Add integration test for rejecting non-JSON RawExtensions.

The content of a RawExtension isn't constrained on its own, but there is a de facto requirement that
the object in a request body can be converted to unstructured. Currently, a RawExtension can only be
converted to unstructured if its Raw field is nil or if it contains valid JSON.

test/integration/apiserver/unstructured_test.go

@@ -0,0 +1,108 @@
+/*
+Copyright 2024 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 apiserver
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"testing"
+
+	"golang.org/x/net/http2"
+
+	appsv1 "k8s.io/api/apps/v1"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/runtime"
+	appsv1applyconfigurations "k8s.io/client-go/applyconfigurations/apps/v1"
+	clientset "k8s.io/client-go/kubernetes"
+	kubeapiservertesting "k8s.io/kubernetes/cmd/kube-apiserver/app/testing"
+	"k8s.io/kubernetes/test/integration/framework"
+)
+
+// TestRequestObjectConvertibleToUnstructured tests that write requests fail if the request object
+// is not convertible to unstructured. The ability to convert an object to unstructured ensures that
+// it can be encoded as JSON and that field managers can be determined.
+func TestRequestObjectConvertibleToUnstructured(t *testing.T) {
+	server := kubeapiservertesting.StartTestServerOrDie(t, nil, []string{}, framework.SharedEtcd())
+	defer server.TearDownFn()
+
+	for i, raw := range []string{
+		``,
+		`"`,
+		`{`,
+		`[`,
+		`1z`,
+		`z`,
+	} {
+		// The Protobuf request encoding is required. Invalid JSON cannot be embedded in a
+		// JSON object or array without making the containing object or array also invalid.
+		protoConfig := server.ClientConfig
+		protoConfig.ContentConfig.ContentType = runtime.ContentTypeProtobuf
+		protoConfig.ContentConfig.AcceptContentTypes = runtime.ContentTypeProtobuf
+		protoClient, err := clientset.NewForConfig(protoConfig)
+		if err != nil {
+			t.Fatalf("unexpected error creating proto client: %v", err)
+		}
+
+		createError := new(http2.StreamError)
+		if _, err := protoClient.AppsV1().ControllerRevisions("default").Create(context.TODO(), &appsv1.ControllerRevision{
+			ObjectMeta: metav1.ObjectMeta{
+				Name: fmt.Sprintf("test-revision-create-%d", i),
+			},
+			Data: runtime.RawExtension{Raw: []byte(raw)},
+		}, metav1.CreateOptions{}); errors.As(err, createError) && createError.Code == http2.ErrCodeInternal {
+			t.Logf("create returned internal error as expected with rawextension %#v: %v", raw, err)
+		} else {
+			t.Errorf("create returned unexpected error: %#v", err)
+		}
+
+		var marshalerError *json.MarshalerError
+		if _, err := protoClient.AppsV1().ControllerRevisions("default").Apply(context.TODO(), appsv1applyconfigurations.ControllerRevision("test-revision-apply", "default").
+			WithData(runtime.RawExtension{Raw: []byte(raw)}),
+			metav1.ApplyOptions{}); errors.As(err, &marshalerError) {
+			// In this case the error is currently client-side, since apply request
+			// bodies must be encoded as JSON. Included here to cover the future
+			// possibility of Protobuf-encoded apply configurations.
+			t.Logf("apply returned client-side marshaler error as expected with rawextension %#v: %v", raw, err)
+		} else {
+			t.Errorf("apply returned unexpected error: %#v", err)
+		}
+
+		// Create an object to be updated. If the object does not exist, then the update
+		// will short-circuit on "not found" before it encounters the error that is
+		// interesting to this test.
+		existing, err := protoClient.AppsV1().ControllerRevisions("default").Create(context.TODO(), &appsv1.ControllerRevision{
+			ObjectMeta: metav1.ObjectMeta{
+				Name: fmt.Sprintf("test-revision-update-%d", i),
+			},
+			Data: runtime.RawExtension{Raw: []byte(`{}`)},
+		}, metav1.CreateOptions{})
+		if err != nil {
+			t.Errorf("expected nil create error, got: %v", err)
+			continue
+		}
+
+		updateError := new(http2.StreamError)
+		existing.Data = runtime.RawExtension{Raw: []byte(raw)}
+		if _, err := protoClient.AppsV1().ControllerRevisions(existing.Namespace).Update(context.TODO(), existing, metav1.UpdateOptions{}); errors.As(err, updateError) && updateError.Code == http2.ErrCodeInternal {
+			t.Logf("update returned internal error as expected with rawextension %#v: %v", raw, err)
+		} else {
+			t.Errorf("update returned unexpected error: %#v", err)
+		}
+	}
+}