DATAMONGO-2360 - Polishing.

Apply index hints in ReactiveMongoTemplate.count(…).

Original pull request: #788.

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

@@ -1275,6 +1275,9 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 			if (query.getSkip() > 0) {
 				options.skip((int) query.getSkip());
 			}
+			if (StringUtils.hasText(query.getHint())) {
+				options.hint(Document.parse(query.getHint()));
+			}
 
 			operations.forType(entityClass).getCollation(query).map(Collation::toMongoCollation) //
 					.ifPresent(options::collation);

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

@@ -407,6 +407,18 @@ public class ReactiveMongoTemplateUnitTests {
 		assertThat(options.getValue().getLimit()).isEqualTo(100);
 	}
 
+	@Test // DATAMONGO-2360
+	public void countShouldApplyQueryHintIfPresent() {
+
+		Document queryHint = new Document("age", 1);
+		template.count(new Query().withHint(queryHint), Person.class, "star-wars").subscribe();
+
+		ArgumentCaptor<CountOptions> options = ArgumentCaptor.forClass(CountOptions.class);
+		verify(collection).count(any(), options.capture());
+
+		assertThat(options.getValue().getHint()).isEqualTo(queryHint);
+	}
+
 	@Test // DATAMONGO-2215
 	public void updateShouldApplyArrayFilters() {