default kubernetes agent for generated clients

Set default kubernetes agent if empty

staging/src/k8s.io/client-go/kubernetes_test/clientset_test.go

@@ -0,0 +1,88 @@
+/*
+Copyright 2022 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 kubernetes_test
+
+import (
+	"context"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	v1 "k8s.io/api/core/v1"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/client-go/kubernetes"
+	"k8s.io/client-go/kubernetes/scheme"
+	"k8s.io/client-go/rest"
+)
+
+func TestClientUserAgent(t *testing.T) {
+	tests := []struct {
+		name      string
+		userAgent string
+		expect    string
+	}{
+		{
+			name:   "empty",
+			expect: rest.DefaultKubernetesUserAgent(),
+		},
+		{
+			name:      "custom",
+			userAgent: "test-agent",
+			expect:    "test-agent",
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			ts := httptest.NewUnstartedServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+				userAgent := r.Header.Get("User-Agent")
+				if userAgent != tc.expect {
+					t.Errorf("User Agent expected: %s got: %s", tc.expect, userAgent)
+					http.Error(w, "Unexpected user agent", http.StatusBadRequest)
+					return
+				}
+				w.Header().Set("Content-Type", "application/json")
+				w.Write([]byte("{}"))
+			}))
+			ts.Start()
+			defer ts.Close()
+
+			gv := v1.SchemeGroupVersion
+			config := &rest.Config{
+				Host: ts.URL,
+			}
+			config.GroupVersion = &gv
+			config.NegotiatedSerializer = scheme.Codecs.WithoutConversion()
+			config.UserAgent = tc.userAgent
+			config.ContentType = "application/json"
+
+			client, err := kubernetes.NewForConfig(config)
+			if err != nil {
+				t.Fatalf("failed to create REST client: %v", err)
+			}
+			_, err = client.CoreV1().Pods("").List(context.TODO(), metav1.ListOptions{})
+			if err != nil {
+				t.Error(err)
+			}
+			_, err = client.CoreV1().Secrets("").List(context.TODO(), metav1.ListOptions{})
+			if err != nil {
+				t.Error(err)
+			}
+		})
+	}
+
+}

staging/src/k8s.io/code-generator/cmd/client-gen/generators/generator_for_clientset.go

@@ -143,6 +143,10 @@ var newClientsetForConfigTemplate = `
 func NewForConfig(c *$.Config|raw$) (*Clientset, error) {
 	configShallowCopy := *c
 
+	if configShallowCopy.UserAgent == "" {
+		configShallowCopy.UserAgent = $.DefaultKubernetesUserAgent|raw$()
+	}
+
 	// share the transport between all clients
 	httpClient, err := $.RESTHTTPClientFor|raw$(&configShallowCopy)
 	if err != nil {