Allow to wire an object mutation handler

pkg/builder/webhook.go

@@ -37,6 +37,7 @@ import (
 // WebhookBuilder builds a Webhook.
 type WebhookBuilder struct {
 	apiType         runtime.Object
+	mutationHandler admission.ObjectHandler
 	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) WithMutationHandler(handler admission.ObjectHandler) *WebhookBuilder {
+	blder.mutationHandler = handler
+	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
@@ -169,24 +176,24 @@ 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 handler := blder.mutationHandler; handler != nil {
+		w = admission.WithObjectHandler(blder.mgr.GetScheme(), blder.apiType, handler)
+	} else if defaulter := blder.customDefaulter; defaulter != nil {
+		w = admission.WithCustomDefaulter(blder.mgr.GetScheme(), blder.apiType, defaulter)
+	} else if defaulter, ok := blder.apiType.(admission.Defaulter); ok {
+		w = admission.DefaultingWebhookFor(blder.mgr.GetScheme(), defaulter)
 	}
-	if defaulter, ok := blder.apiType.(admission.Defaulter); ok {
-		w := admission.DefaultingWebhookFor(blder.mgr.GetScheme(), defaulter)
-		if blder.recoverPanic != nil {
-			w = w.WithRecoverPanic(*blder.recoverPanic)
-		}
-		return w
+	if w == nil {
+		log.Info(
+			"Skip registering a mutating webhook, object does not implement admission.Defaulter or WithDefaulter wasn't called",
+			"GVK", blder.gvk)
+		return nil
 	}
-	log.Info(
-		"skip registering a mutating webhook, object does not implement admission.Defaulter or WithDefaulter wasn't called",
-		"GVK", blder.gvk)
-	return nil
+	if blder.recoverPanic != nil {
+		w = w.WithRecoverPanic(*blder.recoverPanic)
+	}
+	return w
 }
 
 // registerValidatingWebhook registers a validating webhook if necessary.

pkg/webhook/admission/defaulter_custom.go

@@ -28,6 +28,18 @@ import (
 	"k8s.io/apimachinery/pkg/runtime"
 )
 
+// ObjectHandler defines functions for handling objects on webhooks.
+type ObjectHandler interface {
+	Handle(ctx context.Context, raw []byte, obj runtime.Object) Response
+}
+
+// WithObjectHandler creates a new Webhook for an ObjectHandler interface.
+func WithObjectHandler(scheme *runtime.Scheme, obj runtime.Object, handler ObjectHandler) *Webhook {
+	return &Webhook{
+		Handler: &handlerForType{object: obj, handler: handler, decoder: NewDecoder(scheme)},
+	}
+}
+
 // CustomDefaulter defines functions for setting defaults on resources.
 type CustomDefaulter interface {
 	Default(ctx context.Context, obj runtime.Object) error
@@ -36,22 +48,22 @@ type CustomDefaulter interface {
 // WithCustomDefaulter creates a new Webhook for a CustomDefaulter interface.
 func WithCustomDefaulter(scheme *runtime.Scheme, obj runtime.Object, defaulter CustomDefaulter) *Webhook {
 	return &Webhook{
-		Handler: &defaulterForType{object: obj, defaulter: defaulter, decoder: NewDecoder(scheme)},
+		Handler: &handlerForType{object: obj, handler: &handlerForDefaulter{defaulter: defaulter}, decoder: NewDecoder(scheme)},
 	}
 }
 
-type defaulterForType struct {
-	defaulter CustomDefaulter
-	object    runtime.Object
-	decoder   Decoder
+type handlerForType struct {
+	handler ObjectHandler
+	object  runtime.Object
+	decoder Decoder
 }
 
 // Handle handles admission requests.
-func (h *defaulterForType) Handle(ctx context.Context, req Request) Response {
+func (h *handlerForType) Handle(ctx context.Context, req Request) Response {
 	if h.decoder == nil {
 		panic("decoder should never be nil")
 	}
-	if h.defaulter == nil {
+	if h.handler == nil {
 		panic("defaulter should never be nil")
 	}
 	if h.object == nil {
@@ -76,7 +88,14 @@ func (h *defaulterForType) Handle(ctx context.Context, req Request) Response {
 		return Errored(http.StatusBadRequest, err)
 	}
 
-	// Default the object
+	return h.handler.Handle(ctx, req.Object.Raw, obj)
+}
+
+type handlerForDefaulter struct {
+	defaulter CustomDefaulter
+}
+
+func (h *handlerForDefaulter) Handle(ctx context.Context, raw []byte, obj runtime.Object) Response {
 	if err := h.defaulter.Default(ctx, obj); err != nil {
 		var apiStatus apierrors.APIStatus
 		if errors.As(err, &apiStatus) {
@@ -90,5 +109,5 @@ func (h *defaulterForType) Handle(ctx context.Context, req Request) Response {
 	if err != nil {
 		return Errored(http.StatusInternalServerError, err)
 	}
-	return PatchResponseFromRaw(req.Object.Raw, marshalled)
+	return PatchResponseFromRaw(raw, marshalled)
 }