Kube real server-side apply with deletion...

main.go

package main

import (
	"context"
	"encoding/json"

	corev1 "k8s.io/api/core/v1"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/runtime"
	"k8s.io/apimachinery/pkg/types"
	ctrl "sigs.k8s.io/controller-runtime"
	"sigs.k8s.io/controller-runtime/pkg/client"
)

var scheme = runtime.NewScheme()

func main() {
	corev1.AddToScheme(scheme)

	err := run()
	if err != nil {
		panic(err)
	}
}

func run() error {
	restConfig := ctrl.GetConfigOrDie()
	c, err := client.New(restConfig, client.Options{})
	if err != nil {
		return err
	}

	ctx := context.Background()
	return update(ctx, c)
}

func create(ctx context.Context, c client.Client) error {
	cm := &corev1.ConfigMap{
		TypeMeta: metav1.TypeMeta{
			APIVersion: "v1",
			Kind:       "ConfigMap",
		},
		ObjectMeta: metav1.ObjectMeta{
			Name:      "test",
			Namespace: "default",
		},
		Data: map[string]string{
			"test": "test",
		},
	}
	patch, err := json.Marshal(cm)
	if err != nil {
		return err
	}
	if err := c.Patch(ctx, cm, client.RawPatch(types.ApplyPatchType, patch), client.FieldOwner("test")); err != nil {
		return err
	}
	return nil
}

func update(ctx context.Context, c client.Client) error {
	cm := &corev1.ConfigMap{
		TypeMeta: metav1.TypeMeta{
			APIVersion: "v1",
			Kind:       "ConfigMap",
		},
		ObjectMeta: metav1.ObjectMeta{
			Name:      "test",
			Namespace: "default",
		},
		Data: map[string]string{
			// "test": "test",
		},
	}
	patch, err := json.Marshal(cm)
	if err != nil {
		return err
	}
	if err := c.Patch(ctx, cm, client.RawPatch(types.ApplyPatchType, patch), client.FieldOwner("test")); err != nil {
		return err
	}
	return nil
}