DATAMONGO-2374 - Fix simple type result handling for repository query methods.

Original pull request: #791.

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

@@ -66,8 +66,12 @@ class PropertyOperations {
 				projectionInformation.getInputProperties().forEach(it -> projectedFields.append(it.getName(), 1));
 			}
 		} else {
-			mappingContext.getRequiredPersistentEntity(targetType).doWithProperties(
-					(SimplePropertyHandler) persistentProperty -> projectedFields.append(persistentProperty.getName(), 1));
+
+			MongoPersistentEntity<?> entity = mappingContext.getPersistentEntity(targetType);
+			if(entity != null) {
+				entity.doWithProperties(
+						(SimplePropertyHandler) persistentProperty -> projectedFields.append(persistentProperty.getName(), 1));
+			}
 		}
 
 		return projectedFields;

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/repository/query/ReactiveMongoQueryExecution.java

@@ -174,6 +174,10 @@ interface ReactiveMongoQueryExecution {
 				return source;
 			}
 
+			if(!operations.getConverter().getMappingContext().hasPersistentEntityFor(returnedType.getReturnedType())) {
+				return source;
+			}
+
 			Converter<Object, Object> converter = new DtoInstantiatingConverter(returnedType.getReturnedType(),
 					operations.getConverter().getMappingContext(), instantiators);
 

spring-data-mongodb/src/test/java/org/springframework/data/mongodb/repository/AbstractPersonRepositoryIntegrationTests.java

@@ -1302,4 +1302,11 @@ public abstract class AbstractPersonRepositoryIntegrationTests {
 		// assertThat(target).isNotNull();
 		// assertThat(target.getShippingAddresses()).hasSize(1);
 	}
+
+	@Test // DATAMONGO-2374
+	public void findsWithNativeProjection() {
+
+		assertThat(repository.findDocumentById(dave.getId()).get()).containsEntry("firstname", dave.getFirstname())
+				.containsEntry("lastname", dave.getLastname());
+	}
 }

spring-data-mongodb/src/test/java/org/springframework/data/mongodb/repository/PersonRepository.java

@@ -362,4 +362,7 @@ public interface PersonRepository extends MongoRepository<Person, String>, Query
 
 	@Query(value = "{ 'shippingAddresses' : { '$elemMatch' : { 'city' : { '$eq' : 'lnz' } } } }", fields = "{ 'shippingAddresses.$': ?0 }")
 	Person findWithArrayPositionInProjection(int position);
+
+	@Query(value="{_id:?0}")
+	Optional<org.bson.Document> findDocumentById(String id);
 }

spring-data-mongodb/src/test/java/org/springframework/data/mongodb/repository/ReactiveMongoRepositoryTests.java

@@ -384,6 +384,16 @@ public class ReactiveMongoRepositoryTests implements BeanClassLoaderAware, BeanF
 				.verifyComplete();
 	}
 
+	@Test // DATAMONGO-2374
+	public void findsWithNativeProjection() {
+
+		repository.findDocumentById(dave.getId()) //
+				.as(StepVerifier::create) //
+				.consumeNextWith(it -> {
+					assertThat(it).containsEntry("firstname", dave.getFirstname()).containsEntry("lastname", dave.getLastname());
+				}).verifyComplete();
+	}
+
 	interface ReactivePersonRepository extends ReactiveMongoRepository<Person, String> {
 
 		Flux<Person> findByLastname(String lastname);
@@ -422,6 +432,9 @@ public class ReactiveMongoRepositoryTests implements BeanClassLoaderAware, BeanF
 
 		@Query(sort = "{ age : -1 }")
 		Flux<Person> findByAgeGreaterThan(int age, Sort sort);
+
+		@Query(value = "{_id:?0}")
+		Mono<org.bson.Document> findDocumentById(String id);
 	}
 
 	interface ReactiveContactRepository extends ReactiveMongoRepository<Contact, String> {}