DATAMONGO-1774 - Fix infinite loop in ReactiveMongoOperations#remove(Mono, String).

Original pull request: spring-projects#498.

Author: christophstrobl

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

@@ -1446,7 +1446,7 @@ public Mono<DeleteResult> remove(Mono<? extends Object> objectToRemove) {
 	 */
 	@Override
 	public Mono<DeleteResult> remove(Mono<? extends Object> objectToRemove, String collection) {
-		return objectToRemove.flatMap(o -> remove(objectToRemove, collection));
+		return objectToRemove.flatMap(it -> remove(it, collection));
 	}
 
 	/*

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

@@ -461,6 +461,52 @@ public void testFindAllAndRemoveFullyReturnsAndRemovesDocuments() {
 		StepVerifier.create(template.findOne(new Query(), Sample.class)).expectNext(data).verifyComplete();
 	}
 
+	@Test // DATAMONGO-1774
+	public void removeWithEmptyMonoShouldDoNothing() {
+
+		Sample spring = new Sample("100", "spring");
+		Sample data = new Sample("200", "data");
+		Sample mongodb = new Sample("300", "mongodb");
+
+		StepVerifier.create(template.insert(Arrays.asList(spring, data, mongodb), Sample.class)) //
+				.expectNextCount(3) //
+				.verifyComplete();
+
+		StepVerifier.create(template.remove(Mono.empty())).verifyComplete();
+		StepVerifier.create(template.count(new Query(), Sample.class)).expectNext(3L).verifyComplete();
+	}
+
+	@Test // DATAMONGO-1774
+	public void removeWithMonoShouldDeleteElement() {
+
+		Sample spring = new Sample("100", "spring");
+		Sample data = new Sample("200", "data");
+		Sample mongodb = new Sample("300", "mongodb");
+
+		StepVerifier.create(template.insert(Arrays.asList(spring, data, mongodb), Sample.class)) //
+				.expectNextCount(3) //
+				.verifyComplete();
+
+		StepVerifier.create(template.remove(Mono.just(spring))).expectNextCount(1).verifyComplete();
+		StepVerifier.create(template.count(new Query(), Sample.class)).expectNext(2L).verifyComplete();
+	}
+
+	@Test // DATAMONGO-1774
+	public void removeWithMonoAndCollectionShouldDeleteElement() {
+
+		Sample spring = new Sample("100", "spring");
+		Sample data = new Sample("200", "data");
+		Sample mongodb = new Sample("300", "mongodb");
+
+		StepVerifier.create(template.insert(Arrays.asList(spring, data, mongodb), Sample.class)) //
+				.expectNextCount(3) //
+				.verifyComplete();
+
+		StepVerifier.create(template.remove(Mono.just(spring), template.determineCollectionName(Sample.class)))
+				.expectNextCount(1).verifyComplete();
+		StepVerifier.create(template.count(new Query(), Sample.class)).expectNext(2L).verifyComplete();
+	}
+
 	@Test // DATAMONGO-1444
 	public void optimisticLockingHandling() {