Add function to check is YNode zero

kyaml/yaml/rnode.go

@@ -197,7 +197,8 @@ func (rn *RNode) IsNilOrEmpty() bool {
 	return rn.IsNil() ||
 		IsYNodeTaggedNull(rn.YNode()) ||
 		IsYNodeEmptyMap(rn.YNode()) ||
-		IsYNodeEmptySeq(rn.YNode())
+		IsYNodeEmptySeq(rn.YNode()) ||
+		IsYNodeZero(rn.YNode())
 }
 
 // GetMeta returns the ResourceMeta for an RNode

kyaml/yaml/rnode_test.go

@@ -750,6 +750,10 @@ func TestRNodeIsNilOrEmpty(t *testing.T) {
 	if NewListRNode("foo").IsNilOrEmpty() {
 		t.Fatalf("non-empty list should not be empty")
 	}
+
+	if !NewRNode(&Node{}).IsNilOrEmpty() {
+		t.Fatalf("zero YNode should be empty")
+	}
 }
 
 const deploymentJSON = `

kyaml/yaml/types.go

@@ -54,6 +54,18 @@ func IsYNodeString(n *yaml.Node) bool {
 	return n.Kind == yaml.ScalarNode && n.Tag == NodeTagString
 }
 
+// IsYNodeZero is true if all the public fields in the Node are empty.
+// Which means it's not initialized and should be omitted when marshal.
+// The Node itself has a method IsZero but it is not released
+// in yaml.v3. https://pkg.go.dev/gopkg.in/yaml.v3#Node.IsZero
+func IsYNodeZero(n *yaml.Node) bool {
+	// TODO: Change this to use IsZero when it's avaialable.
+	return n != nil && n.Kind == 0 && n.Style == 0 && n.Tag == "" && n.Value == "" &&
+		n.Anchor == "" && n.Alias == nil && n.Content == nil &&
+		n.HeadComment == "" && n.LineComment == "" && n.FootComment == "" &&
+		n.Line == 0 && n.Column == 0
+}
+
 // Parser parses values into configuration.
 type Parser struct {
 	Kind  string `yaml:"kind,omitempty"`

kyaml/yaml/types_test.go

@@ -112,3 +112,15 @@ func TestIsYNodeEmptySeq(t *testing.T) {
 		t.Fatalf("a node with content isn't empty")
 	}
 }
+
+func TestIsYNodeZero(t *testing.T) {
+	if IsYNodeZero(nil) {
+		t.Fatalf("nil node should not be zero")
+	}
+	if !IsYNodeZero(&Node{}) {
+		t.Fatalf("node is zero")
+	}
+	if IsYNodeZero(&Node{Kind: MappingNode}) {
+		t.Fatalf("node is not zero")
+	}
+}