Add RNode fromMap method.

kyaml/yaml/rnode.go

@@ -318,8 +318,7 @@ func (rn *RNode) PipeE(functions ...Filter) error {
 	return errors.Wrap(err)
 }
 
-// Document returns the Node RNode for the value.  Does not unwrap the node if it is a
-// DocumentNodes
+// Document returns the Node for the value.
 func (rn *RNode) Document() *yaml.Node {
 	return rn.value
 }
@@ -565,6 +564,7 @@ func (rn *RNode) GetAssociativeKey() string {
 	return ""
 }
 
+// MarshalJSON creates a byte slice from the RNode.
 func (rn *RNode) MarshalJSON() ([]byte, error) {
 	s, err := rn.String()
 	if err != nil {
@@ -586,18 +586,13 @@ func (rn *RNode) MarshalJSON() ([]byte, error) {
 	return json.Marshal(m)
 }
 
+// UnmarshalJSON overwrites this RNode with data from []byte.
 func (rn *RNode) UnmarshalJSON(b []byte) error {
 	m := map[string]interface{}{}
 	if err := json.Unmarshal(b, &m); err != nil {
 		return err
 	}
-
-	c, err := Marshal(m)
-	if err != nil {
-		return err
-	}
-
-	r, err := Parse(string(c))
+	r, err := FromMap(m)
 	if err != nil {
 		return err
 	}
@@ -605,6 +600,14 @@ func (rn *RNode) UnmarshalJSON(b []byte) error {
 	return nil
 }
 
+func FromMap(m map[string]interface{}) (*RNode, error) {
+	c, err := Marshal(m)
+	if err != nil {
+		return nil, err
+	}
+	return Parse(string(c))
+}
+
 // ConvertJSONToYamlNode parses input json string and returns equivalent yaml node
 func ConvertJSONToYamlNode(jsonStr string) (*RNode, error) {
 	var body map[string]interface{}

kyaml/yaml/rnode_test.go

@@ -11,6 +11,137 @@ import (
 	"github.com/stretchr/testify/assert"
 )
 
+func TestRNodeFromMap(t *testing.T) {
+	testConfigMap := map[string]interface{}{
+		"apiVersion": "v1",
+		"kind":       "ConfigMap",
+		"metadata": map[string]interface{}{
+			"name": "winnie",
+		},
+	}
+	type thingExpected struct {
+		out string
+		err error
+	}
+
+	testCases := map[string]struct {
+		theMap   map[string]interface{}
+		expected thingExpected
+	}{
+		"actuallyNil": {
+			theMap: nil,
+			expected: thingExpected{
+				out: `{}`,
+				err: nil,
+			},
+		},
+		"empty": {
+			theMap: map[string]interface{}{},
+			expected: thingExpected{
+				out: `{}`,
+				err: nil,
+			},
+		},
+		"mostlyEmpty": {
+			theMap: map[string]interface{}{
+				"hey": "there",
+			},
+			expected: thingExpected{
+				out: `hey: there`,
+				err: nil,
+			},
+		},
+		"configmap": {
+			theMap: testConfigMap,
+			expected: thingExpected{
+				out: `
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: winnie
+`,
+				err: nil,
+			},
+		},
+		"list": {
+			theMap: map[string]interface{}{
+				"apiVersion": "v1",
+				"kind":       "List",
+				"items": []interface{}{
+					testConfigMap,
+					testConfigMap,
+				},
+			},
+			expected: thingExpected{
+				out: `
+apiVersion: v1
+items:
+- apiVersion: v1
+  kind: ConfigMap
+  metadata:
+    name: winnie
+- apiVersion: v1
+  kind: ConfigMap
+  metadata:
+    name: winnie
+kind: List
+`,
+				err: nil,
+			},
+		},
+		"configmaplist": {
+			theMap: map[string]interface{}{
+				"apiVersion": "v1",
+				"kind":       "ConfigMapList",
+				"items": []interface{}{
+					testConfigMap,
+					testConfigMap,
+				},
+			},
+			expected: thingExpected{
+				out: `
+apiVersion: v1
+items:
+- apiVersion: v1
+  kind: ConfigMap
+  metadata:
+    name: winnie
+- apiVersion: v1
+  kind: ConfigMap
+  metadata:
+    name: winnie
+kind: ConfigMapList
+`,
+				err: nil,
+			},
+		},
+	}
+
+	for n := range testCases {
+		tc := testCases[n]
+		t.Run(n, func(t *testing.T) {
+			rn, err := FromMap(tc.theMap)
+			if tc.expected.err == nil {
+				if !assert.NoError(t, err) {
+					t.FailNow()
+				}
+				if !assert.Equal(t,
+					strings.TrimSpace(tc.expected.out),
+					strings.TrimSpace(rn.MustString())) {
+					t.FailNow()
+				}
+			} else {
+				if !assert.Error(t, err) {
+					t.FailNow()
+				}
+				if !assert.Equal(t, tc.expected.err, err) {
+					t.FailNow()
+				}
+			}
+		})
+	}
+}
+
 // Test that non-UTF8 characters in comments don't cause failures
 func TestRNode_GetMeta_UTF16(t *testing.T) {
 	sr, err := Parse(`apiVersion: rbac.istio.io/v1alpha1