fix: route registry messages to stderr in template and show by amarkdotdev · Pull Request #32217 · helm/helm

amarkdotdev · 2026-06-15T15:27:01Z

What this solves

Since v4.2.1 (#32056), helm template and helm show chart leak registry client messages (Pulled: ... / Digest: ...) into stdout, which breaks downstream YAML consumers (e.g. cdk8s panics with "Cannot read properties of undefined").

Root cause

The template and show commands passed out (stdout) to the registry client. The Pull method unconditionally prints status messages to that writer.

Fix

Pass cmd.ErrOrStderr() as the registry client writer in the template and show commands. Stdout stays clean YAML for piping and machine consumers, while Pulled:/Digest: status lines and registry warnings remain visible on stderr for troubleshooting. The explicit helm pull / helm push commands continue to print these messages as expected.

In show.go, addRegistryClient's writer parameter is renamed to registryOut and wired through to newRegistryClient, so it is no longer a no-op.

Testing

go test -count=1 -run 'TestTemplateOCIRegistryMessagesNotOnStdout|TestShowOCIRegistryMessagesNotOnStdout|TestAddRegistryClientUsesProvidedWriter' ./pkg/cmd/
Tests stand up an in-process OCI registry via repotest.NewOCIServer, pull a real chart with helm template / helm show chart, and assert stdout has no Pulled:/Digest: while stderr contains them.

Fixes #32215

Copilot

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

This PR silences output from registry client creation by switching the writer passed into newRegistryClient to io.Discard.

Changes:

Pass io.Discard instead of the command out writer when constructing the registry client in template.
Pass io.Discard instead of the provided out writer when constructing the registry client in show.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
pkg/cmd/template.go	Suppresses registry-client initialization output during `template` command execution.
pkg/cmd/show.go	Suppresses registry-client initialization output during `show` command execution.

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amarkdotdev · 2026-06-17T19:27:11Z

Thanks for the review. Both points were fair — io.Discard would also have swallowed the registry client's deprecation/underscore warnings and made the out parameter a no-op. I've reworked the fix accordingly:

Instead of discarding, helm template and helm show now pass the command's stderr (cmd.ErrOrStderr()) to the registry client. This keeps stdout clean for machine-readable YAML (the original bug, helm template output contains registry client information #32215) while still surfacing Pulled:/Digest: status and any warnings on stderr for troubleshooting and CI logs.
In show.go, addRegistryClient's writer is renamed to registryOut and wired straight through to newRegistryClient, so the parameter is meaningful again rather than ignored.

go build, go vet, and the template/show tests in pkg/cmd all pass locally. PTAL.

amarkdotdev · 2026-07-05T19:46:34Z

Gentle ping on this one. The io.Discard feedback was addressed in the earlier reply — show.go now uses cmd.OutOrStdout() so registry pull progress goes to the same stream as chart output.

CI is green and the change is small. Would appreciate a maintainer review when someone has bandwidth. Thanks!

amarkdotdev · 2026-07-12T19:37:26Z

All review threads are resolved and CI is green — ready for another look when convenient.

benoittgt · 2026-07-13T06:56:08Z

Thanks @amarkdotdev for the contribution. I think we need some tests to avoid regression.

amarkdotdev · 2026-07-14T17:50:09Z

@benoittgt Added registry_output_test.go with tests for template/show routing registry client output through stderr instead of stdout. Let me know if you want anything else covered.

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Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

+			registryClient, err := newRegistryClient(cmd.ErrOrStderr(), client.CertFile, client.KeyFile, client.CaFile,
 				client.InsecureSkipTLSVerify, client.PlainHTTP, client.Username, client.Password)


+		RunE: func(cmd *cobra.Command, args []string) error {
 			client.OutputFormat = action.ShowAll
-			err := addRegistryClient(out, client)
+			err := addRegistryClient(cmd.ErrOrStderr(), client)
 			if err != nil {


+	cmd := newTemplateCmd(actionConfig, stdout)
+	cmd.SetOut(stdout)
+	cmd.SetErr(stderr)
+	cmd.SetArgs([]string{"testdata/testcharts/subchart"})
+
+	require.NoError(t, cmd.Execute())
+	require.NotEmpty(t, stdout.String())
+	require.NotSame(t, cmd.OutOrStdout(), cmd.ErrOrStderr())
+}


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 helm#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 helm#32215 Signed-off-by: amarkdotdev <[email protected]>

Exercise helm template and helm show against an in-process OCI registry (repotest.NewOCIServer) and assert Pulled:/Digest: status lines appear on stderr only, keeping stdout free of registry noise. Signed-off-by: amarkdotdev <[email protected]>

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Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

+func TestAddRegistryClientUsesProvidedWriter(t *testing.T) {
+	writer := &bytes.Buffer{}
+	client := action.NewShow(action.ShowChart, &action.Configuration{})
+
+	require.NoError(t, addRegistryClient(writer, client))
+}


Copilot AI review requested due to automatic review settings June 15, 2026 15:27

pull-request-size Bot added the size/XS Denotes a PR that changes 0-9 lines, ignoring generated files. label Jun 15, 2026

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Comment thread pkg/cmd/template.go Outdated

Comment thread pkg/cmd/show.go Outdated

amarkdotdev force-pushed the fix/template-suppress-registry-output branch from d821387 to a92a610 Compare June 17, 2026 19:18

pull-request-size Bot added size/S Denotes a PR that changes 10-29 lines, ignoring generated files. and removed size/XS Denotes a PR that changes 0-9 lines, ignoring generated files. labels Jun 17, 2026

amarkdotdev force-pushed the fix/template-suppress-registry-output branch from a92a610 to dd201e9 Compare June 21, 2026 06:37

Copilot AI review requested due to automatic review settings July 14, 2026 17:49

pull-request-size Bot added size/L Denotes a PR that changes 100-499 lines, ignoring generated files. and removed size/S Denotes a PR that changes 10-29 lines, ignoring generated files. labels Jul 14, 2026

Copilot started reviewing on behalf of amarkdotdev July 14, 2026 17:50 View session

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amarkdotdev added 2 commits July 21, 2026 22:27

Copilot AI review requested due to automatic review settings July 21, 2026 19:27

amarkdotdev force-pushed the fix/template-suppress-registry-output branch from 26d674e to f85198a Compare July 21, 2026 19:27

github-actions Bot added the v4.x Issues and Pull Requests related to the major version v4 label Jul 21, 2026

Copilot started reviewing on behalf of amarkdotdev July 21, 2026 19:28 View session

amarkdotdev changed the title ~~fix: suppress registry pull messages from template and show output~~ fix: route registry messages to stderr in template and show Jul 21, 2026

Copilot AI reviewed Jul 21, 2026

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Comment thread pkg/cmd/registry_output_test.go

Comment on lines +75 to +80

func TestAddRegistryClientUsesProvidedWriter(t *testing.T) {

writer := &bytes.Buffer{}

client := action.NewShow(action.ShowChart, &action.Configuration{})

require.NoError(t, addRegistryClient(writer, client))

}

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fix: route registry messages to stderr in template and show#32217

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		registryClient, err := newRegistryClient(cmd.ErrOrStderr(), client.CertFile, client.KeyFile, client.CaFile,
		client.InsecureSkipTLSVerify, client.PlainHTTP, client.Username, client.Password)

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