Allow to wire a mutation handler

pkg/builder/webhook.go

@@ -37,6 +37,7 @@ import (
 // WebhookBuilder builds a Webhook.
 type WebhookBuilder struct {
 	apiType         runtime.Object
+	mutatorFactory  admission.HandlerFactory
 	customDefaulter admission.CustomDefaulter
 	customValidator admission.CustomValidator
 	gvk             schema.GroupVersionKind
@@ -65,6 +66,12 @@ func (blder *WebhookBuilder) For(apiType runtime.Object) *WebhookBuilder {
 	return blder
 }
 
+// WithMutationHandler takes an admission.ObjectHandler interface, a MutatingWebhook will be wired for this type.
+func (blder *WebhookBuilder) WithMutatorFactory(factory admission.HandlerFactory) *WebhookBuilder {
+	blder.mutatorFactory = factory
+	return blder
+}
+
 // WithDefaulter takes an admission.CustomDefaulter interface, a MutatingWebhook will be wired for this type.
 func (blder *WebhookBuilder) WithDefaulter(defaulter admission.CustomDefaulter) *WebhookBuilder {
 	blder.customDefaulter = defaulter
@@ -169,14 +176,19 @@ func (blder *WebhookBuilder) registerDefaultingWebhook() {
 }
 
 func (blder *WebhookBuilder) getDefaultingWebhook() *admission.Webhook {
-	if defaulter := blder.customDefaulter; defaulter != nil {
-		w := admission.WithCustomDefaulter(blder.mgr.GetScheme(), blder.apiType, defaulter)
-		if blder.recoverPanic != nil {
-			w = w.WithRecoverPanic(*blder.recoverPanic)
-		}
-		return w
+	var w *admission.Webhook
+	if factory := blder.mutatorFactory; factory != nil {
+		w = admission.WithHandlerFactory(blder.mgr.GetScheme(), blder.apiType, factory)
+	} else if defaulter := blder.customDefaulter; defaulter != nil {
+		w = admission.WithCustomDefaulter(blder.mgr.GetScheme(), blder.apiType, defaulter)
 	}
-	return nil
+	if w == nil {
+		return nil
+	}
+	if blder.recoverPanic != nil {
+		w = w.WithRecoverPanic(*blder.recoverPanic)
+	}
+	return w
 }
 
 // registerValidatingWebhook registers a validating webhook if necessary.

pkg/builder/webhook_test.go

@@ -288,6 +288,82 @@ func runTests(admissionReviewVersion string) {
 		ExpectWithOffset(1, w.Code).To(Equal(http.StatusNotFound))
 	})
 
+	It("should scaffold a mutating webhook with a mutator", func() {
+		By("creating a controller manager")
+		m, err := manager.New(cfg, manager.Options{})
+		ExpectWithOffset(1, err).NotTo(HaveOccurred())
+
+		By("registering the type in the Scheme")
+		builder := scheme.Builder{GroupVersion: testDefaulterGVK.GroupVersion()}
+		builder.Register(&TestDefaulter{}, &TestDefaulterList{})
+		err = builder.AddToScheme(m.GetScheme())
+		ExpectWithOffset(1, err).NotTo(HaveOccurred())
+
+		err = WebhookManagedBy(m).
+			WithMutatorFactory(mutatorFactoryForTestDefaulter(m.GetScheme())).
+			For(&TestDefaulter{}).
+			WithLogConstructor(func(base logr.Logger, req *admission.Request) logr.Logger {
+				return admission.DefaultLogConstructor(testingLogger, req)
+			}).
+			Complete()
+		ExpectWithOffset(1, err).NotTo(HaveOccurred())
+		svr := m.GetWebhookServer()
+		ExpectWithOffset(1, svr).NotTo(BeNil())
+
+		reader := strings.NewReader(admissionReviewGV + admissionReviewVersion + `",
+  "request":{
+    "uid":"07e52e8d-4513-11e9-a716-42010a800270",
+    "kind":{
+      "group":"foo.test.org",
+      "version":"v1",
+      "kind":"TestDefaulter"
+    },
+    "resource":{
+      "group":"foo.test.org",
+      "version":"v1",
+      "resource":"testdefaulter"
+    },
+    "namespace":"default",
+    "name":"foo",
+    "operation":"CREATE",
+    "object":{
+      "replica":1
+    },
+    "oldObject":null
+  }
+}`)
+
+		ctx, cancel := context.WithCancel(context.Background())
+		cancel()
+		err = svr.Start(ctx)
+		if err != nil && !os.IsNotExist(err) {
+			ExpectWithOffset(1, err).NotTo(HaveOccurred())
+		}
+
+		By("sending a request to a mutating webhook path")
+		path := generateMutatePath(testDefaulterGVK)
+		req := httptest.NewRequest("POST", svcBaseAddr+path, reader)
+		req.Header.Add("Content-Type", "application/json")
+		w := httptest.NewRecorder()
+		svr.WebhookMux().ServeHTTP(w, req)
+		ExpectWithOffset(1, w.Code).To(Equal(http.StatusOK))
+		By("sanity checking the response contains reasonable fields")
+		ExpectWithOffset(1, w.Body).To(ContainSubstring(`"allowed":true`))
+		ExpectWithOffset(1, w.Body).To(ContainSubstring(`"patch":`))
+		ExpectWithOffset(1, w.Body).To(ContainSubstring(`"code":200`))
+		EventuallyWithOffset(1, logBuffer).Should(gbytes.Say(`"msg":"Defaulting object","object":{"name":"foo","namespace":"default"},"namespace":"default","name":"foo","resource":{"group":"foo.test.org","version":"v1","resource":"testdefaulter"},"user":"","requestID":"07e52e8d-4513-11e9-a716-42010a800270"`))
+
+		By("sending a request to a validating webhook path that doesn't exist")
+		path = generateValidatePath(testDefaulterGVK)
+		_, err = reader.Seek(0, 0)
+		ExpectWithOffset(1, err).NotTo(HaveOccurred())
+		req = httptest.NewRequest("POST", svcBaseAddr+path, reader)
+		req.Header.Add("Content-Type", "application/json")
+		w = httptest.NewRecorder()
+		svr.WebhookMux().ServeHTTP(w, req)
+		ExpectWithOffset(1, w.Code).To(Equal(http.StatusNotFound))
+	})
+
 	It("should scaffold a custom validating webhook if the type implements the CustomValidator interface", func() {
 		By("creating a controller manager")
 		m, err := manager.New(cfg, manager.Options{})
@@ -735,6 +811,12 @@ func (*TestCustomDefaulter) Default(ctx context.Context, obj runtime.Object) err
 
 var _ admission.CustomDefaulter = &TestCustomDefaulter{}
 
+func mutatorFactoryForTestDefaulter(scheme *runtime.Scheme) admission.HandlerFactory {
+	return func(obj runtime.Object, _ admission.Decoder) admission.Handler {
+		return admission.WithCustomDefaulter(scheme, obj, &TestCustomDefaulter{}).Handler
+	}
+}
+
 // TestCustomValidator.
 
 type TestCustomValidator struct{}

pkg/webhook/admission/webhook.go

@@ -27,6 +27,7 @@ import (
 	"gomodules.xyz/jsonpatch/v2"
 	admissionv1 "k8s.io/api/admission/v1"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/runtime"
 	"k8s.io/apimachinery/pkg/util/json"
 	utilruntime "k8s.io/apimachinery/pkg/util/runtime"
 	"k8s.io/klog/v2"
@@ -95,6 +96,8 @@ func (r *Response) Complete(req Request) error {
 	return nil
 }
 
+type HandlerFactory func(obj runtime.Object, decoder Decoder) Handler
+
 // Handler can handle an AdmissionRequest.
 type Handler interface {
 	// Handle yields a response to an AdmissionRequest.
@@ -114,6 +117,13 @@ func (f HandlerFunc) Handle(ctx context.Context, req Request) Response {
 	return f(ctx, req)
 }
 
+// WithMutator creates a new Webhook for a handler factory.
+func WithHandlerFactory(scheme *runtime.Scheme, obj runtime.Object, factory HandlerFactory) *Webhook {
+	return &Webhook{
+		Handler: factory(obj, NewDecoder(scheme)),
+	}
+}
+
 // Webhook represents each individual webhook.
 //
 // It must be registered with a webhook.Server or