some fn commands

cmd/config/internal/commands/cmdwrap.go

@@ -5,6 +5,7 @@ package commands
 
 import (
 	"bytes"
+	"fmt"
 	"io"
 	"os"
 	"path/filepath"
@@ -47,6 +48,7 @@ Environment Variables:
 
 `,
 		RunE:               r.runE,
+		PreRunE:            r.preRunE,
 		SilenceUsage:       true,
 		FParseErrWhitelist: cobra.FParseErrWhitelist{UnknownFlags: true},
 		Args:               cobra.MinimumNArgs(1),
@@ -78,6 +80,12 @@ func WrapCommand() *cobra.Command {
 	return GetWrapRunner().Command
 }
 
+func (r *WrapRunner) preRunE(_ *cobra.Command, _ []string) error {
+	_, err := fmt.Fprintln(os.Stderr, `Command "wrap" is deprecated, this will no longer be available in kustomize v5.
+See discussion in https://github.com/kubernetes-sigs/kustomize/issues/3953.`)
+	return err
+}
+
 func (r *WrapRunner) runE(c *cobra.Command, args []string) error {
 	if r.getEnv == nil {
 		r.getEnv = os.Getenv

cmd/config/internal/commands/cmdxargs.go

@@ -60,6 +60,7 @@ $ kyaml cat pkg/ --function-config config.yaml --wrap-kind ResourceList | kyaml
 
 `,
 		RunE:               r.runE,
+		PreRunE:            r.preRunE,
 		SilenceUsage:       true,
 		FParseErrWhitelist: cobra.FParseErrWhitelist{UnknownFlags: true},
 		Args:               cobra.MinimumNArgs(1),
@@ -84,6 +85,12 @@ func XArgsCommand() *cobra.Command {
 	return GetXArgsRunner().Command
 }
 
+func (r *XArgsRunner) preRunE(_ *cobra.Command, _ []string) error {
+	_, err := fmt.Fprintln(os.Stderr, `Command "xargs" is deprecated, this will no longer be available in kustomize v5.
+See discussion in https://github.com/kubernetes-sigs/kustomize/issues/3953.`)
+	return err
+}
+
 func (r *XArgsRunner) runE(c *cobra.Command, _ []string) error {
 	if len(r.Args) == 0 {
 		r.Args = os.Args

cmd/config/internal/commands/sink.go

@@ -4,6 +4,9 @@
 package commands
 
 import (
+	"fmt"
+	"os"
+
 	"github.com/spf13/cobra"
 	"sigs.k8s.io/kustomize/cmd/config/internal/generateddocs/commands"
 	"sigs.k8s.io/kustomize/cmd/config/runner"
@@ -20,6 +23,7 @@ func GetSinkRunner(name string) *SinkRunner {
 		Long:    commands.SinkLong,
 		Example: commands.SinkExamples,
 		RunE:    r.runE,
+		PreRunE: r.preRunE,
 		Args:    cobra.MaximumNArgs(1),
 	}
 	runner.FixDocs(name, c)
@@ -36,6 +40,12 @@ type SinkRunner struct {
 	Command *cobra.Command
 }
 
+func (r *SinkRunner) preRunE(c *cobra.Command, args []string) error {
+	_, err := fmt.Fprintln(os.Stderr, `Command "sink" is deprecated, this will no longer be available in kustomize v5.
+See discussion in https://github.com/kubernetes-sigs/kustomize/issues/3953.`)
+	return err
+}
+
 func (r *SinkRunner) runE(c *cobra.Command, args []string) error {
 	var outputs []kio.Writer
 	if len(args) == 1 {

cmd/config/internal/commands/source.go

@@ -5,6 +5,7 @@ package commands
 
 import (
 	"fmt"
+	"os"
 
 	"github.com/spf13/cobra"
 	"sigs.k8s.io/kustomize/cmd/config/internal/generateddocs/commands"
@@ -22,6 +23,7 @@ func GetSourceRunner(name string) *SourceRunner {
 		Long:    commands.SourceLong,
 		Example: commands.SourceExamples,
 		RunE:    r.runE,
+		PreRunE: r.preRunE,
 	}
 	runner.FixDocs(name, c)
 	c.Flags().StringVar(&r.WrapKind, "wrap-kind", kio.ResourceListKind,
@@ -47,6 +49,12 @@ type SourceRunner struct {
 	Command        *cobra.Command
 }
 
+func (r *SourceRunner) preRunE(c *cobra.Command, args []string) error {
+	_, err := fmt.Fprintln(os.Stderr, `Command "source" is deprecated, this will no longer be available in kustomize v5.
+See discussion in https://github.com/kubernetes-sigs/kustomize/issues/3953.`)
+	return err
+}
+
 func (r *SourceRunner) runE(c *cobra.Command, args []string) error {
 	// if there is a function-config specified, emit it
 	var functionConfig *yaml.RNode