✨ support decoding the old object in an AdmissionRequest

Author: Mengqi Yu

example/mutatingwebhook.go

@@ -36,7 +36,7 @@ type podAnnotator struct {
 func (a *podAnnotator) Handle(ctx context.Context, req admission.Request) admission.Response {
 	pod := &corev1.Pod{}
 
-	err := a.decoder.Decode(req, pod)
+	err := a.decoder.Decode(req.Object, pod)
 	if err != nil {
 		return admission.Errored(http.StatusBadRequest, err)
 	}
@@ -51,7 +51,7 @@ func (a *podAnnotator) Handle(ctx context.Context, req admission.Request) admiss
 		return admission.Errored(http.StatusInternalServerError, err)
 	}
 
-	return admission.PatchResponseFromRaw(req.AdmissionRequest.Object.Raw, marshaledPod)
+	return admission.PatchResponseFromRaw(req.Object.Raw, marshaledPod)
 }
 
 // podAnnotator implements inject.Client.
@@ -63,7 +63,7 @@ func (a *podAnnotator) InjectClient(c client.Client) error {
 	return nil
 }
 
-// podAnnotator implements inject.Decoder.
+// podAnnotator implements admission.DecoderInjector.
 // A decoder will be automatically injected.
 
 // InjectDecoder injects the decoder.

example/validatingwebhook.go

@@ -36,7 +36,7 @@ type podValidator struct {
 func (v *podValidator) Handle(ctx context.Context, req admission.Request) admission.Response {
 	pod := &corev1.Pod{}
 
-	err := v.decoder.Decode(req, pod)
+	err := v.decoder.Decode(req.Object, pod)
 	if err != nil {
 		return admission.Errored(http.StatusBadRequest, err)
 	}
@@ -62,7 +62,7 @@ func (v *podValidator) InjectClient(c client.Client) error {
 	return nil
 }
 
-// podValidator implements inject.Decoder.
+// podValidator implements admission.DecoderInjector.
 // A decoder will be automatically injected.
 
 // InjectDecoder injects the decoder.

pkg/webhook/admission/decode.go

@@ -35,7 +35,13 @@ func NewDecoder(scheme *runtime.Scheme) (*Decoder, error) {
 }
 
 // Decode decodes the inlined object in the AdmissionRequest into the passed-in runtime.Object.
+// If you want decode the OldObject in the AdmissionRequest, use DecodeRaw.
 func (d *Decoder) Decode(req Request, into runtime.Object) error {
+	return d.DecodeRaw(req.Object, into)
+}
+
+// DecodeRaw decodes a RawExtension object into the passed-in runtime.Object.
+func (d *Decoder) DecodeRaw(rawObj runtime.RawExtension, into runtime.Object) error {
 	// NB(directxman12): there's a bug/weird interaction between decoders and
 	// the API server where the API server doesn't send a GVK on the embedded
 	// objects, which means the unstructured decoder refuses to decode.  It
@@ -45,13 +51,13 @@ func (d *Decoder) Decode(req Request, into runtime.Object) error {
 	// See kubernetes/kubernetes#74373.
 	if unstructuredInto, isUnstructured := into.(*unstructured.Unstructured); isUnstructured {
 		// unmarshal into unstructured's underlying object to avoid calling the decoder
-		if err := json.Unmarshal(req.Object.Raw, &unstructuredInto.Object); err != nil {
+		if err := json.Unmarshal(rawObj.Raw, &unstructuredInto.Object); err != nil {
 			return err
 		}
 
 		return nil
 	}
 
 	deserializer := d.codecs.UniversalDeserializer()
-	return runtime.DecodeInto(deserializer, req.AdmissionRequest.Object.Raw, into)
+	return runtime.DecodeInto(deserializer, rawObj.Raw, into)
 }