From 51beeb26762d7debd9063aea82967ad583f31184 Mon Sep 17 00:00:00 2001
From: Lukasz Szaszkiewicz <lukasz.szaszkiewicz@gmail.com>
Date: Tue, 28 Oct 2025 09:40:01 +0100
Subject: [PATCH] dynamic-resource-allocation/client: expose
 IsWatchListSemanticsUnSupported

---
 .../client/client.go                          | 12 ++++
 .../client/client_test.go                     | 55 +++++++++++++++++++
 2 files changed, 67 insertions(+)
 create mode 100644 staging/src/k8s.io/dynamic-resource-allocation/client/client_test.go

diff --git a/staging/src/k8s.io/dynamic-resource-allocation/client/client.go b/staging/src/k8s.io/dynamic-resource-allocation/client/client.go
index 9a02424b0ad..43676d5d258 100644
--- a/staging/src/k8s.io/dynamic-resource-allocation/client/client.go
+++ b/staging/src/k8s.io/dynamic-resource-allocation/client/client.go
@@ -23,6 +23,7 @@ import (
 	"k8s.io/client-go/kubernetes"
 	cgoresource "k8s.io/client-go/kubernetes/typed/resource/v1"
 	rest "k8s.io/client-go/rest"
+	"k8s.io/client-go/util/watchlist"
 )
 
 // Enumerate all supported APIs, most preferred first.
@@ -102,3 +103,14 @@ func (c *Client) ResourceSlices() cgoresource.ResourceSliceInterface {
 		c.clientSet.ResourceV1beta2().ResourceSlices(),
 	)
 }
+
+// IsWatchListSemanticsSupported informs the reflector that this client
+// doesn't support WatchList semantics.
+//
+// This is a synthetic method whose sole purpose is to satisfy the optional
+// interface check performed by the reflector.
+// Returning true signals that WatchList can NOT be used.
+// No additional logic is implemented here.
+func (c *Client) IsWatchListSemanticsUnSupported() bool {
+	return watchlist.DoesClientNotSupportWatchListSemantics(c.clientSet)
+}
diff --git a/staging/src/k8s.io/dynamic-resource-allocation/client/client_test.go b/staging/src/k8s.io/dynamic-resource-allocation/client/client_test.go
new file mode 100644
index 00000000000..c8ec55ecdb2
--- /dev/null
+++ b/staging/src/k8s.io/dynamic-resource-allocation/client/client_test.go
@@ -0,0 +1,55 @@
+/*
+Copyright 2025 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 client
+
+import (
+	"testing"
+
+	"k8s.io/client-go/kubernetes"
+	"k8s.io/client-go/kubernetes/fake"
+	restclient "k8s.io/client-go/rest"
+	"k8s.io/client-go/util/watchlist"
+)
+
+func TestDoesClientSupportWatchListSemantics(t *testing.T) {
+	scenarios := []struct {
+		name                                           string
+		clientSet                                      kubernetes.Interface
+		expectedDoesClientNotSupportWatchListSemantics bool
+	}{
+		{
+			name:      "DR with real kube client supports WatchList semantics",
+			clientSet: kubernetes.NewForConfigOrDie(&restclient.Config{}),
+			expectedDoesClientNotSupportWatchListSemantics: false,
+		},
+		{
+			name:      "DR with fake kube client does NOT support WatchList semantics",
+			clientSet: fake.NewClientset(),
+			expectedDoesClientNotSupportWatchListSemantics: true,
+		},
+	}
+
+	for _, scenario := range scenarios {
+		t.Run(scenario.name, func(t *testing.T) {
+			target := New(scenario.clientSet)
+			actual := watchlist.DoesClientNotSupportWatchListSemantics(target)
+			if actual != scenario.expectedDoesClientNotSupportWatchListSemantics {
+				t.Fatalf("watchlist.DoesClientNotSupportWatchListSemantics, got: %v, want: %v", actual, scenario.expectedDoesClientNotSupportWatchListSemantics)
+			}
+		})
+	}
+}