fix: omit nil/empty containers from ExtraPodSpec JSON to prevent CRD validation failure (#6255)

Signed-off-by: Julien Mancuso <jmancuso@nvidia.com>

deploy/operator/api/v1alpha1/common.go

@@ -18,6 +18,8 @@
 package v1alpha1
 
 import (
+	"encoding/json"
+
 	autoscalingv2 "k8s.io/api/autoscaling/v2"
 	corev1 "k8s.io/api/core/v1"
 	"k8s.io/apimachinery/pkg/api/resource"
@@ -124,6 +126,34 @@ type ExtraPodSpec struct {
 	MainContainer   *corev1.Container `json:"mainContainer,omitempty"`
 }
 
+// MarshalJSON implements json.Marshaler for ExtraPodSpec.
+//
+// corev1.PodSpec.Containers is declared without omitempty, so a nil slice
+// serializes as "containers": null.  The CRD structural schema defines
+// containers as type: array and rejects null.  This custom marshaller shadows
+// the Containers field with an omitempty-tagged copy so that nil/empty
+// Containers are omitted from the JSON output entirely.
+func (e ExtraPodSpec) MarshalJSON() ([]byte, error) {
+	// Type alias strips methods from corev1.PodSpec, preventing infinite
+	// recursion through any MarshalJSON defined on PodSpec.
+	type PodSpecAlias corev1.PodSpec
+
+	aux := struct {
+		*PodSpecAlias `json:",inline"`
+		Containers    []corev1.Container `json:"containers,omitempty"`
+		MainContainer *corev1.Container  `json:"mainContainer,omitempty"`
+	}{}
+
+	if e.PodSpec != nil {
+		a := PodSpecAlias(*e.PodSpec)
+		aux.PodSpecAlias = &a
+		aux.Containers = e.PodSpec.Containers
+	}
+	aux.MainContainer = e.MainContainer
+
+	return json.Marshal(aux)
+}
+
 // ScalingAdapter configures whether a service uses the DynamoGraphDeploymentScalingAdapter
 // for replica management. When enabled, the DGDSA owns the replicas field and
 // external autoscalers (HPA, KEDA, Planner) can control scaling via the Scale subresource.

deploy/operator/api/v1alpha1/common_test.go

+/*
+ * SPDX-FileCopyrightText: Copyright (c) 2025-2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * 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 v1alpha1
+
+import (
+	"encoding/json"
+	"reflect"
+	"testing"
+
+	corev1 "k8s.io/api/core/v1"
+)
+
+func TestExtraPodSpec_MarshalJSON(t *testing.T) {
+	tests := []struct {
+		name     string
+		spec     ExtraPodSpec
+		wantJSON string
+	}{
+		{
+			name: "nil PodSpec with mainContainer",
+			spec: ExtraPodSpec{
+				PodSpec:       nil,
+				MainContainer: &corev1.Container{Name: "main"},
+			},
+			wantJSON: `{"mainContainer":{"name":"main","resources":{}}}`,
+		},
+		{
+			name: "nil Containers omits containers key entirely",
+			spec: ExtraPodSpec{
+				PodSpec: &corev1.PodSpec{
+					NodeSelector: map[string]string{"gpu": "true"},
+				},
+			},
+			wantJSON: `{"nodeSelector":{"gpu":"true"}}`,
+		},
+		{
+			name: "empty Containers omits containers key",
+			spec: ExtraPodSpec{
+				PodSpec: &corev1.PodSpec{
+					Containers: []corev1.Container{},
+				},
+			},
+			wantJSON: `{}`,
+		},
+		{
+			name: "populated Containers are serialized",
+			spec: ExtraPodSpec{
+				PodSpec: &corev1.PodSpec{
+					Containers: []corev1.Container{{Name: "sidecar"}},
+				},
+			},
+			wantJSON: `{"containers":[{"name":"sidecar","resources":{}}]}`,
+		},
+		{
+			name: "tolerations preserved without containers",
+			spec: ExtraPodSpec{
+				PodSpec: &corev1.PodSpec{
+					Tolerations: []corev1.Toleration{{Key: "nvidia.com/gpu"}},
+				},
+			},
+			wantJSON: `{"tolerations":[{"key":"nvidia.com/gpu"}]}`,
+		},
+		{
+			name: "mainContainer alongside PodSpec fields",
+			spec: ExtraPodSpec{
+				PodSpec: &corev1.PodSpec{
+					NodeSelector: map[string]string{"zone": "us-east"},
+				},
+				MainContainer: &corev1.Container{Name: "main"},
+			},
+			wantJSON: `{"nodeSelector":{"zone":"us-east"},"mainContainer":{"name":"main","resources":{}}}`,
+		},
+		{
+			name:     "nil PodSpec and nil mainContainer",
+			spec:     ExtraPodSpec{},
+			wantJSON: `{}`,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := json.Marshal(tt.spec)
+			if err != nil {
+				t.Fatalf("MarshalJSON() error = %v", err)
+			}
+
+			if string(got) != tt.wantJSON {
+				t.Errorf("MarshalJSON() mismatch\n got: %s\nwant: %s", string(got), tt.wantJSON)
+			}
+		})
+	}
+}
+
+func TestExtraPodSpec_MarshalJSON_RoundTrip(t *testing.T) {
+	original := ExtraPodSpec{
+		PodSpec: &corev1.PodSpec{
+			Containers:   []corev1.Container{{Name: "main", Image: "nginx"}},
+			NodeSelector: map[string]string{"gpu": "true"},
+			Tolerations:  []corev1.Toleration{{Key: "nvidia.com/gpu", Operator: corev1.TolerationOpExists}},
+		},
+		MainContainer: &corev1.Container{Name: "override", Image: "custom"},
+	}
+
+	data, err := json.Marshal(original)
+	if err != nil {
+		t.Fatalf("MarshalJSON() error = %v", err)
+	}
+
+	var restored ExtraPodSpec
+	if err := json.Unmarshal(data, &restored); err != nil {
+		t.Fatalf("UnmarshalJSON() error = %v", err)
+	}
+
+	if !reflect.DeepEqual(original.PodSpec, restored.PodSpec) {
+		t.Errorf("round-trip: PodSpec mismatch\n got: %+v\nwant: %+v", restored.PodSpec, original.PodSpec)
+	}
+
+	if !reflect.DeepEqual(original.MainContainer, restored.MainContainer) {
+		t.Errorf("round-trip: MainContainer mismatch\n got: %+v\nwant: %+v", restored.MainContainer, original.MainContainer)
+	}
+}