Fix index out of range panic for kubectl alpha debug

Fix containerNameToRef func to get init containers and ephemeral containers properly.

Set EphemeralContainers in generatePodCopyWithDebugContainer func to nil which means
dropping ephemeral containers from a copy of pod so that it can be created successfully,
otherwise it is rejected by the API server.

Author: kiyoshim55

staging/src/k8s.io/kubectl/pkg/cmd/debug/debug.go

@@ -485,6 +485,8 @@ func (o *DebugOptions) generatePodCopyWithDebugContainer(pod *corev1.Pod) (*core
 		},
 		Spec: *pod.Spec.DeepCopy(),
 	}
+	// set EphemeralContainers to nil so that the copy of pod can be created
+	copied.Spec.EphemeralContainers = nil
 	// change ShareProcessNamespace configuration only when commanded explicitly
 	if o.shareProcessedChanged {
 		copied.Spec.ShareProcessNamespace = pointer.BoolPtr(o.ShareProcesses)
@@ -544,11 +546,11 @@ func containerNameToRef(pod *corev1.Pod) map[string]*corev1.Container {
 		names[ref.Name] = ref
 	}
 	for i := range pod.Spec.InitContainers {
-		ref := &pod.Spec.Containers[i]
+		ref := &pod.Spec.InitContainers[i]
 		names[ref.Name] = ref
 	}
 	for i := range pod.Spec.EphemeralContainers {
-		ref := &pod.Spec.Containers[i]
+		ref := (*corev1.Container)(&pod.Spec.EphemeralContainers[i].EphemeralContainerCommon)
 		names[ref.Name] = ref
 	}
 	return names

staging/src/k8s.io/kubectl/pkg/cmd/debug/debug_test.go

@@ -153,6 +153,74 @@ func TestGenerateDebugContainer(t *testing.T) {
 				},
 			},
 		},
+		{
+			name: "pod with init containers",
+			opts: &DebugOptions{
+				Image:      "busybox",
+				PullPolicy: corev1.PullIfNotPresent,
+			},
+			pod: &corev1.Pod{
+				Spec: corev1.PodSpec{
+					InitContainers: []corev1.Container{
+						{
+							Name: "init-container-1",
+						},
+						{
+							Name: "init-container-2",
+						},
+					},
+					Containers: []corev1.Container{
+						{
+							Name: "debugger",
+						},
+					},
+				},
+			},
+			expected: &corev1.EphemeralContainer{
+				EphemeralContainerCommon: corev1.EphemeralContainerCommon{
+					Name:                     "debugger-1",
+					Image:                    "busybox",
+					ImagePullPolicy:          "IfNotPresent",
+					TerminationMessagePolicy: "File",
+				},
+			},
+		},
+		{
+			name: "pod with ephemeral containers",
+			opts: &DebugOptions{
+				Image:      "busybox",
+				PullPolicy: corev1.PullIfNotPresent,
+			},
+			pod: &corev1.Pod{
+				Spec: corev1.PodSpec{
+					Containers: []corev1.Container{
+						{
+							Name: "debugger",
+						},
+					},
+					EphemeralContainers: []corev1.EphemeralContainer{
+						{
+							EphemeralContainerCommon: corev1.EphemeralContainerCommon{
+								Name: "ephemeral-container-1",
+							},
+						},
+						{
+							EphemeralContainerCommon: corev1.EphemeralContainerCommon{
+								Name: "ephemeral-container-2",
+							},
+						},
+					},
+				},
+			},
+			expected: &corev1.EphemeralContainer{
+				EphemeralContainerCommon: corev1.EphemeralContainerCommon{
+					Name:                     "debugger-1",
+					Image:                    "busybox",
+					ImagePullPolicy:          "IfNotPresent",
+					TerminationMessagePolicy: "File",
+				},
+			},
+		},
 	} {
 		t.Run(tc.name, func(t *testing.T) {
 			tc.opts.IOStreams = genericclioptions.NewTestIOStreamsDiscard()
@@ -590,6 +658,110 @@ func TestGeneratePodCopyWithDebugContainer(t *testing.T) {
 				},
 			},
 		},
+		{
+			name: "pod with init containers",
+			opts: &DebugOptions{
+				CopyTo:     "debugger",
+				Image:      "busybox",
+				PullPolicy: corev1.PullIfNotPresent,
+			},
+			pod: &corev1.Pod{
+				ObjectMeta: metav1.ObjectMeta{
+					Name: "target",
+				},
+				Spec: corev1.PodSpec{
+					InitContainers: []corev1.Container{
+						{
+							Name: "init-container-1",
+						},
+						{
+							Name: "init-container-2",
+						},
+					},
+					Containers: []corev1.Container{
+						{
+							Name: "debugger-1",
+						},
+					},
+				},
+			},
+			expected: &corev1.Pod{
+				ObjectMeta: metav1.ObjectMeta{
+					Name: "debugger",
+				},
+				Spec: corev1.PodSpec{
+					InitContainers: []corev1.Container{
+						{
+							Name: "init-container-1",
+						},
+						{
+							Name: "init-container-2",
+						},
+					},
+					Containers: []corev1.Container{
+						{
+							Name: "debugger-1",
+						},
+						{
+							Name:                     "debugger-2",
+							Image:                    "busybox",
+							ImagePullPolicy:          corev1.PullIfNotPresent,
+							TerminationMessagePolicy: corev1.TerminationMessageReadFile,
+						},
+					},
+				},
+			},
+		},
+		{
+			name: "pod with ephemeral containers",
+			opts: &DebugOptions{
+				CopyTo:     "debugger",
+				Image:      "busybox",
+				PullPolicy: corev1.PullIfNotPresent,
+			},
+			pod: &corev1.Pod{
+				ObjectMeta: metav1.ObjectMeta{
+					Name: "target",
+				},
+				Spec: corev1.PodSpec{
+					Containers: []corev1.Container{
+						{
+							Name: "debugger-1",
+						},
+					},
+					EphemeralContainers: []corev1.EphemeralContainer{
+						{
+							EphemeralContainerCommon: corev1.EphemeralContainerCommon{
+								Name: "ephemeral-container-1",
+							},
+						},
+						{
+							EphemeralContainerCommon: corev1.EphemeralContainerCommon{
+								Name: "ephemeral-container-2",
+							},
+						},
+					},
+				},
+			},
+			expected: &corev1.Pod{
+				ObjectMeta: metav1.ObjectMeta{
+					Name: "debugger",
+				},
+				Spec: corev1.PodSpec{
+					Containers: []corev1.Container{
+						{
+							Name: "debugger-1",
+						},
+						{
+							Name:                     "debugger-2",
+							Image:                    "busybox",
+							ImagePullPolicy:          corev1.PullIfNotPresent,
+							TerminationMessagePolicy: corev1.TerminationMessageReadFile,
+						},
+					},
+				},
+			},
+		},
 		{
 			name: "shared process namespace",
 			opts: &DebugOptions{