DATAMONGO-2219 - Fix ReactiveMongoTemplate.findAllAndRemove(…) if the query yields no results.

ReactiveMongoTemplate.findAllAndRemove(…) now completes successfully without emitting a result if the find query yields no hits. We no longer call the subsequent remove query if without previous results.

Original Pull Request: #657

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

@@ -41,6 +41,7 @@ import org.reactivestreams.Publisher;
 import org.reactivestreams.Subscriber;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
+
 import org.springframework.beans.BeansException;
 import org.springframework.context.ApplicationContext;
 import org.springframework.context.ApplicationContextAware;
@@ -2144,7 +2145,7 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 
 		Flux<T> flux = find(query, entityClass, collectionName);
 
-		return Flux.from(flux).collectList()
+		return Flux.from(flux).collectList().filter(it -> !it.isEmpty())
 				.flatMapMany(list -> Flux.from(remove(operations.getByIdInQuery(list), entityClass, collectionName))
 						.flatMap(deleteResult -> Flux.fromIterable(list)));
 	}

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

@@ -54,6 +54,7 @@ import org.junit.Rule;
 import org.junit.Test;
 import org.junit.rules.ExpectedException;
 import org.junit.runner.RunWith;
+
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.context.ConfigurableApplicationContext;
 import org.springframework.dao.DataIntegrityViolationException;
@@ -634,6 +635,15 @@ public class ReactiveMongoTemplateTests {
 		StepVerifier.create(template.findOne(new Query(), Sample.class)).expectNext(data).verifyComplete();
 	}
 
+	@Test // DATAMONGO-2219
+	public void testFindAllAndRemoveReturnsEmptyWithoutMatches() {
+
+		Query qry = query(where("field").in("spring", "mongodb"));
+		template.findAllAndRemove(qry, Sample.class).as(StepVerifier::create).verifyComplete();
+
+		template.count(new Query(), Sample.class).as(StepVerifier::create).expectNext(0L).verifyComplete();
+	}
+
 	@Test // DATAMONGO-1774
 	public void testFindAllAndRemoveByCollectionReturnsAndRemovesDocuments() {