From 6caac7345478e3d5f6aa25fe01d4075b53036b28 Mon Sep 17 00:00:00 2001
From: Sumit Solanki <sumit.solanki@ibm.com>
Date: Mon, 23 Mar 2026 15:52:10 +0530
Subject: [PATCH 1/2] fix(action): normalize EOF newline before kyaml parse in
 post-renderer pipeline Resolves: https://github.com/helm/helm/issues/31948

Signed-off-by: Sumit Solanki <sumit.solanki@ibm.com>
---
 pkg/action/action.go      | 15 +++++++++++++++
 pkg/action/action_test.go | 25 +++++++++++++++++++++++++
 2 files changed, 40 insertions(+)

diff --git a/pkg/action/action.go b/pkg/action/action.go
index 75b6cf8a0..6f71f4ff6 100644
--- a/pkg/action/action.go
+++ b/pkg/action/action.go
@@ -150,6 +150,19 @@ const (
 // "---apiVersion: v1" which is not a valid YAML document separator.
 // This function inserts a newline after any "---" at the start of a line
 // that is immediately followed by non-whitespace content.
+// ensureTrailingNewlineForYAML appends a final newline when the input omits one.
+// kyaml's reader does not add a trailing newline to the last YAML document when
+// splitting streams (see kio.ByteReader.Read); parsing and re-serializing then
+// rewrites literal block scalars from "|" to "|-" (strip chomping). A trailing
+// newline at EOF avoids that round-trip change so post-renderer merge/split
+// matches direct template output. See https://github.com/helm/helm/issues/31948
+func ensureTrailingNewlineForYAML(content string) string {
+	if content == "" || strings.HasSuffix(content, "\n") {
+		return content
+	}
+	return content + "\n"
+}
+
 func fixDocSeparators(content string) string {
 	var b strings.Builder
 	remaining := content
@@ -198,6 +211,7 @@ func annotateAndMerge(files map[string]string) (string, error) {
 		// separator. Insert the missing newline so kio.ParseAll can
 		// parse the content correctly.
 		content = fixDocSeparators(content)
+		content = ensureTrailingNewlineForYAML(content)
 
 		manifests, err := kio.ParseAll(content)
 		if err != nil {
@@ -221,6 +235,7 @@ func annotateAndMerge(files map[string]string) (string, error) {
 // splitAndDeannotate reconstructs individual files from a merged YAML stream,
 // removing filename annotations and grouping documents by their original filenames.
 func splitAndDeannotate(postrendered string) (map[string]string, error) {
+	postrendered = ensureTrailingNewlineForYAML(postrendered)
 	manifests, err := kio.ParseAll(postrendered)
 	if err != nil {
 		return nil, fmt.Errorf("error parsing YAML: %w", err)
diff --git a/pkg/action/action_test.go b/pkg/action/action_test.go
index 5271e34fa..6512aad8c 100644
--- a/pkg/action/action_test.go
+++ b/pkg/action/action_test.go
@@ -710,6 +710,31 @@ metadata:
 	}
 }
 
+// Regression: https://github.com/helm/helm/issues/31948 — kyaml parse/serialize
+// without a trailing newline rewrites "|" block scalars to "|-" unless we normalize EOF.
+func TestAnnotateAndMerge_PreservesLiteralBlockScalarWithoutEOFNewline(t *testing.T) {
+	files := map[string]string{
+		"templates/cm.yaml": `apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: test-config
+data:
+  value: |
+    my value
+    with multiple lines`,
+	}
+	merged, err := annotateAndMerge(files)
+	require.NoError(t, err)
+	assert.Contains(t, merged, "value: |")
+	assert.NotContains(t, merged, "value: |-")
+
+	reconstructed, err := splitAndDeannotate(merged)
+	require.NoError(t, err)
+	out := reconstructed["templates/cm.yaml"]
+	assert.Contains(t, out, "value: |")
+	assert.NotContains(t, out, "value: |-")
+}
+
 func TestSplitAndDeannotate(t *testing.T) {
 	tests := []struct {
 		name          string

From 58e71f16771381854aa79ce5cf392aa601a08da6 Mon Sep 17 00:00:00 2001
From: Sumit Solanki <sumit.solanki@ibm.com>
Date: Mon, 23 Mar 2026 16:22:55 +0530
Subject: [PATCH 2/2] Update pkg/action/action_test.go

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Signed-off-by: Sumit Solanki <sumit.solanki@ibm.com>
---
 pkg/action/action_test.go | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/pkg/action/action_test.go b/pkg/action/action_test.go
index 6512aad8c..447ee2598 100644
--- a/pkg/action/action_test.go
+++ b/pkg/action/action_test.go
@@ -728,11 +728,20 @@ data:
 	assert.Contains(t, merged, "value: |")
 	assert.NotContains(t, merged, "value: |-")
 
+	// Original behavior: splitAndDeannotate on the merged stream as produced.
 	reconstructed, err := splitAndDeannotate(merged)
 	require.NoError(t, err)
 	out := reconstructed["templates/cm.yaml"]
 	assert.Contains(t, out, "value: |")
 	assert.NotContains(t, out, "value: |-")
+
+	// New regression coverage: simulate a post-renderer output stream lacking a trailing newline.
+	mergedNoEOF := strings.TrimSuffix(merged, "\n")
+	reconstructedNoEOF, err := splitAndDeannotate(mergedNoEOF)
+	require.NoError(t, err)
+	outNoEOF := reconstructedNoEOF["templates/cm.yaml"]
+	assert.Contains(t, outNoEOF, "value: |")
+	assert.NotContains(t, outNoEOF, "value: |-")
 }
 
 func TestSplitAndDeannotate(t *testing.T) {