✨ Improve the fake client builder with WithObjectTracker option (#1863)

* Improve the fake client builder with WithObjectTracker option

* Update unit test to cover WithObjectTracker

* Update unit test to cover WithObjectTracker

* Update unit test with goimports

pkg/client/fake/client.go

@@ -92,6 +92,7 @@ type ClientBuilder struct {
 	initObject         []client.Object
 	initLists          []client.ObjectList
 	initRuntimeObjects []runtime.Object
+	objectTracker      testing.ObjectTracker
 }
 
 // WithScheme sets this builder's internal scheme.
@@ -128,6 +129,12 @@ func (f *ClientBuilder) WithRuntimeObjects(initRuntimeObjs ...runtime.Object) *C
 	return f
 }
 
+// WithObjectTracker can be optionally used to initialize this fake client with testing.ObjectTracker.
+func (f *ClientBuilder) WithObjectTracker(ot testing.ObjectTracker) *ClientBuilder {
+	f.objectTracker = ot
+	return f
+}
+
 // Build builds and returns a new fake client.
 func (f *ClientBuilder) Build() client.WithWatch {
 	if f.scheme == nil {
@@ -137,7 +144,14 @@ func (f *ClientBuilder) Build() client.WithWatch {
 		f.restMapper = meta.NewDefaultRESTMapper([]schema.GroupVersion{})
 	}
 
-	tracker := versionedTracker{ObjectTracker: testing.NewObjectTracker(f.scheme, scheme.Codecs.UniversalDecoder()), scheme: f.scheme}
+	var tracker versionedTracker
+
+	if f.objectTracker == nil {
+		tracker = versionedTracker{ObjectTracker: testing.NewObjectTracker(f.scheme, scheme.Codecs.UniversalDecoder()), scheme: f.scheme}
+	} else {
+		tracker = versionedTracker{ObjectTracker: f.objectTracker, scheme: f.scheme}
+	}
+
 	for _, obj := range f.initObject {
 		if err := tracker.Add(obj); err != nil {
 			panic(fmt.Errorf("failed to add object %v to fake client: %w", obj, err))

pkg/client/fake/client_test.go

@@ -22,6 +22,8 @@ import (
 	"fmt"
 	"time"
 
+	"k8s.io/client-go/kubernetes/fake"
+
 	. "github.com/onsi/ginkgo"
 	. "github.com/onsi/gomega"
 	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
@@ -1002,4 +1004,53 @@ var _ = Describe("Fake client", func() {
 		}
 		Expect(retrieved).To(Equal(reference))
 	})
+
+	It("should be able to build with given tracker and get resource", func() {
+		clientSet := fake.NewSimpleClientset(dep)
+		cl := NewClientBuilder().WithRuntimeObjects(dep2).WithObjectTracker(clientSet.Tracker()).Build()
+
+		By("Getting a deployment")
+		namespacedName := types.NamespacedName{
+			Name:      "test-deployment",
+			Namespace: "ns1",
+		}
+		obj := &appsv1.Deployment{}
+		err := cl.Get(context.Background(), namespacedName, obj)
+		Expect(err).To(BeNil())
+		Expect(obj).To(Equal(dep))
+
+		By("Getting a deployment from clientSet")
+		csDep2, err := clientSet.AppsV1().Deployments("ns1").Get(context.Background(), "test-deployment-2", metav1.GetOptions{})
+		Expect(err).To(BeNil())
+		Expect(csDep2).To(Equal(dep2))
+
+		By("Getting a new deployment")
+		namespacedName3 := types.NamespacedName{
+			Name:      "test-deployment-3",
+			Namespace: "ns1",
+		}
+
+		dep3 := &appsv1.Deployment{
+			TypeMeta: metav1.TypeMeta{
+				APIVersion: "apps/v1",
+				Kind:       "Deployment",
+			},
+			ObjectMeta: metav1.ObjectMeta{
+				Name:      "test-deployment-3",
+				Namespace: "ns1",
+				Labels: map[string]string{
+					"test-label": "label-value",
+				},
+				ResourceVersion: trackerAddResourceVersion,
+			},
+		}
+
+		_, err = clientSet.AppsV1().Deployments("ns1").Create(context.Background(), dep3, metav1.CreateOptions{})
+		Expect(err).To(BeNil())
+
+		obj = &appsv1.Deployment{}
+		err = cl.Get(context.Background(), namespacedName3, obj)
+		Expect(err).To(BeNil())
+		Expect(obj).To(Equal(dep3))
+	})
 })