Add TypeAccessor to api/meta for objects without Object/ListMeta

Adding objects that have TypeMeta (use runtime.Scheme) but do not
expose ObjectMeta/ListMeta (because they are not Kube API objects)
and wanted to get the simpler access path for in memory objects.

pkg/api/meta/interfaces.go

@@ -32,17 +32,16 @@ type VersionInterfaces struct {
 // internal API objects. Attempting to set or retrieve a field on an object that does
 // not support that field (Name, UID, Namespace on lists) will be a no-op and return
 // a default value.
+// TODO: rename to ObjectInterface when we clear up these interfaces.
 type Interface interface {
+	TypeInterface
+
 	Namespace() string
 	SetNamespace(namespace string)
 	Name() string
 	SetName(name string)
 	UID() types.UID
 	SetUID(uid types.UID)
-	APIVersion() string
-	SetAPIVersion(version string)
-	Kind() string
-	SetKind(kind string)
 	ResourceVersion() string
 	SetResourceVersion(version string)
 	SelfLink() string
@@ -53,6 +52,14 @@ type Interface interface {
 	SetAnnotations(annotations map[string]string)
 }
 
+// TypeInterface exposes the type and APIVersion of versioned or internal API objects.
+type TypeInterface interface {
+	APIVersion() string
+	SetAPIVersion(version string)
+	Kind() string
+	SetKind(kind string)
+}
+
 // MetadataAccessor lets you work with object and list metadata from any of the versioned or
 // internal API objects. Attempting to set or retrieve a field on an object that does
 // not support that field (Name, UID, Namespace on lists) will be a no-op and return

pkg/api/meta/meta.go

@@ -74,6 +74,32 @@ func Accessor(obj interface{}) (Interface, error) {
 	return a, nil
 }
 
+// TypeAccessor returns an interface that allows retrieving and modifying the APIVersion
+// and Kind of an in-memory internal object.
+// TODO: this interface is used to test code that does not have ObjectMeta or ListMeta
+// in round tripping (objects which can use apiVersion/kind, but do not fit the Kube
+// api conventions).
+func TypeAccessor(obj interface{}) (TypeInterface, error) {
+	v, err := conversion.EnforcePtr(obj)
+	if err != nil {
+		return nil, err
+	}
+	t := v.Type()
+	if v.Kind() != reflect.Struct {
+		return nil, fmt.Errorf("expected struct, but got %v: %v (%#v)", v.Kind(), t, v.Interface())
+	}
+
+	typeMeta := v.FieldByName("TypeMeta")
+	if !typeMeta.IsValid() {
+		return nil, fmt.Errorf("struct %v lacks embedded TypeMeta type", t)
+	}
+	a := &genericAccessor{}
+	if err := extractFromTypeMeta(typeMeta, a); err != nil {
+		return nil, fmt.Errorf("unable to find type fields on %#v: %v", typeMeta, err)
+	}
+	return a, nil
+}
+
 // NewAccessor returns a MetadataAccessor that can retrieve
 // or manipulate resource version on objects derived from core API
 // metadata concepts.

pkg/api/meta/meta_test.go

@@ -79,6 +79,17 @@ func TestGenericTypeMeta(t *testing.T) {
 		t.Errorf("expected %v, got %v", e, a)
 	}
 
+	typeAccessor, err := TypeAccessor(&j)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if e, a := "a", accessor.APIVersion(); e != a {
+		t.Errorf("expected %v, got %v", e, a)
+	}
+	if e, a := "b", accessor.Kind(); e != a {
+		t.Errorf("expected %v, got %v", e, a)
+	}
+
 	accessor.SetNamespace("baz")
 	accessor.SetName("bar")
 	accessor.SetUID("other")
@@ -109,6 +120,15 @@ func TestGenericTypeMeta(t *testing.T) {
 	if e, a := "google.com", j.SelfLink; e != a {
 		t.Errorf("expected %v, got %v", e, a)
 	}
+
+	typeAccessor.SetAPIVersion("d")
+	typeAccessor.SetKind("e")
+	if e, a := "d", j.APIVersion; e != a {
+		t.Errorf("expected %v, got %v", e, a)
+	}
+	if e, a := "e", j.Kind; e != a {
+		t.Errorf("expected %v, got %v", e, a)
+	}
 }
 
 type InternalTypeMeta struct {

pkg/api/serialization_test.go

@@ -163,7 +163,7 @@ func fuzzerFor(t *testing.T, version string, src rand.Source) *fuzz.Fuzzer {
 func fuzzInternalObject(t *testing.T, forVersion string, item runtime.Object, seed int64) runtime.Object {
 	fuzzerFor(t, forVersion, rand.NewSource(seed)).Fuzz(item)
 
-	j, err := meta.Accessor(item)
+	j, err := meta.TypeAccessor(item)
 	if err != nil {
 		t.Fatalf("Unexpected error %v for %#v", err, item)
 	}
@@ -264,7 +264,7 @@ func TestRoundTripTypes(t *testing.T) {
 			if err != nil {
 				t.Fatalf("Couldn't make a %v? %v", kind, err)
 			}
-			if _, err := meta.Accessor(item); err != nil {
+			if _, err := meta.TypeAccessor(item); err != nil {
 				t.Fatalf("%q is not a TypeMeta and cannot be tested - add it to nonRoundTrippableTypes: %v", kind, err)
 			}
 			roundTripSame(t, item)

pkg/runtime/scheme.go

@@ -360,6 +360,9 @@ func (s *Scheme) Decode(data []byte) (Object, error) {
 // pointer to an api type.
 // If obj's APIVersion doesn't match that in data, an attempt will be made to convert
 // data into obj's version.
+// TODO: allow Decode/DecodeInto to take a default apiVersion and a default kind, to
+// be applied if the provided object does not have either field (integrate external
+// apis into the decoding scheme).
 func (s *Scheme) DecodeInto(data []byte, obj Object) error {
 	return s.raw.DecodeInto(data, obj)
 }