Fix IndexOptions.expireAfter setting wrong property.

Resolves: #4851

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/index/IndexOptions.java

@@ -86,13 +86,14 @@ public static IndexOptions hidden() {
 	public static IndexOptions expireAfter(Duration duration) {
 
 		IndexOptions options = new IndexOptions();
-		options.unique = Unique.YES;
+		options.expire = duration;
 		return options;
 	}
 
 	/**
 	 * @return the expiration time. A {@link Duration#isNegative() negative value} represents no expiration, {@literal null} if not set.
 	 */
+	@Nullable
 	public Duration getExpire() {
 		return expire;
 	}
@@ -151,7 +152,6 @@ public Document toDocument() {
 			document.put("hidden", hidden);
 		}
 
-
 		if (expire != null && !expire.isNegative()) {
 			document.put("expireAfterSeconds", expire.getSeconds());
 		}

spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/index/IndexOptionsUnitTests.java

@@ -0,0 +1,82 @@
+/*
+ * Copyright 2024 the original author or authors.
+ *
+ * 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
+ *
+ *      https://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 org.springframework.data.mongodb.core.index;
+
+import static org.springframework.data.mongodb.test.util.Assertions.assertThat;
+
+import java.time.Duration;
+
+import org.bson.Document;
+import org.junit.jupiter.api.Test;
+import org.springframework.data.mongodb.core.index.IndexOptions.Unique;
+
+/**
+ * @author Christoph Strobl
+ */
+class IndexOptionsUnitTests {
+
+	@Test // GH-4851
+	void noneIsEmpty() {
+
+		IndexOptions options = IndexOptions.none();
+
+		assertThat(options.getExpire()).isNull();
+		assertThat(options.getUnique()).isNull();
+		assertThat(options.isHidden()).isNull();
+		assertThat(options.toDocument()).isEqualTo(new Document());
+	}
+
+	@Test // GH-4851
+	void uniqueSetsFlag() {
+
+		IndexOptions options = IndexOptions.unique();
+
+		assertThat(options.getUnique()).isEqualTo(Unique.YES);
+		assertThat(options.toDocument()).containsEntry("unique", true);
+
+		options.setUnique(Unique.NO);
+		assertThat(options.toDocument()).containsEntry("unique", false);
+
+		options.setUnique(Unique.PREPARE);
+		assertThat(options.toDocument()).containsEntry("prepareUnique", true);
+	}
+
+	@Test // GH-4851
+	void hiddenSetsFlag() {
+
+		IndexOptions options = IndexOptions.hidden();
+
+		assertThat(options.isHidden()).isTrue();
+		assertThat(options.toDocument()).containsEntry("hidden", true);
+	}
+
+	@Test // GH-4851
+	void expireAfterSetsExpiration() {
+
+		Duration duration = Duration.ofMinutes(2);
+		IndexOptions options = IndexOptions.expireAfter(duration);
+
+		assertThat(options.getExpire()).isEqualTo(duration);
+		assertThat(options.toDocument()).containsEntry("expireAfterSeconds", duration.toSeconds());
+	}
+
+	@Test // GH-4851
+	void expireAfterForZeroAndNegativeDuration() {
+
+		assertThat(IndexOptions.expireAfter(Duration.ZERO).toDocument()).containsEntry("expireAfterSeconds", 0L);
+		assertThat(IndexOptions.expireAfter(Duration.ofSeconds(-1)).toDocument()).isEmpty();
+	}
+}