client-go/testing: properly handle Patch actions for missing Objects

Currently the fake client will return a default empty Object when a
Patch action is submitted on a missing Object. The correct behavior is to
instead propagate the NotFound error.

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

@@ -42,6 +42,7 @@ go_test(
         "//staging/src/k8s.io/apimachinery/pkg/runtime:go_default_library",
         "//staging/src/k8s.io/apimachinery/pkg/runtime/schema:go_default_library",
         "//staging/src/k8s.io/apimachinery/pkg/runtime/serializer:go_default_library",
+        "//staging/src/k8s.io/apimachinery/pkg/types:go_default_library",
         "//staging/src/k8s.io/apimachinery/pkg/watch:go_default_library",
         "//vendor/github.com/stretchr/testify/assert:go_default_library",
     ],

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

@@ -131,8 +131,7 @@ func ObjectReaction(tracker ObjectTracker) ReactionFunc {
 		case PatchActionImpl:
 			obj, err := tracker.Get(gvr, ns, action.GetName())
 			if err != nil {
-				// object is not registered
-				return false, nil, err
+				return true, nil, err
 			}
 
 			old, err := json.Marshal(obj)

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

@@ -30,6 +30,7 @@ import (
 	runtime "k8s.io/apimachinery/pkg/runtime"
 	"k8s.io/apimachinery/pkg/runtime/schema"
 	serializer "k8s.io/apimachinery/pkg/runtime/serializer"
+	"k8s.io/apimachinery/pkg/types"
 	"k8s.io/apimachinery/pkg/watch"
 )
 
@@ -258,3 +259,17 @@ func TestWatchAddAfterStop(t *testing.T) {
 		t.Errorf("test resource creation failed: %v", err)
 	}
 }
+
+func TestPatchWithMissingObject(t *testing.T) {
+	nodesResource := schema.GroupVersionResource{Group: "", Version: "v1", Resource: "nodes"}
+
+	scheme := runtime.NewScheme()
+	codecs := serializer.NewCodecFactory(scheme)
+	o := NewObjectTracker(scheme, codecs.UniversalDecoder())
+	reaction := ObjectReaction(o)
+	action := NewRootPatchSubresourceAction(nodesResource, "node-1", types.StrategicMergePatchType, []byte(`{}`))
+	handled, node, err := reaction(action)
+	assert.True(t, handled)
+	assert.Nil(t, node)
+	assert.EqualError(t, err, `nodes "node-1" not found`)
+}