fix(template): preserve manifest newlines across output modes

helm template trims the release manifest with TrimSpace, losing
intentional trailing newlines from its final document. Its hook,
--show-only and file writers can instead add an extra newline.

Keep the assembled output as []byte and write it directly, without
trimming. For hooks, selected manifests and output files, remove at most
one newline before the format string restores it. Each document stays
newline-terminated without adding or dropping authored blank lines.

Add golden-file coverage for stdout, --no-hooks, reordered --show-only
and --output-dir. A fixture chart covers zero, one and two trailing
newlines, including multiple regular and hook documents per file.

Signed-off-by: 胡玮文 <huweiwen.hww@alibaba-inc.com>

pkg/cmd/template.go

@@ -17,7 +17,6 @@ limitations under the License.
 package cmd
 
 import (
-	"bytes"
 	"errors"
 	"fmt"
 	"io"
@@ -118,8 +117,7 @@ func newTemplateCmd(cfg *action.Configuration, out io.Writer) *cobra.Command {
 			// We ignore a potential error here because, when the --debug flag was specified,
 			// we always want to print the YAML, even if it is not valid. The error is still returned afterwards.
 			if rel != nil {
-				var manifests bytes.Buffer
+				manifests := []byte(rel.Manifest)
-				fmt.Fprintln(&manifests, strings.TrimSpace(rel.Manifest))
 				if !client.DisableHooks {
 					fileWritten := make(map[string]bool)
 					for _, m := range rel.Hooks {
@@ -127,7 +125,7 @@ func newTemplateCmd(cfg *action.Configuration, out io.Writer) *cobra.Command {
 							continue
 						}
 						if client.OutputDir == "" {
-							fmt.Fprintf(&manifests, "---\n# Source: %s\n%s\n", m.Path, m.Manifest)
+							manifests = fmt.Appendf(manifests, "---\n# Source: %s\n%s\n", m.Path, strings.TrimSuffix(m.Manifest, "\n"))
 						} else {
 							newDir := client.OutputDir
 							if client.UseReleaseName {
@@ -151,7 +149,7 @@ func newTemplateCmd(cfg *action.Configuration, out io.Writer) *cobra.Command {
 				if len(showFiles) > 0 {
 					// This is necessary to ensure consistent manifest ordering when using --show-only
 					// with globs or directory names.
-					splitManifests := releaseutil.SplitManifests(manifests.String())
+					splitManifests := releaseutil.SplitManifests(string(manifests))
 					manifestsKeys := make([]string, 0, len(splitManifests))
 					for k := range splitManifests {
 						manifestsKeys = append(manifestsKeys, k)
@@ -195,10 +193,10 @@ func newTemplateCmd(cfg *action.Configuration, out io.Writer) *cobra.Command {
 						}
 					}
 					for _, m := range manifestsToRender {
-						fmt.Fprintf(out, "---\n%s\n", m)
+						fmt.Fprintf(out, "---\n%s\n", strings.TrimSuffix(m, "\n"))
 					}
 				} else {
-					fmt.Fprintf(out, "%s", manifests.String())
+					out.Write(manifests)
 				}
 			}
 
@@ -253,7 +251,7 @@ func writeToFile(outputDir, name, data string, appendData bool) error {
 
 	defer f.Close()
 
-	_, err = fmt.Fprintf(f, "---\n# Source: %s\n%s\n", name, data)
+	_, err = fmt.Fprintf(f, "---\n# Source: %s\n%s\n", name, strings.TrimSuffix(data, "\n"))
 	if err != nil {
 		return err
 	}

pkg/cmd/template_test.go

@@ -20,12 +20,17 @@ import (
 	"fmt"
 	"path/filepath"
 	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"helm.sh/helm/v4/internal/test"
 )
 
 var chartPath = "testdata/testcharts/subchart"
 
 func TestTemplateCmd(t *testing.T) {
 	deletevalchart := "testdata/testcharts/issue-9027"
+	newlinesChart := "testdata/testcharts/trailing-newlines"
 
 	tests := []cmdTestCase{
 		{
@@ -172,10 +177,66 @@ func TestTemplateCmd(t *testing.T) {
 			cmd:    fmt.Sprintf("template '%s' -f %s/extra_values.yaml", chartPath, chartPath),
 			golden: "output/template-subchart-cm-set-file.txt",
 		},
+		{
+			name:   "trailing newlines",
+			cmd:    fmt.Sprintf("template '%s'", newlinesChart),
+			golden: "output/template-newlines.txt",
+		},
+		{
+			name:   "trailing newlines without hooks",
+			cmd:    fmt.Sprintf("template '%s' --no-hooks", newlinesChart),
+			golden: "output/template-newlines-no-hooks.txt",
+		},
+		{
+			name:   "trailing newlines with reversed show-only order",
+			cmd:    fmt.Sprintf("template '%s' --show-only templates/hooks.yaml --show-only templates/00-no-newline-hook.yaml --show-only templates/regular.yaml --show-only templates/00-no-newline.yaml", newlinesChart),
+			golden: "output/template-newlines-reversed.txt",
+		},
+		{
+			name:   "trailing newlines with show-only regular manifests",
+			cmd:    fmt.Sprintf("template '%s' --show-only templates/regular.yaml", newlinesChart),
+			golden: "output/template-newlines-regular.txt",
+		},
+		{
+			name:   "trailing newlines with show-only hooks",
+			cmd:    fmt.Sprintf("template '%s' --show-only templates/hooks.yaml", newlinesChart),
+			golden: "output/template-newlines-hooks.txt",
+		},
+		{
+			name:   "missing final newline with show-only",
+			cmd:    fmt.Sprintf("template '%s' --show-only templates/00-no-newline.yaml", newlinesChart),
+			golden: "output/template-newlines-no-newline.txt",
+		},
+		{
+			name:   "missing final newline with show-only hook",
+			cmd:    fmt.Sprintf("template '%s' --show-only templates/00-no-newline-hook.yaml", newlinesChart),
+			golden: "output/template-newlines-no-newline-hook.txt",
+		},
 	}
 	runTestCmd(t, tests)
 }
 
+func TestTemplateCmdOutputDir(t *testing.T) {
+	t.Cleanup(resetEnv())
+	outputDir := t.TempDir()
+	_, _, err := executeActionCommand(fmt.Sprintf("template testdata/testcharts/trailing-newlines --output-dir %q", outputDir))
+	require.NoError(t, err)
+
+	for _, tc := range []struct {
+		file   string
+		golden string
+	}{
+		{"regular.yaml", "output/template-newlines-regular.txt"},
+		{"hooks.yaml", "output/template-newlines-hooks.txt"},
+		{"00-no-newline.yaml", "output/template-newlines-no-newline.txt"},
+		{"00-no-newline-hook.yaml", "output/template-newlines-no-newline-hook.txt"},
+	} {
+		t.Run(tc.file, func(t *testing.T) {
+			test.AssertGoldenFile(t, filepath.Join(outputDir, "trailing-newlines", "templates", tc.file), tc.golden)
+		})
+	}
+}
+
 func TestTemplateVersionCompletion(t *testing.T) {
 	repoFile := "testdata/helmhome/helm/repositories.yaml"
 	repoCache := "testdata/helmhome/helm/repository"

pkg/cmd/testdata/output/object-order.txt

@@ -202,4 +202,3 @@ spec:
     - Egress
     - Ingress
 
-

pkg/cmd/testdata/output/template-name-template.txt

@@ -93,7 +93,6 @@ metadata:
     "helm.sh/hook": test
 data:
   message: Hello World
-
 ---
 # Source: subchart/templates/tests/test-nothing.yaml
 apiVersion: v1
@@ -113,4 +112,3 @@ spec:
         - echo
         - "$message"
   restartPolicy: Never
-

pkg/cmd/testdata/output/template-newlines-hooks.txt

@@ -0,0 +1,25 @@
+---
+# Source: trailing-newlines/templates/hooks.yaml
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: hook-one-newline
+  annotations:
+    helm.sh/hook: pre-install
+data:
+  cfg: |+
+    line1
+    line2
+---
+# Source: trailing-newlines/templates/hooks.yaml
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: hook-two-newlines
+  annotations:
+    helm.sh/hook: pre-install
+data:
+  cfg: |+
+    line1
+    line2
+

pkg/cmd/testdata/output/template-newlines-no-hooks.txt

@@ -0,0 +1,31 @@
+---
+# Source: trailing-newlines/templates/00-no-newline.yaml
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: regular-no-newline
+data:
+  cfg: |+
+    line1
+    line2
+---
+# Source: trailing-newlines/templates/regular.yaml
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: regular-one-newline
+data:
+  cfg: |+
+    line1
+    line2
+---
+# Source: trailing-newlines/templates/regular.yaml
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: regular-two-newlines
+data:
+  cfg: |+
+    line1
+    line2
+

pkg/cmd/testdata/output/template-newlines-no-newline-hook.txt

@@ -0,0 +1,12 @@
+---
+# Source: trailing-newlines/templates/00-no-newline-hook.yaml
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: hook-no-newline
+  annotations:
+    helm.sh/hook: pre-install
+data:
+  cfg: |+
+    line1
+    line2

pkg/cmd/testdata/output/template-newlines-no-newline.txt

@@ -0,0 +1,10 @@
+---
+# Source: trailing-newlines/templates/00-no-newline.yaml
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: regular-no-newline
+data:
+  cfg: |+
+    line1
+    line2

pkg/cmd/testdata/output/template-newlines-regular.txt

@@ -0,0 +1,21 @@
+---
+# Source: trailing-newlines/templates/regular.yaml
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: regular-one-newline
+data:
+  cfg: |+
+    line1
+    line2
+---
+# Source: trailing-newlines/templates/regular.yaml
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: regular-two-newlines
+data:
+  cfg: |+
+    line1
+    line2
+

pkg/cmd/testdata/output/template-newlines-reversed.txt

@@ -0,0 +1,68 @@
+---
+# Source: trailing-newlines/templates/hooks.yaml
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: hook-one-newline
+  annotations:
+    helm.sh/hook: pre-install
+data:
+  cfg: |+
+    line1
+    line2
+---
+# Source: trailing-newlines/templates/hooks.yaml
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: hook-two-newlines
+  annotations:
+    helm.sh/hook: pre-install
+data:
+  cfg: |+
+    line1
+    line2
+
+---
+# Source: trailing-newlines/templates/00-no-newline-hook.yaml
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: hook-no-newline
+  annotations:
+    helm.sh/hook: pre-install
+data:
+  cfg: |+
+    line1
+    line2
+---
+# Source: trailing-newlines/templates/regular.yaml
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: regular-one-newline
+data:
+  cfg: |+
+    line1
+    line2
+---
+# Source: trailing-newlines/templates/regular.yaml
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: regular-two-newlines
+data:
+  cfg: |+
+    line1
+    line2
+
+---
+# Source: trailing-newlines/templates/00-no-newline.yaml
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: regular-no-newline
+data:
+  cfg: |+
+    line1
+    line2

pkg/cmd/testdata/output/template-newlines.txt

@@ -0,0 +1,68 @@
+---
+# Source: trailing-newlines/templates/00-no-newline.yaml
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: regular-no-newline
+data:
+  cfg: |+
+    line1
+    line2
+---
+# Source: trailing-newlines/templates/regular.yaml
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: regular-one-newline
+data:
+  cfg: |+
+    line1
+    line2
+---
+# Source: trailing-newlines/templates/regular.yaml
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: regular-two-newlines
+data:
+  cfg: |+
+    line1
+    line2
+
+---
+# Source: trailing-newlines/templates/00-no-newline-hook.yaml
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: hook-no-newline
+  annotations:
+    helm.sh/hook: pre-install
+data:
+  cfg: |+
+    line1
+    line2
+---
+# Source: trailing-newlines/templates/hooks.yaml
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: hook-one-newline
+  annotations:
+    helm.sh/hook: pre-install
+data:
+  cfg: |+
+    line1
+    line2
+---
+# Source: trailing-newlines/templates/hooks.yaml
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: hook-two-newlines
+  annotations:
+    helm.sh/hook: pre-install
+data:
+  cfg: |+
+    line1
+    line2
+

pkg/cmd/testdata/output/template-set.txt

@@ -93,7 +93,6 @@ metadata:
     "helm.sh/hook": test
 data:
   message: Hello World
-
 ---
 # Source: subchart/templates/tests/test-nothing.yaml
 apiVersion: v1
@@ -113,4 +112,3 @@ spec:
         - echo
         - "$message"
   restartPolicy: Never
-

pkg/cmd/testdata/output/template-show-only-glob.txt

@@ -8,7 +8,6 @@ rules:
 - apiGroups: [""]
   resources: ["pods"]
   verbs: ["get","list","watch"]
-
 ---
 # Source: subchart/templates/subdir/rolebinding.yaml
 apiVersion: rbac.authorization.k8s.io/v1
@@ -23,4 +22,3 @@ subjects:
 - kind: ServiceAccount
   name: subchart-sa
   namespace: default
-

pkg/cmd/testdata/output/template-show-only-multiple.txt

@@ -19,7 +19,6 @@ spec:
     name: nginx
   selector:
     app.kubernetes.io/name: subchart
-
 ---
 # Source: subchart/charts/subcharta/templates/service.yaml
 apiVersion: v1
@@ -37,4 +36,3 @@ spec:
     name: apache
   selector:
     app.kubernetes.io/name: subcharta
-

pkg/cmd/testdata/output/template-show-only-one.txt

@@ -19,4 +19,3 @@ spec:
     name: nginx
   selector:
     app.kubernetes.io/name: subchart
-

pkg/cmd/testdata/output/template-subchart-cm-set-file.txt

@@ -101,7 +101,6 @@ metadata:
     "helm.sh/hook": test
 data:
   message: Hello World
-
 ---
 # Source: subchart/templates/tests/test-nothing.yaml
 apiVersion: v1
@@ -121,4 +120,3 @@ spec:
         - echo
         - "$message"
   restartPolicy: Never
-

pkg/cmd/testdata/output/template-subchart-cm-set.txt

@@ -101,7 +101,6 @@ metadata:
     "helm.sh/hook": test
 data:
   message: Hello World
-
 ---
 # Source: subchart/templates/tests/test-nothing.yaml
 apiVersion: v1
@@ -121,4 +120,3 @@ spec:
         - echo
         - "$message"
   restartPolicy: Never
-

pkg/cmd/testdata/output/template-subchart-cm.txt

@@ -101,7 +101,6 @@ metadata:
     "helm.sh/hook": test
 data:
   message: Hello World
-
 ---
 # Source: subchart/templates/tests/test-nothing.yaml
 apiVersion: v1
@@ -121,4 +120,3 @@ spec:
         - echo
         - "$message"
   restartPolicy: Never
-

pkg/cmd/testdata/output/template-values-files.txt

@@ -93,7 +93,6 @@ metadata:
     "helm.sh/hook": test
 data:
   message: Hello World
-
 ---
 # Source: subchart/templates/tests/test-nothing.yaml
 apiVersion: v1
@@ -113,4 +112,3 @@ spec:
         - echo
         - "$message"
   restartPolicy: Never
-

pkg/cmd/testdata/output/template-with-api-version.txt

@@ -95,7 +95,6 @@ metadata:
     "helm.sh/hook": test
 data:
   message: Hello World
-
 ---
 # Source: subchart/templates/tests/test-nothing.yaml
 apiVersion: v1
@@ -115,4 +114,3 @@ spec:
         - echo
         - "$message"
   restartPolicy: Never
-

pkg/cmd/testdata/output/template-with-crds.txt

@@ -109,7 +109,6 @@ metadata:
     "helm.sh/hook": test
 data:
   message: Hello World
-
 ---
 # Source: subchart/templates/tests/test-nothing.yaml
 apiVersion: v1
@@ -129,4 +128,3 @@ spec:
         - echo
         - "$message"
   restartPolicy: Never
-

pkg/cmd/testdata/output/template-with-kube-version.txt

@@ -93,7 +93,6 @@ metadata:
     "helm.sh/hook": test
 data:
   message: Hello World
-
 ---
 # Source: subchart/templates/tests/test-nothing.yaml
 apiVersion: v1
@@ -113,4 +112,3 @@ spec:
         - echo
         - "$message"
   restartPolicy: Never
-

pkg/cmd/testdata/output/template.txt

@@ -93,7 +93,6 @@ metadata:
     "helm.sh/hook": test
 data:
   message: Hello World
-
 ---
 # Source: subchart/templates/tests/test-nothing.yaml
 apiVersion: v1
@@ -113,4 +112,3 @@ spec:
         - echo
         - "$message"
   restartPolicy: Never
-

pkg/cmd/testdata/testcharts/trailing-newlines/Chart.yaml

@@ -0,0 +1,3 @@
+apiVersion: v2
+name: trailing-newlines
+version: 0.1.0

pkg/cmd/testdata/testcharts/trailing-newlines/README.md

@@ -0,0 +1 @@
+The `00-no-newline*.yaml` templates intentionally have no final newline. The other templates contain two documents ending in one and two newlines, respectively. Keep chomping (`|+`) makes these newlines part of the ConfigMap value.

pkg/cmd/testdata/testcharts/trailing-newlines/templates/00-no-newline-hook.yaml

@@ -0,0 +1,10 @@
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: hook-no-newline
+  annotations:
+    helm.sh/hook: pre-install
+data:
+  cfg: |+
+    line1
+    line2

pkg/cmd/testdata/testcharts/trailing-newlines/templates/00-no-newline.yaml

@@ -0,0 +1,8 @@
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: regular-no-newline
+data:
+  cfg: |+
+    line1
+    line2

pkg/cmd/testdata/testcharts/trailing-newlines/templates/hooks.yaml

@@ -0,0 +1,22 @@
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: hook-one-newline
+  annotations:
+    helm.sh/hook: pre-install
+data:
+  cfg: |+
+    line1
+    line2
+---
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: hook-two-newlines
+  annotations:
+    helm.sh/hook: pre-install
+data:
+  cfg: |+
+    line1
+    line2
+

pkg/cmd/testdata/testcharts/trailing-newlines/templates/regular.yaml

@@ -0,0 +1,18 @@
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: regular-one-newline
+data:
+  cfg: |+
+    line1
+    line2
+---
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: regular-two-newlines
+data:
+  cfg: |+
+    line1
+    line2
+