fed: Add type adapter registration to simplify maintenance

federation/pkg/typeadapters/adapter.go

@@ -17,6 +17,8 @@ limitations under the License.
 package typeadapters
 
 import (
+	"fmt"
+
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	pkgruntime "k8s.io/apimachinery/pkg/runtime"
 	"k8s.io/apimachinery/pkg/types"
@@ -29,8 +31,6 @@ import (
 // federated type.  Code written to this interface can then target any
 // type for which an implementation of this interface exists.
 type FederatedTypeAdapter interface {
-	SetClient(client federationclientset.Interface)
-
 	Kind() string
 	ObjectType() pkgruntime.Object
 	IsExpectedType(obj interface{}) bool
@@ -57,3 +57,35 @@ type FederatedTypeAdapter interface {
 
 	NewTestObject(namespace string) pkgruntime.Object
 }
+
+// AdapterFactory defines the function signature for factory methods
+// that create FederatedTypeAdapters.  Such methods should be
+// registered with RegisterAdapterFactory to ensure the type adapter
+// is discoverable.
+type AdapterFactory func(client federationclientset.Interface) FederatedTypeAdapter
+
+var typeAdapterRegistry = make(map[string]AdapterFactory)
+
+// RegisterAdapterFactory ensures that the given kind and adapter
+// factory will be returned in the results of the AdapterFactories
+// method.
+func RegisterAdapterFactory(kind string, factory AdapterFactory) {
+	_, ok := typeAdapterRegistry[kind]
+	if ok {
+		// TODO Is panicking ok given that this is part of a type-registration mechanism
+		panic(fmt.Sprintf("An adapter has already been registered for federated type %q", kind))
+	}
+	typeAdapterRegistry[kind] = factory
+}
+
+// AdapterFactories returns a mapping of federated kind
+// (e.g. "secret") to the factory method that will create an adapter
+// for that type.
+func AdapterFactories() map[string]AdapterFactory {
+	// Return a copy to avoid accidental mutation
+	result := make(map[string]AdapterFactory)
+	for key, value := range typeAdapterRegistry {
+		result[key] = value
+	}
+	return result
+}

federation/pkg/typeadapters/secret.go

@@ -27,20 +27,22 @@ import (
 	kubeclientset "k8s.io/kubernetes/pkg/client/clientset_generated/clientset"
 )
 
+const secretKind = "secret"
+
+func init() {
+	RegisterAdapterFactory(secretKind, NewSecretAdapter)
+}
+
 type SecretAdapter struct {
 	client federationclientset.Interface
 }
 
-func NewSecretAdapter(client federationclientset.Interface) *SecretAdapter {
+func NewSecretAdapter(client federationclientset.Interface) FederatedTypeAdapter {
 	return &SecretAdapter{client: client}
 }
 
-func (a *SecretAdapter) SetClient(client federationclientset.Interface) {
-	a.client = client
-}
-
 func (a *SecretAdapter) Kind() string {
-	return "secret"
+	return secretKind
 }
 
 func (a *SecretAdapter) ObjectType() pkgruntime.Object {

test/integration/federation/framework/secret.go

@@ -26,7 +26,7 @@ import (
 )
 
 type SecretFixture struct {
-	adapter  *typeadapters.SecretAdapter
+	adapter  typeadapters.FederatedTypeAdapter
 	stopChan chan struct{}
 }