export unstructured helper function nestedFieldNoCopy and add unit tests

Signed-off-by: Steve Kriss <steve@heptio.com>

staging/src/k8s.io/apimachinery/pkg/apis/meta/v1/unstructured/helpers.go

@@ -34,14 +34,17 @@ import (
 // Returns false if the value is missing.
 // No error is returned for a nil field.
 func NestedFieldCopy(obj map[string]interface{}, fields ...string) (interface{}, bool, error) {
-	val, found, err := nestedFieldNoCopy(obj, fields...)
+	val, found, err := NestedFieldNoCopy(obj, fields...)
 	if !found || err != nil {
 		return nil, found, err
 	}
 	return runtime.DeepCopyJSONValue(val), true, nil
 }
 
-func nestedFieldNoCopy(obj map[string]interface{}, fields ...string) (interface{}, bool, error) {
+// NestedFieldNoCopy returns a reference to a nested field.
+// Returns false if value is not found and an error if unable
+// to traverse obj.
+func NestedFieldNoCopy(obj map[string]interface{}, fields ...string) (interface{}, bool, error) {
 	var val interface{} = obj
 
 	for i, field := range fields {
@@ -60,7 +63,7 @@ func nestedFieldNoCopy(obj map[string]interface{}, fields ...string) (interface{
 // NestedString returns the string value of a nested field.
 // Returns false if value is not found and an error if not a string.
 func NestedString(obj map[string]interface{}, fields ...string) (string, bool, error) {
-	val, found, err := nestedFieldNoCopy(obj, fields...)
+	val, found, err := NestedFieldNoCopy(obj, fields...)
 	if !found || err != nil {
 		return "", found, err
 	}
@@ -74,7 +77,7 @@ func NestedString(obj map[string]interface{}, fields ...string) (string, bool, e
 // NestedBool returns the bool value of a nested field.
 // Returns false if value is not found and an error if not a bool.
 func NestedBool(obj map[string]interface{}, fields ...string) (bool, bool, error) {
-	val, found, err := nestedFieldNoCopy(obj, fields...)
+	val, found, err := NestedFieldNoCopy(obj, fields...)
 	if !found || err != nil {
 		return false, found, err
 	}
@@ -88,7 +91,7 @@ func NestedBool(obj map[string]interface{}, fields ...string) (bool, bool, error
 // NestedFloat64 returns the float64 value of a nested field.
 // Returns false if value is not found and an error if not a float64.
 func NestedFloat64(obj map[string]interface{}, fields ...string) (float64, bool, error) {
-	val, found, err := nestedFieldNoCopy(obj, fields...)
+	val, found, err := NestedFieldNoCopy(obj, fields...)
 	if !found || err != nil {
 		return 0, found, err
 	}
@@ -102,7 +105,7 @@ func NestedFloat64(obj map[string]interface{}, fields ...string) (float64, bool,
 // NestedInt64 returns the int64 value of a nested field.
 // Returns false if value is not found and an error if not an int64.
 func NestedInt64(obj map[string]interface{}, fields ...string) (int64, bool, error) {
-	val, found, err := nestedFieldNoCopy(obj, fields...)
+	val, found, err := NestedFieldNoCopy(obj, fields...)
 	if !found || err != nil {
 		return 0, found, err
 	}
@@ -116,7 +119,7 @@ func NestedInt64(obj map[string]interface{}, fields ...string) (int64, bool, err
 // NestedStringSlice returns a copy of []string value of a nested field.
 // Returns false if value is not found and an error if not a []interface{} or contains non-string items in the slice.
 func NestedStringSlice(obj map[string]interface{}, fields ...string) ([]string, bool, error) {
-	val, found, err := nestedFieldNoCopy(obj, fields...)
+	val, found, err := NestedFieldNoCopy(obj, fields...)
 	if !found || err != nil {
 		return nil, found, err
 	}
@@ -138,7 +141,7 @@ func NestedStringSlice(obj map[string]interface{}, fields ...string) ([]string,
 // NestedSlice returns a deep copy of []interface{} value of a nested field.
 // Returns false if value is not found and an error if not a []interface{}.
 func NestedSlice(obj map[string]interface{}, fields ...string) ([]interface{}, bool, error) {
-	val, found, err := nestedFieldNoCopy(obj, fields...)
+	val, found, err := NestedFieldNoCopy(obj, fields...)
 	if !found || err != nil {
 		return nil, found, err
 	}
@@ -180,7 +183,7 @@ func NestedMap(obj map[string]interface{}, fields ...string) (map[string]interfa
 // nestedMapNoCopy returns a map[string]interface{} value of a nested field.
 // Returns false if value is not found and an error if not a map[string]interface{}.
 func nestedMapNoCopy(obj map[string]interface{}, fields ...string) (map[string]interface{}, bool, error) {
-	val, found, err := nestedFieldNoCopy(obj, fields...)
+	val, found, err := NestedFieldNoCopy(obj, fields...)
 	if !found || err != nil {
 		return nil, found, err
 	}

staging/src/k8s.io/apimachinery/pkg/apis/meta/v1/unstructured/helpers_test.go

@@ -58,3 +58,79 @@ func TestRemoveNestedField(t *testing.T) {
 	RemoveNestedField(obj, "x") // Remove of a non-existent field
 	assert.Empty(t, obj)
 }
+
+func TestNestedFieldNoCopy(t *testing.T) {
+	target := map[string]interface{}{"foo": "bar"}
+
+	obj := map[string]interface{}{
+		"a": map[string]interface{}{
+			"b": target,
+			"c": nil,
+			"d": []interface{}{"foo"},
+		},
+	}
+
+	// case 1: field exists and is non-nil
+	res, exists, err := NestedFieldNoCopy(obj, "a", "b")
+	assert.True(t, exists)
+	assert.Nil(t, err)
+	assert.Equal(t, target, res)
+	target["foo"] = "baz"
+	assert.Equal(t, target["foo"], res.(map[string]interface{})["foo"], "result should be a reference to the expected item")
+
+	// case 2: field exists and is nil
+	res, exists, err = NestedFieldNoCopy(obj, "a", "c")
+	assert.True(t, exists)
+	assert.Nil(t, err)
+	assert.Nil(t, res)
+
+	// case 3: error traversing obj
+	res, exists, err = NestedFieldNoCopy(obj, "a", "d", "foo")
+	assert.False(t, exists)
+	assert.NotNil(t, err)
+	assert.Nil(t, res)
+
+	// case 4: field does not exist
+	res, exists, err = NestedFieldNoCopy(obj, "a", "e")
+	assert.False(t, exists)
+	assert.Nil(t, err)
+	assert.Nil(t, res)
+}
+
+func TestNestedFieldCopy(t *testing.T) {
+	target := map[string]interface{}{"foo": "bar"}
+
+	obj := map[string]interface{}{
+		"a": map[string]interface{}{
+			"b": target,
+			"c": nil,
+			"d": []interface{}{"foo"},
+		},
+	}
+
+	// case 1: field exists and is non-nil
+	res, exists, err := NestedFieldCopy(obj, "a", "b")
+	assert.True(t, exists)
+	assert.Nil(t, err)
+	assert.Equal(t, target, res)
+	target["foo"] = "baz"
+	assert.NotEqual(t, target["foo"], res.(map[string]interface{})["foo"], "result should be a copy of the expected item")
+
+	// case 2: field exists and is nil
+	res, exists, err = NestedFieldCopy(obj, "a", "c")
+	assert.True(t, exists)
+	assert.Nil(t, err)
+	assert.Nil(t, res)
+
+	// case 3: error traversing obj
+	res, exists, err = NestedFieldCopy(obj, "a", "d", "foo")
+	assert.False(t, exists)
+	assert.NotNil(t, err)
+	assert.Nil(t, res)
+
+	// case 4: field does not exist
+	res, exists, err = NestedFieldCopy(obj, "a", "e")
+	assert.False(t, exists)
+	assert.Nil(t, err)
+	assert.Nil(t, res)
+}

staging/src/k8s.io/apimachinery/pkg/apis/meta/v1/unstructured/unstructured.go

@@ -138,7 +138,7 @@ func (u *Unstructured) setNestedMap(value map[string]string, fields ...string) {
 }
 
 func (u *Unstructured) GetOwnerReferences() []metav1.OwnerReference {
-	field, found, err := nestedFieldNoCopy(u.Object, "metadata", "ownerReferences")
+	field, found, err := NestedFieldNoCopy(u.Object, "metadata", "ownerReferences")
 	if !found || err != nil {
 		return nil
 	}