Add a lazy discovery interface for Unstructured

Delays the error until the first call and then preserves it for others.
More closely matches the intent of the Object() calls. Loaders are now
lazy and don't need to return errors directly.

Sets the stage for collapsing unstructured and structured builders
together.

Kubernetes-commit: e298aa39c3de8ad1059861b7f78d62005ca87f88

discovery/unstructured.go

@@ -17,22 +17,28 @@ limitations under the License.
 package discovery
 
 import (
-	"fmt"
+	"reflect"
 
 	"k8s.io/apimachinery/pkg/runtime"
 	"k8s.io/apimachinery/pkg/runtime/schema"
 )
 
-// UnstructuredObjectTyper provides a runtime.ObjectTyper implmentation for
+// UnstructuredObjectTyper provides a runtime.ObjectTyper implementation for
 // runtime.Unstructured object based on discovery information.
 type UnstructuredObjectTyper struct {
 	registered map[schema.GroupVersionKind]bool
+	typers     []runtime.ObjectTyper
 }
 
 // NewUnstructuredObjectTyper returns a runtime.ObjectTyper for
-// unstructred objects based on discovery information.
-func NewUnstructuredObjectTyper(groupResources []*APIGroupResources) *UnstructuredObjectTyper {
-	dot := &UnstructuredObjectTyper{registered: make(map[schema.GroupVersionKind]bool)}
+// unstructured objects based on discovery information. It accepts a list of fallback typers
+// for handling objects that are not runtime.Unstructured. It does not delegate the Recognizes
+// check, only ObjectKinds.
+func NewUnstructuredObjectTyper(groupResources []*APIGroupResources, typers ...runtime.ObjectTyper) *UnstructuredObjectTyper {
+	dot := &UnstructuredObjectTyper{
+		registered: make(map[schema.GroupVersionKind]bool),
+		typers:     typers,
+	}
 	for _, group := range groupResources {
 		for _, discoveryVersion := range group.Group.Versions {
 			resources, ok := group.VersionedResources[discoveryVersion.Version]
@@ -55,17 +61,29 @@ func NewUnstructuredObjectTyper(groupResources []*APIGroupResources) *Unstructur
 // because runtime.Unstructured object should always have group,version,kind
 // information set.
 func (d *UnstructuredObjectTyper) ObjectKinds(obj runtime.Object) (gvks []schema.GroupVersionKind, unversionedType bool, err error) {
-	if _, ok := obj.(runtime.Unstructured); !ok {
-		return nil, false, fmt.Errorf("type %T is invalid for dynamic object typer", obj)
+	if _, ok := obj.(runtime.Unstructured); ok {
+		gvk := obj.GetObjectKind().GroupVersionKind()
+		if len(gvk.Kind) == 0 {
+			return nil, false, runtime.NewMissingKindErr("object has no kind field ")
+		}
+		if len(gvk.Version) == 0 {
+			return nil, false, runtime.NewMissingVersionErr("object has no apiVersion field")
+		}
+		return []schema.GroupVersionKind{gvk}, false, nil
 	}
-	gvk := obj.GetObjectKind().GroupVersionKind()
-	if len(gvk.Kind) == 0 {
-		return nil, false, runtime.NewMissingKindErr("unstructured object has no kind")
+	var lastErr error
+	for _, typer := range d.typers {
+		gvks, unversioned, err := typer.ObjectKinds(obj)
+		if err != nil {
+			lastErr = err
+			continue
+		}
+		return gvks, unversioned, nil
 	}
-	if len(gvk.Version) == 0 {
-		return nil, false, runtime.NewMissingVersionErr("unstructured object has no version")
+	if lastErr == nil {
+		lastErr = runtime.NewNotRegisteredErrForType(reflect.TypeOf(obj))
 	}
-	return []schema.GroupVersionKind{gvk}, false, nil
+	return nil, false, lastErr
 }
 
 // Recognizes returns true if the provided group,version,kind was in the

dynamic/dynamic_util.go

@@ -84,7 +84,7 @@ func NewObjectTyper(resources []*metav1.APIResourceList) (runtime.ObjectTyper, e
 // information.
 func (ot *ObjectTyper) ObjectKinds(obj runtime.Object) ([]schema.GroupVersionKind, bool, error) {
 	if _, ok := obj.(*unstructured.Unstructured); !ok {
-		return nil, false, fmt.Errorf("type %T is invalid for dynamic object typer", obj)
+		return nil, false, fmt.Errorf("type %T is invalid for determining dynamic object types", obj)
 	}
 	return []schema.GroupVersionKind{obj.GetObjectKind().GroupVersionKind()}, false, nil
 }