fix: preserve original YAML formatting in resource output

Previously, Resource.AsYAML() used yaml.JSONToYAML which caused two issues:

1. Long lines were automatically wrapped at ~80 characters, breaking
   shell commands and template strings (e.g., Helm-style {{ }})
2. Quote styles were inconsistently modified - sometimes removed,
   sometimes added

This change switches to using kyaml's encoder (RNode.MustString) which
preserves the original YAML formatting, including:
- Long lines remain on a single line
- Quote styles ('single', "double", or unquoted) are preserved

This is a more consistent behavior that respects the user's original
YAML structure.

Related to:
- #947
- #3969

Author: Rindrics

api/krusty/stringquoteblank_test.go

@@ -9,11 +9,8 @@ import (
 	kusttest_test "sigs.k8s.io/kustomize/api/testutils/kusttest"
 )
 
-// This test is for output string style.
-// Currently all quotes will be removed if the string is valid as plain (unquoted) style.
-// If a string cannot be unquoted, it will be put into a pair of single quotes.
-// See https://yaml.org/spec/1.2/spec.html#id2788859 for more details about what kind of string
-// is invalid as plain style.
+// This test verifies that long lines are NOT wrapped in YAML output.
+// See https://github.com/kubernetes-sigs/kustomize/issues/947
 func TestLongLineBreaks(t *testing.T) {
 	th := kusttest_test.MakeHarness(t)
 	th.WriteF("deployment.yaml", `
@@ -59,27 +56,24 @@ spec:
   template:
     spec:
       containers:
-      - env:
+      - name: mariadb
+        image: test
+        env:
         - name: SHORT_STRING
           value: short_string
         - name: SHORT_STRING_WITH_SINGLE_QUOTE
-          value: short_string
+          value: 'short_string'
         - name: SHORT_STRING_WITH_DOUBLE_QUOTE
-          value: short_string
+          value: "short_string"
         - name: SHORT_STRING_BLANK
           value: short string
         - name: LONG_STRING_BLANK
-          value: Lorem ipsum dolor sit amet, consectetur adipiscing elit. Maecenas
-            suscipit ex non molestie varius.
+          value: Lorem ipsum dolor sit amet, consectetur adipiscing elit. Maecenas suscipit ex non molestie varius.
         - name: LONG_STRING_BLANK_WITH_SINGLE_QUOTE
-          value: Lorem ipsum dolor sit amet, consectetur adipiscing elit. Maecenas
-            suscipit ex non molestie varius.
+          value: 'Lorem ipsum dolor sit amet, consectetur adipiscing elit. Maecenas suscipit ex non molestie varius.'
         - name: LONG_STRING_BLANK_WITH_DOUBLE_QUOTE
-          value: Lorem ipsum dolor sit amet, consectetur adipiscing elit. Maecenas
-            suscipit ex non molestie varius.
+          value: "Lorem ipsum dolor sit amet, consectetur adipiscing elit. Maecenas suscipit ex non molestie varius."
         - name: INVALID_PLAIN_STYLE_STRING
           value: ': test'
-        image: test
-        name: mariadb
 `)
 }

api/resource/resource.go

@@ -380,14 +380,13 @@ func (r *Resource) String() string {
 // AsYAML returns the resource in Yaml form.
 // Easier to read than JSON.
 func (r *Resource) AsYAML() ([]byte, error) {
-	json, err := r.MarshalJSON()
-	if err != nil {
-		return nil, err
-	}
-	return yaml.JSONToYAML(json)
+	// Use kyaml's encoder directly to preserve original formatting
+	// and avoid line wrapping issues with sigs.k8s.io/yaml.JSONToYAML.
+	// See https://github.com/kubernetes-sigs/kustomize/issues/947
+	return []byte(r.MustString()), nil
 }
 
-// MustYaml returns YAML or panics.
+// MustYaml returns YAML or panics.	
 func (r *Resource) MustYaml() string {
 	yml, err := r.AsYAML()
 	if err != nil {