DATAJPA-974 - Query for tuples now uses joins correctly.

When creating the selections for a derived query using a projection we now explicitly create joins for plural attributes. Looks like Hibernate fails to create a proper query if the path is referred to via root.get(…) and the select clause includes references to other non-plural attributes.

src/main/java/org/springframework/data/jpa/repository/query/JpaQueryCreator.java

@@ -156,7 +156,9 @@ public class JpaQueryCreator extends AbstractQueryCreator<CriteriaQuery<? extend
 			List<Selection<?>> selections = new ArrayList<Selection<?>>();
 
 			for (String property : returnedType.getInputProperties()) {
-				selections.add(root.get(property).alias(property));
+
+				PropertyPath path = PropertyPath.from(property, returnedType.getDomainType());
+				selections.add(toExpressionRecursively(root, path).alias(property));
 			}
 
 			query = query.multiselect(selections);

src/test/java/org/springframework/data/jpa/repository/UserRepositoryFinderTests.java

@@ -226,4 +226,12 @@ public class UserRepositoryFinderTests {
 	public void translatesNotContainsToNotMemberOf() {
 		assertThat(userRepository.findByRolesNotContaining(drummer), hasItems(dave, oliver));
 	}
+
+	/**
+	 * @see DATAJPA-974
+	 */
+	@Test
+	public void executesQueryWithProjectionContainingReferenceToPluralAttribute() {
+		assertThat(userRepository.findRolesAndFirstnameBy(), is(notNullValue()));
+	}
 }

src/test/java/org/springframework/data/jpa/repository/sample/UserRepository.java

@@ -596,4 +596,13 @@ public interface UserRepository
 	 * @see DATAJPA-858
 	 */
 	List<User> findByRolesNameContaining(String name);
+
+	List<RolesAndFirstname> findRolesAndFirstnameBy();
+
+	static interface RolesAndFirstname {
+
+		String getFirstname();
+
+		Set<Role> getRoles();
+	}
 }