Remove extraneous decoder interface

We don't have anywhere that we actually make use of decoder as an
interface, so switch to just have a concrete implementation.

Author: DirectXMan12

pkg/webhook/admission/decode.go

@@ -21,27 +21,19 @@ import (
 	"k8s.io/apimachinery/pkg/runtime/serializer"
 )
 
-// DecodeFunc is a function that implements an admission decoder in a single function.
-type DecodeFunc func(Request, runtime.Object) error
-
-var _ Decoder = DecodeFunc(nil)
-
-// Decode implements the Decoder interface.
-func (f DecodeFunc) Decode(req Request, obj runtime.Object) error {
-	return f(req, obj)
-}
-
-type decoder struct {
+// Decoder knows how to decode the contents of an admission
+// request into a concrete object.
+type Decoder struct {
 	codecs serializer.CodecFactory
 }
 
 // NewDecoder creates a Decoder given the runtime.Scheme
-func NewDecoder(scheme *runtime.Scheme) (Decoder, error) {
-	return decoder{codecs: serializer.NewCodecFactory(scheme)}, nil
+func NewDecoder(scheme *runtime.Scheme) (*Decoder, error) {
+	return &Decoder{codecs: serializer.NewCodecFactory(scheme)}, nil
 }
 
 // Decode decodes the inlined object in the AdmissionRequest into the passed-in runtime.Object.
-func (d decoder) Decode(req Request, into runtime.Object) error {
+func (d *Decoder) Decode(req Request, into runtime.Object) error {
 	deserializer := d.codecs.UniversalDeserializer()
 	return runtime.DecodeInto(deserializer, req.AdmissionRequest.Object.Raw, into)
 }

pkg/webhook/admission/decode_test.go

@@ -27,7 +27,7 @@ import (
 )
 
 var _ = Describe("admission webhook decoder", func() {
-	var decoder Decoder
+	var decoder *Decoder
 	BeforeEach(func(done Done) {
 		var err error
 		decoder, err = NewDecoder(scheme.Scheme)

pkg/webhook/admission/types.go

@@ -20,7 +20,6 @@ import (
 	"github.com/appscode/jsonpatch"
 
 	admissionv1beta1 "k8s.io/api/admission/v1beta1"
-	"k8s.io/apimachinery/pkg/runtime"
 )
 
 // Request defines the input for an admission handler.
@@ -46,12 +45,6 @@ type Response struct {
 	admissionv1beta1.AdmissionResponse
 }
 
-// Decoder is used to decode AdmissionRequest.
-type Decoder interface {
-	// Decode decodes the raw byte object from the AdmissionRequest to the passed-in runtime.Object.
-	Decode(Request, runtime.Object) error
-}
-
 // WebhookType defines the type of an admission webhook
 // (validating or mutating).
 type WebhookType int