Support typed nils; test empty Unstructured is not mutated

pkg/printers/internalversion/describe_test.go

@@ -2133,14 +2133,14 @@ URL:	http://localhost
 				"name":              "MyName",
 				"namespace":         "MyNamespace",
 				"creationTimestamp": "2017-04-01T00:00:00Z",
-				"resourceVersion":   int64(123),
+				"resourceVersion":   123,
 				"uid":               "00000000-0000-0000-0000-000000000001",
 				"dummy3":            "present",
 			},
 			"items": []interface{}{
 				map[string]interface{}{
 					"itemBool": true,
-					"itemInt":  int64(42),
+					"itemInt":  42,
 				},
 			},
 			"url":    "http://localhost",

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

@@ -1,5 +1,5 @@
 /*
-Copyright 2017 The Kubernetes Authors.
+Copyright 2018 The Kubernetes Authors.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -24,7 +24,9 @@ import (
 
 func TestNilUnstructuredContent(t *testing.T) {
 	var u Unstructured
+	uCopy := u.DeepCopy()
 	content := u.UnstructuredContent()
 	expContent := make(map[string]interface{})
 	assert.EqualValues(t, expContent, content)
+	assert.Equal(t, uCopy, &u)
 }

staging/src/k8s.io/apimachinery/pkg/runtime/converter.go

@@ -446,20 +446,31 @@ func DeepCopyJSON(x map[string]interface{}) map[string]interface{} {
 // DeepCopyJSONValue deep copies the passed value, assuming it is a valid JSON representation i.e. only contains
 // types produced by json.Unmarshal().
 func DeepCopyJSONValue(x interface{}) interface{} {
+	if x == nil {
+		return nil
+	}
 	switch x := x.(type) {
 	case map[string]interface{}:
+		if x == nil {
+			// Typed nil - an interface{} that contains a type map[string]interface{} with a value of nil
+			return x
+		}
 		clone := make(map[string]interface{}, len(x))
 		for k, v := range x {
 			clone[k] = DeepCopyJSONValue(v)
 		}
 		return clone
 	case []interface{}:
+		if x == nil {
+			// Typed nil - an interface{} that contains a type []interface{} with a value of nil
+			return x
+		}
 		clone := make([]interface{}, len(x))
 		for i, v := range x {
 			clone[i] = DeepCopyJSONValue(v)
 		}
 		return clone
-	case string, int64, bool, float64, nil, encodingjson.Number:
+	case string, int64, bool, float64, encodingjson.Number:
 		return x
 	default:
 		panic(fmt.Errorf("cannot deep copy %T", x))