fix: route registry messages to stderr in template and show

When pulling an OCI chart, the registry client prints "Pulled: ..." and
"Digest: ..." status lines (and deprecation/underscore warnings) to its
configured output writer. Since v4.2.1 (introduced by #32056), these
messages leaked into the stdout output of helm template and helm show,
breaking downstream consumers such as cdk8s and other YAML parsers.

Fix by passing the command's stderr to the registry client in the
template and show commands instead of stdout. This keeps stdout clean
for machine-readable YAML while still surfacing registry warnings and
status messages on stderr for troubleshooting, rather than discarding
them. The pull/push commands continue to print these messages on their
normal output writer.

The show command's addRegistryClient writer parameter is renamed to
registryOut and wired through to the registry client, so it is no longer
a no-op.

Fixes #32215

Signed-off-by: Aaron Mark <64331623+amarkdotdev@users.noreply.github.com>

pkg/cmd/show.go

@@ -82,9 +82,9 @@ func newShowCmd(cfg *action.Configuration, out io.Writer) *cobra.Command {
 		Long:              showAllDesc,
 		Args:              require.ExactArgs(1),
 		ValidArgsFunction: validArgsFunc,
-		RunE: func(_ *cobra.Command, args []string) error {
+		RunE: func(cmd *cobra.Command, args []string) error {
 			client.OutputFormat = action.ShowAll
-			err := addRegistryClient(out, client)
+			err := addRegistryClient(cmd.ErrOrStderr(), client)
 			if err != nil {
 				return err
 			}
@@ -103,9 +103,9 @@ func newShowCmd(cfg *action.Configuration, out io.Writer) *cobra.Command {
 		Long:              showValuesDesc,
 		Args:              require.ExactArgs(1),
 		ValidArgsFunction: validArgsFunc,
-		RunE: func(_ *cobra.Command, args []string) error {
+		RunE: func(cmd *cobra.Command, args []string) error {
 			client.OutputFormat = action.ShowValues
-			err := addRegistryClient(out, client)
+			err := addRegistryClient(cmd.ErrOrStderr(), client)
 			if err != nil {
 				return err
 			}
@@ -124,9 +124,9 @@ func newShowCmd(cfg *action.Configuration, out io.Writer) *cobra.Command {
 		Long:              showChartDesc,
 		Args:              require.ExactArgs(1),
 		ValidArgsFunction: validArgsFunc,
-		RunE: func(_ *cobra.Command, args []string) error {
+		RunE: func(cmd *cobra.Command, args []string) error {
 			client.OutputFormat = action.ShowChart
-			err := addRegistryClient(out, client)
+			err := addRegistryClient(cmd.ErrOrStderr(), client)
 			if err != nil {
 				return err
 			}
@@ -145,9 +145,9 @@ func newShowCmd(cfg *action.Configuration, out io.Writer) *cobra.Command {
 		Long:              readmeChartDesc,
 		Args:              require.ExactArgs(1),
 		ValidArgsFunction: validArgsFunc,
-		RunE: func(_ *cobra.Command, args []string) error {
+		RunE: func(cmd *cobra.Command, args []string) error {
 			client.OutputFormat = action.ShowReadme
-			err := addRegistryClient(out, client)
+			err := addRegistryClient(cmd.ErrOrStderr(), client)
 			if err != nil {
 				return err
 			}
@@ -166,9 +166,9 @@ func newShowCmd(cfg *action.Configuration, out io.Writer) *cobra.Command {
 		Long:              showCRDsDesc,
 		Args:              require.ExactArgs(1),
 		ValidArgsFunction: validArgsFunc,
-		RunE: func(_ *cobra.Command, args []string) error {
+		RunE: func(cmd *cobra.Command, args []string) error {
 			client.OutputFormat = action.ShowCRDs
-			err := addRegistryClient(out, client)
+			err := addRegistryClient(cmd.ErrOrStderr(), client)
 			if err != nil {
 				return err
 			}
@@ -225,8 +225,8 @@ func runShow(args []string, client *action.Show) (string, error) {
 	return client.Run(cp)
 }
 
-func addRegistryClient(out io.Writer, client *action.Show) error {
-	registryClient, err := newRegistryClient(out, client.CertFile, client.KeyFile, client.CaFile,
+func addRegistryClient(registryOut io.Writer, client *action.Show) error {
+	registryClient, err := newRegistryClient(registryOut, client.CertFile, client.KeyFile, client.CaFile,
 		client.InsecureSkipTLSVerify, client.PlainHTTP, client.Username, client.Password)
 	if err != nil {
 		return fmt.Errorf("missing registry client: %w", err)

pkg/cmd/template.go

@@ -85,7 +85,7 @@ func newTemplateCmd(cfg *action.Configuration, out io.Writer) *cobra.Command {
 				client.KubeVersion = parsedKubeVersion
 			}
 
-			registryClient, err := newRegistryClient(out, client.CertFile, client.KeyFile, client.CaFile,
+			registryClient, err := newRegistryClient(cmd.ErrOrStderr(), client.CertFile, client.KeyFile, client.CaFile,
 				client.InsecureSkipTLSVerify, client.PlainHTTP, client.Username, client.Password)
 			if err != nil {
 				return fmt.Errorf("missing registry client: %w", err)