Add structured alternatives to strings in client-go/tools/cache

Kubernetes-commit: ec9515a828ec3907ffc66913947adf4e8ee7b9d6

tools/cache/keyfunc.go

@@ -0,0 +1,50 @@
+/*
+Copyright 2023 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package cache
+
+// ObjectName is a reference to an object of some implicit kind
+type ObjectName struct {
+	Namespace string
+	Name      string
+}
+
+// NewObjectName constructs a new one
+func NewObjectName(namespace, name string) ObjectName {
+	return ObjectName{Namespace: namespace, Name: name}
+}
+
+// Parts is the inverse of the constructor
+func (objName ObjectName) Parts() (namespace, name string) {
+	return objName.Namespace, objName.Name
+}
+
+// String returns the standard string encoding,
+// which is designed to match the historical behavior of MetaNamespaceKeyFunc.
+func (objName ObjectName) String() string {
+	if len(objName.Namespace) > 0 {
+		return objName.Namespace + "/" + objName.Name
+	}
+	return objName.Name
+}
+
+// ParseObjectName tries to parse the standard encoding
+func ParseObjectName(str string) (ObjectName, error) {
+	var objName ObjectName
+	var err error
+	objName.Namespace, objName.Name, err = SplitMetaNamespaceKey(str)
+	return objName, err
+}

tools/cache/store.go

@@ -21,6 +21,7 @@ import (
 	"strings"
 
 	"k8s.io/apimachinery/pkg/api/meta"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 )
 
 // Store is a generic object storage and processing interface.  A
@@ -99,20 +100,38 @@ type ExplicitKey string
 // The key uses the format <namespace>/<name> unless <namespace> is empty, then
 // it's just <name>.
 //
-// TODO: replace key-as-string with a key-as-struct so that this
+// Clients that want a structured alternative can use ObjectToName or MetaObjectToName.
-// packing/unpacking won't be necessary.
+// Note: this would not be a client that wants a key for a Store because those are
+// necessarily strings.
+//
+// TODO maybe some day?: change Store to be keyed differently
 func MetaNamespaceKeyFunc(obj interface{}) (string, error) {
 	if key, ok := obj.(ExplicitKey); ok {
 		return string(key), nil
 	}
+	objName, err := ObjectToName(obj)
+	if err != nil {
+		return "", err
+	}
+	return objName.String(), nil
+}
+
+// ObjectToName returns the structured name for the given object,
+// if indeed it can be viewed as a metav1.Object.
+func ObjectToName(obj interface{}) (ObjectName, error) {
 	meta, err := meta.Accessor(obj)
 	if err != nil {
-		return "", fmt.Errorf("object has no meta: %v", err)
+		return ObjectName{}, fmt.Errorf("object has no meta: %v", err)
 	}
-	if len(meta.GetNamespace()) > 0 {
+	return MetaObjectToName(meta), nil
-		return meta.GetNamespace() + "/" + meta.GetName(), nil
+}
+
+// MetaObjectToName returns the structured name for the given object
+func MetaObjectToName(obj metav1.Object) ObjectName {
+	if len(obj.GetNamespace()) > 0 {
+		return ObjectName{Namespace: obj.GetNamespace(), Name: obj.GetName()}
 	}
-	return meta.GetName(), nil
+	return ObjectName{Namespace: "", Name: obj.GetName()}
 }
 
 // SplitMetaNamespaceKey returns the namespace and name that