Do not override existing limit in R2dbcEntityTemplate.selectOne.

Closes #1233

Author: RobertHeim

spring-data-r2dbc/src/main/java/org/springframework/data/r2dbc/core/R2dbcEntityTemplate.java

@@ -87,6 +87,7 @@
  * @author Bogdan Ilchyshyn
  * @author Jens Schauder
  * @author Jose Luis Leon
+ * @author Robert Heim
  * @since 1.1
  */
 public class R2dbcEntityTemplate implements R2dbcEntityOperations, BeanFactoryAware, ApplicationContextAware {
@@ -420,7 +421,13 @@ private <T> RowsFetchSpec<T> doSelect(Query query, Class<?> entityClass, SqlIden
 	 */
 	@Override
 	public <T> Mono<T> selectOne(Query query, Class<T> entityClass) throws DataAccessException {
-		return doSelect(query.limit(2), entityClass, getTableName(entityClass), entityClass, RowsFetchSpec::one);
+		Query q = query;
+		/* If the query has not a defined limit, a limit of 2 is employed
+			to catch cases where the query would yield more than one result. */
+		if (query.getLimit() == -1) {
+			q = query.limit(2);
+		} // else: use the already defined limit.
+		return doSelect(q, entityClass, getTableName(entityClass), entityClass, RowsFetchSpec::one);
 	}
 
 	/*

spring-data-r2dbc/src/test/java/org/springframework/data/r2dbc/core/R2dbcEntityTemplateUnitTests.java

@@ -68,6 +68,7 @@
  *
  * @author Mark Paluch
  * @author Jose Luis Leon
+ * @author Robert Heim
  */
 public class R2dbcEntityTemplateUnitTests {
 
@@ -202,6 +203,22 @@ void shouldSelectOne() {
 		assertThat(statement.getBindings()).hasSize(1).containsEntry(0, Parameter.from("Walter"));
 	}
 
+	@Test // gh-220, gh-758
+	void shouldSelectOneDoNotOverrideExistingLimit() {
+
+		recorder.addStubbing(s -> s.startsWith("SELECT"), Collections.emptyList());
+
+		entityTemplate.selectOne(Query.query(Criteria.where("name").is("Walter")).sort(Sort.by("name")).limit(1), Person.class) //
+				.as(StepVerifier::create) //
+				.verifyComplete();
+
+		StatementRecorder.RecordedStatement statement = recorder.getCreatedStatement(s -> s.startsWith("SELECT"));
+
+		assertThat(statement.getSql())
+				.isEqualTo("SELECT person.* FROM person WHERE person.THE_NAME = $1 ORDER BY person.THE_NAME ASC LIMIT 1");
+		assertThat(statement.getBindings()).hasSize(1).containsEntry(0, Parameter.from("Walter"));
+	}
+
 	@Test // gh-220
 	void shouldUpdateByQuery() {