Do not automatically decode runtime.RawExtension

Make clients opt in to decoding objects that are stored
in the generic api.List object by invoking runtime.DecodeList()
with a set of schemes. Makes it easier to handle unknown
schema objects because decoding is in the control of the code.

Add runtime.Unstructured, which is a simple in memory
representation of an external object.

pkg/runtime/interfaces.go

@@ -16,6 +16,24 @@ limitations under the License.
 
 package runtime
 
+// ObjectScheme represents common conversions between formal external API versions
+// and the internal Go structs. ObjectScheme is typically used with ObjectCodec to
+// transform internal Go structs into serialized versions. There may be many valid
+// ObjectCodecs for each ObjectScheme.
+type ObjectScheme interface {
+	ObjectConvertor
+	ObjectTyper
+	ObjectCreater
+	ObjectCopier
+}
+
+// ObjectCodec represents the common mechanisms for converting to and from a particular
+// binary representation of an object.
+type ObjectCodec interface {
+	ObjectEncoder
+	Decoder
+}
+
 // Decoder defines methods for deserializing API objects into a given type
 type Decoder interface {
 	Decode(data []byte) (Object, error)
@@ -33,6 +51,22 @@ type Codec interface {
 	Encoder
 }
 
+// ObjectCopier duplicates an object.
+type ObjectCopier interface {
+	// Copy returns an exact copy of the provided Object, or an error if the
+	// copy could not be completed.
+	Copy(Object) (Object, error)
+}
+
+// ObjectEncoder turns an object into a byte array. This interface is a
+// general form of the Encoder interface
+type ObjectEncoder interface {
+	// EncodeToVersion convert and serializes an object in the internal format
+	// to a specified output version. An error is returned if the object
+	// cannot be converted for any reason.
+	EncodeToVersion(obj Object, outVersion string) ([]byte, error)
+}
+
 // ObjectConvertor converts an object to a different version.
 type ObjectConvertor interface {
 	Convert(in, out interface{}) error
@@ -43,8 +77,17 @@ type ObjectConvertor interface {
 // ObjectTyper contains methods for extracting the APIVersion and Kind
 // of objects.
 type ObjectTyper interface {
+	// DataVersionAndKind returns the version and kind of the provided data, or an error
+	// if another problem is detected. In many cases this method can be as expensive to
+	// invoke as the Decode method.
 	DataVersionAndKind([]byte) (version, kind string, err error)
+	// ObjectVersionAndKind returns the version and kind of the provided object, or an
+	// error if the object is not recognized (IsNotRegisteredError will return true).
 	ObjectVersionAndKind(Object) (version, kind string, err error)
+	// Recognizes returns true if the scheme is able to handle the provided version and kind,
+	// or more precisely that the provided version is a possible conversion or decoding
+	// target.
+	Recognizes(version, kind string) bool
 }
 
 // ObjectCreater contains methods for instantiating an object by kind and version.
@@ -52,6 +95,20 @@ type ObjectCreater interface {
 	New(version, kind string) (out Object, err error)
 }
 
+// ObjectDecoder is a convenience interface for identifying serialized versions of objects
+// and transforming them into Objects. It intentionally overlaps with ObjectTyper and
+// Decoder for use in decode only paths.
+type ObjectDecoder interface {
+	Decoder
+	// DataVersionAndKind returns the version and kind of the provided data, or an error
+	// if another problem is detected. In many cases this method can be as expensive to
+	// invoke as the Decode method.
+	DataVersionAndKind([]byte) (version, kind string, err error)
+	// Recognizes returns true if the scheme is able to handle the provided version and kind
+	// of an object.
+	Recognizes(version, kind string) bool
+}
+
 // ResourceVersioner provides methods for setting and retrieving
 // the resource version from an API object.
 type ResourceVersioner interface {