Merge pull request #57504 from yue9944882/fix-fake-client-dummy-watch

Automatic merge from submit-queue. If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.

feat(fakeclient): push event on watched channel on add/update/delete

**What this PR does / why we need it**:

This PR enables watch function for kubernetes [fakeclient](1bcf0b0a22/staging/src/k8s.io/client-go/kubernetes/fake/clientset_generated.go (L88)). 

This fake client add watchReactorFunction by wrapping [watch.NewFake](1bcf0b0a22/staging/src/k8s.io/client-go/kubernetes/fake/clientset_generated.go (L98)) which is a `chan Event` but actually nothing pushes objects into this channel. So all watch function called by fake client will never return or never receive any object. 

This PR intercepts ReactionFunc of `Create / Update / DeleteActionImpl` and will push the requested object to channel. 

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):

Fixes #54075

**Special notes for your reviewer**:

**Release note**:

```dev-release-note
enable watch function for fake client
```

pkg/client/clientset_generated/internalclientset/fake/clientset_generated.go

@@ -71,7 +71,15 @@ func NewSimpleClientset(objects ...runtime.Object) *Clientset {
 
 	fakePtr := testing.Fake{}
 	fakePtr.AddReactor("*", "*", testing.ObjectReaction(o))
-	fakePtr.AddWatchReactor("*", testing.DefaultWatchReactor(watch.NewFake(), nil))
+	fakePtr.AddWatchReactor("*", func(action testing.Action) (handled bool, ret watch.Interface, err error) {
+		gvr := action.GetResource()
+		ns := action.GetNamespace()
+		watch, err := o.Watch(gvr, ns)
+		if err != nil {
+			return false, nil, err
+		}
+		return true, watch, nil
+	})
 
 	return &Clientset{fakePtr, &fakediscovery.FakeDiscovery{Fake: &fakePtr}}
 }

staging/src/k8s.io/apiextensions-apiserver/pkg/client/clientset/clientset/fake/clientset_generated.go

@@ -41,7 +41,15 @@ func NewSimpleClientset(objects ...runtime.Object) *Clientset {
 
 	fakePtr := testing.Fake{}
 	fakePtr.AddReactor("*", "*", testing.ObjectReaction(o))
-	fakePtr.AddWatchReactor("*", testing.DefaultWatchReactor(watch.NewFake(), nil))
+	fakePtr.AddWatchReactor("*", func(action testing.Action) (handled bool, ret watch.Interface, err error) {
+		gvr := action.GetResource()
+		ns := action.GetNamespace()
+		watch, err := o.Watch(gvr, ns)
+		if err != nil {
+			return false, nil, err
+		}
+		return true, watch, nil
+	})
 
 	return &Clientset{fakePtr, &fakediscovery.FakeDiscovery{Fake: &fakePtr}}
 }

staging/src/k8s.io/apiextensions-apiserver/pkg/client/clientset/internalclientset/fake/clientset_generated.go

@@ -41,7 +41,15 @@ func NewSimpleClientset(objects ...runtime.Object) *Clientset {
 
 	fakePtr := testing.Fake{}
 	fakePtr.AddReactor("*", "*", testing.ObjectReaction(o))
-	fakePtr.AddWatchReactor("*", testing.DefaultWatchReactor(watch.NewFake(), nil))
+	fakePtr.AddWatchReactor("*", func(action testing.Action) (handled bool, ret watch.Interface, err error) {
+		gvr := action.GetResource()
+		ns := action.GetNamespace()
+		watch, err := o.Watch(gvr, ns)
+		if err != nil {
+			return false, nil, err
+		}
+		return true, watch, nil
+	})
 
 	return &Clientset{fakePtr, &fakediscovery.FakeDiscovery{Fake: &fakePtr}}
 }

staging/src/k8s.io/client-go/kubernetes/fake/clientset_generated.go

@@ -95,7 +95,15 @@ func NewSimpleClientset(objects ...runtime.Object) *Clientset {
 
 	fakePtr := testing.Fake{}
 	fakePtr.AddReactor("*", "*", testing.ObjectReaction(o))
-	fakePtr.AddWatchReactor("*", testing.DefaultWatchReactor(watch.NewFake(), nil))
+	fakePtr.AddWatchReactor("*", func(action testing.Action) (handled bool, ret watch.Interface, err error) {
+		gvr := action.GetResource()
+		ns := action.GetNamespace()
+		watch, err := o.Watch(gvr, ns)
+		if err != nil {
+			return false, nil, err
+		}
+		return true, watch, nil
+	})
 
 	return &Clientset{fakePtr, &fakediscovery.FakeDiscovery{Fake: &fakePtr}}
 }

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

@@ -3,6 +3,7 @@ package(default_visibility = ["//visibility:public"])
 load(
     "@io_bazel_rules_go//go:def.bzl",
     "go_library",
+    "go_test",
 )
 
 go_library(
@@ -28,6 +29,24 @@ go_library(
     ],
 )
 
+go_test(
+    name = "go_default_test",
+    srcs = [
+        "fixture_test.go",
+    ],
+    embed = [":go_default_library"],
+    importpath = "k8s.io/client-go/testing",
+    deps = [
+        "//vendor/github.com/stretchr/testify/assert:go_default_library",
+        "//vendor/k8s.io/apimachinery/pkg/api/meta:go_default_library",
+        "//vendor/k8s.io/apimachinery/pkg/apis/meta/v1/unstructured:go_default_library",
+        "//vendor/k8s.io/apimachinery/pkg/runtime:go_default_library",
+        "//vendor/k8s.io/apimachinery/pkg/runtime/schema:go_default_library",
+        "//vendor/k8s.io/apimachinery/pkg/runtime/serializer:go_default_library",
+        "//vendor/k8s.io/apimachinery/pkg/watch:go_default_library",
+    ],
+)
+
 filegroup(
     name = "package-srcs",
     srcs = glob(["**"]),

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

@@ -29,6 +29,11 @@ import (
 	restclient "k8s.io/client-go/rest"
 )
 
+// FakeWatchBufferSize is the max num of watch event can be buffered in the
+// watch channel. Note that when watch event overflows or exceed this buffer
+// size, manipulations via fake client may be blocked.
+const FakeWatchBufferSize = 128
+
 // ObjectTracker keeps track of objects. It is intended to be used to
 // fake calls to a server by returning objects based on their kind,
 // namespace and name.
@@ -54,6 +59,10 @@ type ObjectTracker interface {
 	// didn't exist in the tracker prior to deletion, Delete returns
 	// no error.
 	Delete(gvr schema.GroupVersionResource, ns, name string) error
+
+	// Watch watches objects from the tracker. Watch returns a channel
+	// which will push added / modified / deleted object.
+	Watch(gvr schema.GroupVersionResource, ns string) (watch.Interface, error)
 }
 
 // ObjectScheme abstracts the implementation of common operations on objects.
@@ -132,6 +141,13 @@ type tracker struct {
 	decoder runtime.Decoder
 	lock    sync.RWMutex
 	objects map[schema.GroupVersionResource][]runtime.Object
+	// The value type of watchers is a map of which the key is either a namespace or
+	// all/non namespace aka "" and its value is list of fake watchers. Each of
+	// fake watcher holds a buffered channel of size "FakeWatchBufferSize" which
+	// is default to 128. Manipulations on resources will broadcast the notification
+	// events into the watchers' channel and note that too many unhandled event may
+	// potentially block the tracker.
+	watchers map[schema.GroupVersionResource]map[string][]*watch.FakeWatcher
 }
 
 var _ ObjectTracker = &tracker{}
@@ -140,9 +156,10 @@ var _ ObjectTracker = &tracker{}
 // of objects for the fake clientset. Mostly useful for unit tests.
 func NewObjectTracker(scheme ObjectScheme, decoder runtime.Decoder) ObjectTracker {
 	return &tracker{
-		scheme:  scheme,
+		scheme:   scheme,
-		decoder: decoder,
+		decoder:  decoder,
-		objects: make(map[schema.GroupVersionResource][]runtime.Object),
+		objects:  make(map[schema.GroupVersionResource][]runtime.Object),
+		watchers: make(map[schema.GroupVersionResource]map[string][]*watch.FakeWatcher),
 	}
 }
 
@@ -185,6 +202,19 @@ func (t *tracker) List(gvr schema.GroupVersionResource, gvk schema.GroupVersionK
 	return list.DeepCopyObject(), nil
 }
 
+func (t *tracker) Watch(gvr schema.GroupVersionResource, ns string) (watch.Interface, error) {
+	t.lock.Lock()
+	defer t.lock.Unlock()
+
+	fakewatcher := watch.NewFakeWithChanSize(FakeWatchBufferSize, true)
+
+	if _, exists := t.watchers[gvr]; !exists {
+		t.watchers[gvr] = make(map[string][]*watch.FakeWatcher)
+	}
+	t.watchers[gvr][ns] = append(t.watchers[gvr][ns], fakewatcher)
+	return fakewatcher, nil
+}
+
 func (t *tracker) Get(gvr schema.GroupVersionResource, ns, name string) (runtime.Object, error) {
 	errNotFound := errors.NewNotFound(gvr.GroupResource(), name)
 
@@ -263,6 +293,19 @@ func (t *tracker) Update(gvr schema.GroupVersionResource, obj runtime.Object, ns
 	return t.add(gvr, obj, ns, true)
 }
 
+func (t *tracker) getWatches(gvr schema.GroupVersionResource, ns string) []*watch.FakeWatcher {
+	watches := []*watch.FakeWatcher{}
+	if t.watchers[gvr] != nil {
+		if w := t.watchers[gvr][ns]; w != nil {
+			watches = append(watches, w...)
+		}
+		if w := t.watchers[gvr][""]; w != nil {
+			watches = append(watches, w...)
+		}
+	}
+	return watches
+}
+
 func (t *tracker) add(gvr schema.GroupVersionResource, obj runtime.Object, ns string, replaceExisting bool) error {
 	t.lock.Lock()
 	defer t.lock.Unlock()
@@ -296,6 +339,9 @@ func (t *tracker) add(gvr schema.GroupVersionResource, obj runtime.Object, ns st
 		}
 		if oldMeta.GetNamespace() == newMeta.GetNamespace() && oldMeta.GetName() == newMeta.GetName() {
 			if replaceExisting {
+				for _, w := range t.getWatches(gvr, ns) {
+					w.Modify(obj)
+				}
 				t.objects[gvr][i] = obj
 				return nil
 			}
@@ -310,6 +356,10 @@ func (t *tracker) add(gvr schema.GroupVersionResource, obj runtime.Object, ns st
 
 	t.objects[gvr] = append(t.objects[gvr], obj)
 
+	for _, w := range t.getWatches(gvr, ns) {
+		w.Add(obj)
+	}
+
 	return nil
 }
 
@@ -342,7 +392,11 @@ func (t *tracker) Delete(gvr schema.GroupVersionResource, ns, name string) error
 			return err
 		}
 		if objMeta.GetNamespace() == ns && objMeta.GetName() == name {
+			obj := t.objects[gvr][i]
 			t.objects[gvr] = append(t.objects[gvr][:i], t.objects[gvr][i+1:]...)
+			for _, w := range t.getWatches(gvr, ns) {
+				w.Delete(obj)
+			}
 			found = true
 			break
 		}

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

@@ -0,0 +1,192 @@
+/*
+Copyright 2015 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.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package testing
+
+import (
+	"fmt"
+	"math/rand"
+	"strconv"
+	"sync"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+
+	"k8s.io/apimachinery/pkg/api/meta"
+	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
+	runtime "k8s.io/apimachinery/pkg/runtime"
+	"k8s.io/apimachinery/pkg/runtime/schema"
+	serializer "k8s.io/apimachinery/pkg/runtime/serializer"
+	"k8s.io/apimachinery/pkg/watch"
+)
+
+func getArbitraryResource(s schema.GroupVersionResource, name, namespace string) *unstructured.Unstructured {
+	return &unstructured.Unstructured{
+		Object: map[string]interface{}{
+			"kind":       s.Resource,
+			"apiVersion": s.Version,
+			"metadata": map[string]interface{}{
+				"name":            name,
+				"namespace":       namespace,
+				"generateName":    "test_generateName",
+				"uid":             "test_uid",
+				"resourceVersion": "test_resourceVersion",
+				"selfLink":        "test_selfLink",
+			},
+			"data": strconv.Itoa(rand.Int()),
+		},
+	}
+}
+
+func TestWatchCallNonNamespace(t *testing.T) {
+	testResource := schema.GroupVersionResource{Group: "", Version: "test_version", Resource: "test_kind"}
+	testObj := getArbitraryResource(testResource, "test_name", "test_namespace")
+	accessor, err := meta.Accessor(testObj)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	ns := accessor.GetNamespace()
+	scheme := runtime.NewScheme()
+	codecs := serializer.NewCodecFactory(scheme)
+	o := NewObjectTracker(scheme, codecs.UniversalDecoder())
+	watch, err := o.Watch(testResource, ns)
+	go func() {
+		err := o.Create(testResource, testObj, ns)
+		if err != nil {
+			t.Errorf("test resource creation failed: %v", err)
+		}
+	}()
+	out := <-watch.ResultChan()
+	assert.Equal(t, testObj, out.Object, "watched object mismatch")
+}
+
+func TestWatchCallAllNamespace(t *testing.T) {
+	testResource := schema.GroupVersionResource{Group: "", Version: "test_version", Resource: "test_kind"}
+	testObj := getArbitraryResource(testResource, "test_name", "test_namespace")
+	accessor, err := meta.Accessor(testObj)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	ns := accessor.GetNamespace()
+	scheme := runtime.NewScheme()
+	codecs := serializer.NewCodecFactory(scheme)
+	o := NewObjectTracker(scheme, codecs.UniversalDecoder())
+	w, err := o.Watch(testResource, "test_namespace")
+	wAll, err := o.Watch(testResource, "")
+	go func() {
+		err := o.Create(testResource, testObj, ns)
+		assert.NoError(t, err, "test resource creation failed")
+	}()
+	out := <-w.ResultChan()
+	outAll := <-wAll.ResultChan()
+	assert.Equal(t, watch.Added, out.Type, "watch event mismatch")
+	assert.Equal(t, watch.Added, outAll.Type, "watch event mismatch")
+	assert.Equal(t, testObj, out.Object, "watched created object mismatch")
+	assert.Equal(t, testObj, outAll.Object, "watched created object mismatch")
+	go func() {
+		err := o.Update(testResource, testObj, ns)
+		assert.NoError(t, err, "test resource updating failed")
+	}()
+	out = <-w.ResultChan()
+	outAll = <-wAll.ResultChan()
+	assert.Equal(t, watch.Modified, out.Type, "watch event mismatch")
+	assert.Equal(t, watch.Modified, outAll.Type, "watch event mismatch")
+	assert.Equal(t, testObj, out.Object, "watched updated object mismatch")
+	assert.Equal(t, testObj, outAll.Object, "watched updated object mismatch")
+	go func() {
+		err := o.Delete(testResource, "test_namespace", "test_name")
+		assert.NoError(t, err, "test resource deletion failed")
+	}()
+	out = <-w.ResultChan()
+	outAll = <-wAll.ResultChan()
+	assert.Equal(t, watch.Deleted, out.Type, "watch event mismatch")
+	assert.Equal(t, watch.Deleted, outAll.Type, "watch event mismatch")
+	assert.Equal(t, testObj, out.Object, "watched deleted object mismatch")
+	assert.Equal(t, testObj, outAll.Object, "watched deleted object mismatch")
+}
+
+func TestWatchCallMultipleInvocation(t *testing.T) {
+	cases := []struct {
+		name string
+		op   watch.EventType
+	}{
+		{
+			"foo",
+			watch.Added,
+		},
+		{
+			"bar",
+			watch.Added,
+		},
+		{
+			"bar",
+			watch.Modified,
+		},
+		{
+			"foo",
+			watch.Deleted,
+		},
+		{
+			"bar",
+			watch.Deleted,
+		},
+	}
+
+	scheme := runtime.NewScheme()
+	codecs := serializer.NewCodecFactory(scheme)
+	testResource := schema.GroupVersionResource{Group: "", Version: "test_version", Resource: "test_kind"}
+
+	o := NewObjectTracker(scheme, codecs.UniversalDecoder())
+	watchNamespaces := []string{
+		"",
+		"",
+		"test_namespace",
+		"test_namespace",
+	}
+	var wg sync.WaitGroup
+	wg.Add(len(watchNamespaces))
+	for idx, watchNamespace := range watchNamespaces {
+		i := idx
+		w, err := o.Watch(testResource, watchNamespace)
+		go func() {
+			assert.NoError(t, err, "watch invocation failed")
+			for _, c := range cases {
+				fmt.Printf("%#v %#v\n", c, i)
+				event := <-w.ResultChan()
+				accessor, err := meta.Accessor(event.Object)
+				if err != nil {
+					t.Fatalf("unexpected error: %v", err)
+				}
+				assert.Equal(t, c.op, event.Type, "watch event mismatched")
+				assert.Equal(t, c.name, accessor.GetName(), "watched object mismatch")
+			}
+			wg.Done()
+		}()
+	}
+	for _, c := range cases {
+		switch c.op {
+		case watch.Added:
+			obj := getArbitraryResource(testResource, c.name, "test_namespace")
+			o.Create(testResource, obj, "test_namespace")
+		case watch.Modified:
+			obj := getArbitraryResource(testResource, c.name, "test_namespace")
+			o.Update(testResource, obj, "test_namespace")
+		case watch.Deleted:
+			o.Delete(testResource, "test_namespace", c.name)
+		}
+	}
+	wg.Wait()
+}

staging/src/k8s.io/code-generator/_examples/apiserver/clientset/internalversion/fake/clientset_generated.go

@@ -43,7 +43,15 @@ func NewSimpleClientset(objects ...runtime.Object) *Clientset {
 
 	fakePtr := testing.Fake{}
 	fakePtr.AddReactor("*", "*", testing.ObjectReaction(o))
-	fakePtr.AddWatchReactor("*", testing.DefaultWatchReactor(watch.NewFake(), nil))
+	fakePtr.AddWatchReactor("*", func(action testing.Action) (handled bool, ret watch.Interface, err error) {
+		gvr := action.GetResource()
+		ns := action.GetNamespace()
+		watch, err := o.Watch(gvr, ns)
+		if err != nil {
+			return false, nil, err
+		}
+		return true, watch, nil
+	})
 
 	return &Clientset{fakePtr, &fakediscovery.FakeDiscovery{Fake: &fakePtr}}
 }

staging/src/k8s.io/code-generator/_examples/apiserver/clientset/versioned/fake/clientset_generated.go

@@ -43,7 +43,15 @@ func NewSimpleClientset(objects ...runtime.Object) *Clientset {
 
 	fakePtr := testing.Fake{}
 	fakePtr.AddReactor("*", "*", testing.ObjectReaction(o))
-	fakePtr.AddWatchReactor("*", testing.DefaultWatchReactor(watch.NewFake(), nil))
+	fakePtr.AddWatchReactor("*", func(action testing.Action) (handled bool, ret watch.Interface, err error) {
+		gvr := action.GetResource()
+		ns := action.GetNamespace()
+		watch, err := o.Watch(gvr, ns)
+		if err != nil {
+			return false, nil, err
+		}
+		return true, watch, nil
+	})
 
 	return &Clientset{fakePtr, &fakediscovery.FakeDiscovery{Fake: &fakePtr}}
 }

staging/src/k8s.io/code-generator/_examples/crd/clientset/versioned/fake/clientset_generated.go

@@ -43,7 +43,15 @@ func NewSimpleClientset(objects ...runtime.Object) *Clientset {
 
 	fakePtr := testing.Fake{}
 	fakePtr.AddReactor("*", "*", testing.ObjectReaction(o))
-	fakePtr.AddWatchReactor("*", testing.DefaultWatchReactor(watch.NewFake(), nil))
+	fakePtr.AddWatchReactor("*", func(action testing.Action) (handled bool, ret watch.Interface, err error) {
+		gvr := action.GetResource()
+		ns := action.GetNamespace()
+		watch, err := o.Watch(gvr, ns)
+		if err != nil {
+			return false, nil, err
+		}
+		return true, watch, nil
+	})
 
 	return &Clientset{fakePtr, &fakediscovery.FakeDiscovery{Fake: &fakePtr}}
 }

staging/src/k8s.io/code-generator/cmd/client-gen/generators/fake/generator_fake_for_clientset.go

@@ -127,7 +127,15 @@ func NewSimpleClientset(objects ...runtime.Object) *Clientset {
 
 	fakePtr := testing.Fake{}
 	fakePtr.AddReactor("*", "*", testing.ObjectReaction(o))
-	fakePtr.AddWatchReactor("*", testing.DefaultWatchReactor(watch.NewFake(), nil))
+	fakePtr.AddWatchReactor("*", func(action testing.Action) (handled bool, ret watch.Interface, err error) {
+		gvr := action.GetResource()
+		ns := action.GetNamespace()
+		watch, err := o.Watch(gvr, ns)
+		if err != nil {
+			return false, nil, err
+		}
+		return true, watch, nil
+	})
 
 	return &Clientset{fakePtr, &fakediscovery.FakeDiscovery{Fake: &fakePtr}}
 }

staging/src/k8s.io/kube-aggregator/pkg/client/clientset_generated/clientset/fake/clientset_generated.go

@@ -41,7 +41,15 @@ func NewSimpleClientset(objects ...runtime.Object) *Clientset {
 
 	fakePtr := testing.Fake{}
 	fakePtr.AddReactor("*", "*", testing.ObjectReaction(o))
-	fakePtr.AddWatchReactor("*", testing.DefaultWatchReactor(watch.NewFake(), nil))
+	fakePtr.AddWatchReactor("*", func(action testing.Action) (handled bool, ret watch.Interface, err error) {
+		gvr := action.GetResource()
+		ns := action.GetNamespace()
+		watch, err := o.Watch(gvr, ns)
+		if err != nil {
+			return false, nil, err
+		}
+		return true, watch, nil
+	})
 
 	return &Clientset{fakePtr, &fakediscovery.FakeDiscovery{Fake: &fakePtr}}
 }

staging/src/k8s.io/kube-aggregator/pkg/client/clientset_generated/internalclientset/fake/clientset_generated.go

@@ -41,7 +41,15 @@ func NewSimpleClientset(objects ...runtime.Object) *Clientset {
 
 	fakePtr := testing.Fake{}
 	fakePtr.AddReactor("*", "*", testing.ObjectReaction(o))
-	fakePtr.AddWatchReactor("*", testing.DefaultWatchReactor(watch.NewFake(), nil))
+	fakePtr.AddWatchReactor("*", func(action testing.Action) (handled bool, ret watch.Interface, err error) {
+		gvr := action.GetResource()
+		ns := action.GetNamespace()
+		watch, err := o.Watch(gvr, ns)
+		if err != nil {
+			return false, nil, err
+		}
+		return true, watch, nil
+	})
 
 	return &Clientset{fakePtr, &fakediscovery.FakeDiscovery{Fake: &fakePtr}}
 }

staging/src/k8s.io/metrics/pkg/client/clientset_generated/clientset/fake/clientset_generated.go

@@ -43,7 +43,15 @@ func NewSimpleClientset(objects ...runtime.Object) *Clientset {
 
 	fakePtr := testing.Fake{}
 	fakePtr.AddReactor("*", "*", testing.ObjectReaction(o))
-	fakePtr.AddWatchReactor("*", testing.DefaultWatchReactor(watch.NewFake(), nil))
+	fakePtr.AddWatchReactor("*", func(action testing.Action) (handled bool, ret watch.Interface, err error) {
+		gvr := action.GetResource()
+		ns := action.GetNamespace()
+		watch, err := o.Watch(gvr, ns)
+		if err != nil {
+			return false, nil, err
+		}
+		return true, watch, nil
+	})
 
 	return &Clientset{fakePtr, &fakediscovery.FakeDiscovery{Fake: &fakePtr}}
 }

staging/src/k8s.io/sample-apiserver/pkg/client/clientset/internalversion/fake/clientset_generated.go

@@ -41,7 +41,15 @@ func NewSimpleClientset(objects ...runtime.Object) *Clientset {
 
 	fakePtr := testing.Fake{}
 	fakePtr.AddReactor("*", "*", testing.ObjectReaction(o))
-	fakePtr.AddWatchReactor("*", testing.DefaultWatchReactor(watch.NewFake(), nil))
+	fakePtr.AddWatchReactor("*", func(action testing.Action) (handled bool, ret watch.Interface, err error) {
+		gvr := action.GetResource()
+		ns := action.GetNamespace()
+		watch, err := o.Watch(gvr, ns)
+		if err != nil {
+			return false, nil, err
+		}
+		return true, watch, nil
+	})
 
 	return &Clientset{fakePtr, &fakediscovery.FakeDiscovery{Fake: &fakePtr}}
 }

staging/src/k8s.io/sample-apiserver/pkg/client/clientset/versioned/fake/clientset_generated.go

@@ -41,7 +41,15 @@ func NewSimpleClientset(objects ...runtime.Object) *Clientset {
 
 	fakePtr := testing.Fake{}
 	fakePtr.AddReactor("*", "*", testing.ObjectReaction(o))
-	fakePtr.AddWatchReactor("*", testing.DefaultWatchReactor(watch.NewFake(), nil))
+	fakePtr.AddWatchReactor("*", func(action testing.Action) (handled bool, ret watch.Interface, err error) {
+		gvr := action.GetResource()
+		ns := action.GetNamespace()
+		watch, err := o.Watch(gvr, ns)
+		if err != nil {
+			return false, nil, err
+		}
+		return true, watch, nil
+	})
 
 	return &Clientset{fakePtr, &fakediscovery.FakeDiscovery{Fake: &fakePtr}}
 }

staging/src/k8s.io/sample-controller/pkg/client/clientset/versioned/fake/clientset_generated.go

@@ -41,7 +41,15 @@ func NewSimpleClientset(objects ...runtime.Object) *Clientset {
 
 	fakePtr := testing.Fake{}
 	fakePtr.AddReactor("*", "*", testing.ObjectReaction(o))
-	fakePtr.AddWatchReactor("*", testing.DefaultWatchReactor(watch.NewFake(), nil))
+	fakePtr.AddWatchReactor("*", func(action testing.Action) (handled bool, ret watch.Interface, err error) {
+		gvr := action.GetResource()
+		ns := action.GetNamespace()
+		watch, err := o.Watch(gvr, ns)
+		if err != nil {
+			return false, nil, err
+		}
+		return true, watch, nil
+	})
 
 	return &Clientset{fakePtr, &fakediscovery.FakeDiscovery{Fake: &fakePtr}}
 }