DATAMONGO-2360 - Apply query hint to count queries.

Original pull request: #788.

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

@@ -1172,6 +1172,9 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 		if (query.getSkip() > 0) {
 			options.skip((int) query.getSkip());
 		}
+		if (StringUtils.hasText(query.getHint())) {
+			options.hint(Document.parse(query.getHint()));
+		}
 
 		Document document = queryMapper.getMappedObject(query.getQueryObject(),
 				Optional.ofNullable(entityClass).map(it -> mappingContext.getPersistentEntity(entityClass)));

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

@@ -932,6 +932,18 @@ public class MongoTemplateUnitTests extends MongoOperationsUnitTests {
 				.isEqualTo(com.mongodb.client.model.Collation.builder().locale("fr").build());
 	}
 
+	@Test // DATAMONGO-2360
+	public void countShouldApplyQueryHintIfPresent() {
+
+		Document queryHint = new Document("age", 1);
+		template.count(new BasicQuery("{}").withHint(queryHint), AutogenerateableId.class);
+
+		ArgumentCaptor<CountOptions> options = ArgumentCaptor.forClass(CountOptions.class);
+		verify(collection).count(any(), options.capture());
+
+		assertThat(options.getValue().getHint()).isEqualTo(queryHint);
+	}
+
 	@Test // DATAMONGO-1733
 	public void appliesFieldsWhenInterfaceProjectionIsClosedAndQueryDoesNotDefineFields() {