Fix IllegalArgumentException when creating custom IndicesOption with empty Option or WildcardState set.

Original Pull Request #2076
Closes #2075

Author: pnowak85

Diff for: src/main/java/org/springframework/data/elasticsearch/core/RequestFactory.java

@@ -118,6 +118,7 @@
  * @author Farid Faoudi
  * @author Peer Mueller
  * @author Sijia Liu
+ * @author Peter Nowak
  * @since 4.0
  */
 class RequestFactory {
@@ -1248,7 +1249,11 @@ public org.elasticsearch.action.support.IndicesOptions toElasticsearchIndicesOpt
 				.map(it -> org.elasticsearch.action.support.IndicesOptions.WildcardStates.valueOf(it.name().toUpperCase()))
 				.collect(Collectors.toSet());
 
-		return new org.elasticsearch.action.support.IndicesOptions(EnumSet.copyOf(options), EnumSet.copyOf(wildcardStates));
+		return new org.elasticsearch.action.support.IndicesOptions(
+				options.isEmpty() ? EnumSet.noneOf(org.elasticsearch.action.support.IndicesOptions.Option.class)
+						: EnumSet.copyOf(options),
+				wildcardStates.isEmpty() ? EnumSet.noneOf(org.elasticsearch.action.support.IndicesOptions.WildcardStates.class)
+						: EnumSet.copyOf(wildcardStates));
 	}
 	// endregion
 

Diff for: src/test/java/org/springframework/data/elasticsearch/core/RequestFactoryTests.java

@@ -22,6 +22,7 @@
 import java.io.IOException;
 import java.time.Duration;
 import java.util.Arrays;
+import java.util.EnumSet;
 import java.util.HashSet;
 
 import org.elasticsearch.action.DocWriteRequest;
@@ -70,6 +71,7 @@
  * @author Peer Mueller
  * @author vdisk
  * @author Sijia Liu
+ * @author Peter Nowak
  */
 @SuppressWarnings("ConstantConditions")
 @ExtendWith(MockitoExtension.class)
@@ -628,6 +630,20 @@ void shouldAllowSourceQueryForReindexWithoutRemote() throws IOException, JSONExc
 		assertEquals(expected, json, false);
 	}
 
+	@Test // #2075
+	@DisplayName("should not fail on empty Option set during toElasticsearchIndicesOptions")
+	void shouldNotFailOnEmptyOptionsOnToElasticsearchIndicesOptions() {
+		assertThat(requestFactory.toElasticsearchIndicesOptions(new IndicesOptions(
+				EnumSet.noneOf(IndicesOptions.Option.class), EnumSet.of(IndicesOptions.WildcardStates.OPEN)))).isNotNull();
+	}
+
+	@Test // #2075
+	@DisplayName("should not fail on empty WildcardState set during toElasticsearchIndicesOptions")
+	void shouldNotFailOnEmptyWildcardStatesOnToElasticsearchIndicesOptions() {
+		assertThat(requestFactory.toElasticsearchIndicesOptions(IndicesOptions.STRICT_SINGLE_INDEX_NO_EXPAND_FORBID_CLOSED))
+				.isNotNull();
+	}
+
 	// region entities
 	static class Person {
 		@Nullable