Align @Indexed(expireAfter) with expireAfterSeconds.

This commit fixes an issue where expireAfter=0s behaves differently from expireAfterSeconds=0 where the former would not be applied.

Closes #4844
Original pull request: #4848

Author: christophstrobl

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

@@ -564,7 +564,7 @@ protected IndexDefinitionHolder createIndexDefinition(String dotPath, String col
 
 			Duration timeout = computeIndexTimeout(index.expireAfter(),
 					() -> getEvaluationContextForProperty(persistentProperty.getOwner()));
-			if (!timeout.isZero() && !timeout.isNegative()) {
+			if (!timeout.isNegative()) {
 				indexDefinition.expire(timeout);
 			}
 		}

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

@@ -222,6 +222,15 @@ public void shouldResolveTimeoutFromString() {
 			assertThat(indexDefinitions.get(0).getIndexOptions()).containsEntry("expireAfterSeconds", 600L);
 		}
 
+		@Test // GH-4844
+		public void shouldResolveZeroTimeoutFromString() {
+
+			List<IndexDefinitionHolder> indexDefinitions = prepareMappingContextAndResolveIndexForType(
+				WithExpireAfterZeroSecondsAsPlainString.class);
+
+			assertThat(indexDefinitions.get(0).getIndexOptions()).containsEntry("expireAfterSeconds", 0L);
+		}
+
 		@Test // DATAMONGO-2112
 		public void shouldResolveTimeoutFromIso8601String() {
 
@@ -383,6 +392,11 @@ class WithExpireAfterAsPlainString {
 			@Indexed(expireAfter = "10m") String withTimeout;
 		}
 
+		@Document
+		class WithExpireAfterZeroSecondsAsPlainString {
+			@Indexed(expireAfter = "0s") String withTimeout;
+		}
+
 		@Document
 		class WithIso8601Style {
 			@Indexed(expireAfter = "P1D") String withTimeout;