fix: render empty scalar nodes

datamodel/high/node_builder.go

@@ -500,6 +500,13 @@ func (n *NodeBuilder) AddYAMLNode(parent *yaml.Node, entry *nodes.NodeEntry) *ya
 					valueNode.Line = line
 				}
 			}
+			if b, bok := value.(*yaml.Node); bok {
+				if b.Kind == yaml.ScalarNode && b.Tag == "!!null" {
+					encodeSkip = true
+					valueNode = utils.CreateEmptyScalarNode()
+					valueNode.Line = line
+				}
+			}
 			if !encodeSkip {
 				var rawNode yaml.Node
 				err := rawNode.Encode(value)

datamodel/high/v3/document_test.go

@@ -635,6 +635,25 @@ func TestDocument_MarshalIndention(t *testing.T) {
 	}
 }
 
+func TestDocument_Nullable_Example(t *testing.T) {
+	data, _ := os.ReadFile("../../../test_specs/nullable-examples.openapi.yaml")
+	info, _ := datamodel.ExtractSpecInfo(data)
+
+	lowDoc, _ = lowv3.CreateDocumentFromConfig(info, datamodel.NewDocumentConfiguration())
+
+	highDoc := NewDocument(lowDoc)
+	rendered := highDoc.RenderWithIndention(2)
+
+	if runtime.GOOS != "windows" {
+		assert.Equal(t, string(data), strings.TrimSpace(string(rendered)))
+	}
+
+	rendered = highDoc.RenderWithIndention(4)
+	if runtime.GOOS != "windows" {
+		assert.NotEqual(t, string(data), strings.TrimSpace(string(rendered)))
+	}
+}
+
 func TestDocument_MarshalIndention_Error(t *testing.T) {
 	data, _ := os.ReadFile("../../../test_specs/single-definition.yaml")
 	info, _ := datamodel.ExtractSpecInfo(data)

test_specs/nullable-examples.openapi.yaml

@@ -0,0 +1,14 @@
+openapi: 3.1.0
+components:
+  schemas:
+    Thing:
+      type: object
+      description: A nullable example.
+      properties:
+        target:
+          nullable: true
+          type: string
+          enum:
+            - staging
+            - production
+          example:

utils/nodes.go

@@ -67,6 +67,15 @@ func CreateIntNode(str string) *yaml.Node {
 	return n
 }
 
+func CreateEmptyScalarNode() *yaml.Node {
+	n := &yaml.Node{
+		Kind:  yaml.ScalarNode,
+		Tag:   "!!null",
+		Value: "",
+	}
+	return n
+}
+
 func CreateFloatNode(str string) *yaml.Node {
 	n := &yaml.Node{
 		Kind:  yaml.ScalarNode,