add unit test and documentation for finalizers (#2509)

* add unit test and documentation for finalizers
* error msg with lower case and cover sync case
* try to avoid adding json-patch dependency
* use Update to remove finalizer
* changing status and finalizer during create
* do not call Delete() twice

pkg/util/k8sutil/k8sutil.go

@@ -213,6 +213,37 @@ func (client *KubernetesClient) SetPostgresCRDStatus(clusterName spec.Namespaced
 	return pg, nil
 }
 
+// SetFinalizer of Postgres cluster
+func (client *KubernetesClient) SetFinalizer(clusterName spec.NamespacedName, pg *apiacidv1.Postgresql, finalizers []string) (*apiacidv1.Postgresql, error) {
+	var (
+		updatedPg *apiacidv1.Postgresql
+		patch     []byte
+		err       error
+	)
+	pg.ObjectMeta.SetFinalizers(finalizers)
+
+	if len(finalizers) > 0 {
+		patch, err = json.Marshal(struct {
+			PgMetadata interface{} `json:"metadata"`
+		}{&pg.ObjectMeta})
+		if err != nil {
+			return pg, fmt.Errorf("could not marshal ObjectMeta: %v", err)
+		}
+
+		updatedPg, err = client.PostgresqlsGetter.Postgresqls(clusterName.Namespace).Patch(
+			context.TODO(), clusterName.Name, types.MergePatchType, patch, metav1.PatchOptions{})
+	} else {
+		// in case finalizers are empty and update is needed to remove
+		updatedPg, err = client.PostgresqlsGetter.Postgresqls(clusterName.Namespace).Update(
+			context.TODO(), pg, metav1.UpdateOptions{})
+	}
+	if err != nil {
+		return updatedPg, fmt.Errorf("could not set finalizer: %v", err)
+	}
+
+	return updatedPg, nil
+}
+
 // SamePDB compares the PodDisruptionBudgets
 func SamePDB(cur, new *apipolicyv1.PodDisruptionBudget) (match bool, reason string) {
 	//TODO: improve comparison

pkg/util/util.go

@@ -152,6 +152,17 @@ func IsEqualIgnoreOrder(a, b []string) bool {
 	return reflect.DeepEqual(a_copy, b_copy)
 }
 
+// Iterate through slice and remove certain string, then return cleaned slice
+func RemoveString(slice []string, s string) (result []string) {
+	for _, item := range slice {
+		if item == s {
+			continue
+		}
+		result = append(result, item)
+	}
+	return result
+}
+
 // SliceReplaceElement
 func StringSliceReplaceElement(s []string, a, b string) (result []string) {
 	tmp := make([]string, 0, len(s))

pkg/util/util_test.go

@@ -66,6 +66,17 @@ var substractTest = []struct {
 	{[]string{"a"}, []string{""}, []string{"a"}, false},
 }
 
+var removeStringTest = []struct {
+	slice  []string
+	item   string
+	result []string
+}{
+	{[]string{"a", "b", "c"}, "b", []string{"a", "c"}},
+	{[]string{"a"}, "b", []string{"a"}},
+	{[]string{"a"}, "a", []string{}},
+	{[]string{}, "a", []string{}},
+}
+
 var sliceContaintsTest = []struct {
 	slice []string
 	item  string
@@ -200,6 +211,15 @@ func TestFindNamedStringSubmatch(t *testing.T) {
 	}
 }
 
+func TestRemoveString(t *testing.T) {
+	for _, tt := range removeStringTest {
+		res := RemoveString(tt.slice, tt.item)
+		if !IsEqualIgnoreOrder(res, tt.result) {
+			t.Errorf("RemoveString expected: %#v, got: %#v", tt.result, res)
+		}
+	}
+}
+
 func TestSliceContains(t *testing.T) {
 	for _, tt := range sliceContaintsTest {
 		res := SliceContains(tt.slice, tt.item)