client-fake object tracker: support merge patch

staging/src/k8s.io/client-go/dynamic/fake/simple_test.go

@@ -181,11 +181,11 @@ func TestPatch(t *testing.T) {
 			patchBytes: []byte(`[{"op": "add", "path": "/spec/newvalue", "value": "dummy"}]`),
 			wantErrMsg: "invalid JSON document",
 		}, {
-			name:       "merge patch fails as unsupported",
-			object:     newUnstructured(testAPIVersion, testKind, testNamespace, testName),
-			patchType:  types.MergePatchType,
-			patchBytes: []byte(`{}`),
-			wantErrMsg: "PatchType is not supported",
+			name:                  "merge patch works with simple replacement",
+			object:                newUnstructuredWithSpec(map[string]interface{}{"foo": "bar"}),
+			patchType:             types.MergePatchType,
+			patchBytes:            []byte(`{ "spec": { "foo": "baz" } }`),
+			expectedPatchedObject: newUnstructuredWithSpec(map[string]interface{}{"foo": "baz"}),
 		},
 		// TODO: Add tests for strategic merge using v1.Pod for example to ensure the test cases
 		// demonstrate expected use cases.

staging/src/k8s.io/client-go/testing/fixture.go

@@ -20,7 +20,7 @@ import (
 	"fmt"
 	"sync"
 
-	"github.com/evanphx/json-patch"
+	jsonpatch "github.com/evanphx/json-patch"
 	"k8s.io/apimachinery/pkg/api/errors"
 	"k8s.io/apimachinery/pkg/api/meta"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
@@ -138,7 +138,7 @@ func ObjectReaction(tracker ObjectTracker) ReactionFunc {
 			if err != nil {
 				return true, nil, err
 			}
-			// Only supports strategic merge patch and JSONPatch as coded.
+
 			switch action.GetPatchType() {
 			case types.JSONPatchType:
 				patch, err := jsonpatch.DecodePatch(action.GetPatch())
@@ -152,6 +152,15 @@ func ObjectReaction(tracker ObjectTracker) ReactionFunc {
 				if err = json.Unmarshal(modified, obj); err != nil {
 					return true, nil, err
 				}
+			case types.MergePatchType:
+				modified, err := jsonpatch.MergePatch(old, action.GetPatch())
+				if err != nil {
+					return true, nil, err
+				}
+
+				if err := json.Unmarshal(modified, obj); err != nil {
+					return true, nil, err
+				}
 			case types.StrategicMergePatchType:
 				mergedByte, err := strategicpatch.StrategicMergePatch(old, action.GetPatch(), obj)
 				if err != nil {