fix: insert newline after doc separators glued to content by template trimming

Signed-off-by: Matheus Pimenta <matheuscscp@gmail.com>

pkg/action/action.go

@@ -144,6 +144,39 @@ const (
 	filenameAnnotation = "postrenderer.helm.sh/postrender-filename"
 )
 
+// fixDocSeparators ensures YAML document separators ("---") are always
+// followed by a newline in rendered template content. Go template whitespace
+// trimming ({{-) can remove the newline after "---", producing e.g.
+// "---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.
+func fixDocSeparators(content string) string {
+	var b strings.Builder
+	remaining := content
+	for {
+		// Find "---" at the start of a line (or start of content).
+		idx := strings.Index(remaining, "---")
+		if idx == -1 {
+			b.WriteString(remaining)
+			break
+		}
+		// "---" must be at the start of a line: either idx==0 or preceded by '\n'.
+		if idx > 0 && remaining[idx-1] != '\n' {
+			b.WriteString(remaining[:idx+3])
+			remaining = remaining[idx+3:]
+			continue
+		}
+		b.WriteString(remaining[:idx+3])
+		remaining = remaining[idx+3:]
+		// If "---" is followed by non-whitespace (e.g. "---apiVersion"),
+		// insert a newline to make it a proper document separator.
+		if len(remaining) > 0 && remaining[0] != '\n' && remaining[0] != '\r' && remaining[0] != ' ' && remaining[0] != '\t' {
+			b.WriteByte('\n')
+		}
+	}
+	return b.String()
+}
+
 // annotateAndMerge combines multiple YAML files into a single stream of documents,
 // adding filename annotations to each document for later reconstruction.
 func annotateAndMerge(files map[string]string) (string, error) {
@@ -159,6 +192,13 @@ func annotateAndMerge(files map[string]string) (string, error) {
 			continue
 		}
 
+		// Fix document separators where Go template whitespace trimming
+		// ({{-) has removed the newline after "---", producing e.g.
+		// "---apiVersion: v1" which is not a valid YAML document
+		// separator. Insert the missing newline so kio.ParseAll can
+		// parse the content correctly.
+		content = fixDocSeparators(content)
+
 		manifests, err := kio.ParseAll(content)
 		if err != nil {
 			return "", fmt.Errorf("parsing %s: %w", fname, err)

pkg/action/action_test.go

@@ -403,6 +403,96 @@ func (m *mockPostRenderer) Run(renderedManifests *bytes.Buffer) (*bytes.Buffer,
 	return bytes.NewBufferString(content), nil
 }
 
+func TestFixDocSeparators(t *testing.T) {
+	tests := []struct {
+		name     string
+		input    string
+		expected string
+	}{
+		{
+			name:     "no separator",
+			input:    "apiVersion: v1\nkind: Service\n",
+			expected: "apiVersion: v1\nkind: Service\n",
+		},
+		{
+			name:     "separator on its own line",
+			input:    "---\napiVersion: v1\nkind: Service\n",
+			expected: "---\napiVersion: v1\nkind: Service\n",
+		},
+		{
+			name:     "leading separator glued to content",
+			input:    "---apiVersion: v1\nkind: Service\n",
+			expected: "---\napiVersion: v1\nkind: Service\n",
+		},
+		{
+			name:     "mid-content separator glued to content",
+			input:    "apiVersion: v1\nkind: ConfigMap\n---apiVersion: v1\nkind: Service\n",
+			expected: "apiVersion: v1\nkind: ConfigMap\n---\napiVersion: v1\nkind: Service\n",
+		},
+		{
+			name:     "multiple separators all proper",
+			input:    "---\napiVersion: v1\n---\napiVersion: v1\n",
+			expected: "---\napiVersion: v1\n---\napiVersion: v1\n",
+		},
+		{
+			name:     "multiple separators some glued",
+			input:    "---apiVersion: v1\nkind: ConfigMap\n---apiVersion: v1\nkind: Service\n",
+			expected: "---\napiVersion: v1\nkind: ConfigMap\n---\napiVersion: v1\nkind: Service\n",
+		},
+		{
+			name:     "empty string",
+			input:    "",
+			expected: "",
+		},
+		{
+			name:     "only separator",
+			input:    "---\n",
+			expected: "---\n",
+		},
+		{
+			name:     "triple dash in a value is not a separator",
+			input:    "data:\n  key: ---value\n",
+			expected: "data:\n  key: ---value\n",
+		},
+		{
+			name:     "realistic multi-doc template output",
+			input:    "apiVersion: v1\nkind: Deployment\n---\napiVersion: v1\nkind: Ingress\n---apiVersion: v1\nkind: Service\n",
+			expected: "apiVersion: v1\nkind: Deployment\n---\napiVersion: v1\nkind: Ingress\n---\napiVersion: v1\nkind: Service\n",
+		},
+		{
+			name:     "separator followed by carriage return",
+			input:    "---\r\napiVersion: v1\n",
+			expected: "---\r\napiVersion: v1\n",
+		},
+		{
+			name:     "separator followed by space",
+			input:    "--- \napiVersion: v1\n",
+			expected: "--- \napiVersion: v1\n",
+		},
+		{
+			name:     "separator followed by tab",
+			input:    "---\t\napiVersion: v1\n",
+			expected: "---\t\napiVersion: v1\n",
+		},
+		{
+			name:     "four dashes on its own line",
+			input:    "----\napiVersion: v1\n",
+			expected: "---\n-\napiVersion: v1\n",
+		},
+		{
+			name:     "four dashes followed by text",
+			input:    "----more\napiVersion: v1\n",
+			expected: "---\n-more\napiVersion: v1\n",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			assert.Equal(t, tt.expected, fixDocSeparators(tt.input))
+		})
+	}
+}
+
 func TestAnnotateAndMerge(t *testing.T) {
 	tests := []struct {
 		name          string
@@ -543,6 +633,65 @@ metadata:
 			},
 			expectedError: "parsing templates/invalid.yaml",
 		},
+		{
+			name: "leading doc separator glued to content by template whitespace trimming",
+			files: map[string]string{
+				"templates/service.yaml": "---apiVersion: v1\nkind: Service\nmetadata:\n  name: test-svc\n",
+			},
+			expected: `apiVersion: v1
+kind: Service
+metadata:
+  name: test-svc
+  annotations:
+    postrenderer.helm.sh/postrender-filename: 'templates/service.yaml'
+`,
+		},
+		{
+			name: "leading doc separator on its own line",
+			files: map[string]string{
+				"templates/service.yaml": "---\napiVersion: v1\nkind: Service\nmetadata:\n  name: test-svc\n",
+			},
+			expected: `apiVersion: v1
+kind: Service
+metadata:
+  name: test-svc
+  annotations:
+    postrenderer.helm.sh/postrender-filename: 'templates/service.yaml'
+`,
+		},
+		{
+			name: "multiple leading doc separators",
+			files: map[string]string{
+				"templates/service.yaml": "---\n---\napiVersion: v1\nkind: Service\nmetadata:\n  name: test-svc\n",
+			},
+			expected: `apiVersion: v1
+kind: Service
+metadata:
+  name: test-svc
+  annotations:
+    postrenderer.helm.sh/postrender-filename: 'templates/service.yaml'
+`,
+		},
+		{
+			name: "mid-content doc separator glued to content by template whitespace trimming",
+			files: map[string]string{
+				"templates/all.yaml": "apiVersion: v1\nkind: ConfigMap\nmetadata:\n  name: test-cm\n---apiVersion: v1\nkind: Service\nmetadata:\n  name: test-svc\n",
+			},
+			expected: `apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: test-cm
+  annotations:
+    postrenderer.helm.sh/postrender-filename: 'templates/all.yaml'
+---
+apiVersion: v1
+kind: Service
+metadata:
+  name: test-svc
+  annotations:
+    postrenderer.helm.sh/postrender-filename: 'templates/all.yaml'
+`,
+		},
 	}
 
 	for _, tt := range tests {