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/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