HHH-15390 Add test for issue

hibernate-core/src/test/java/org/hibernate/orm/test/query/ToHqlStringTest.java

@@ -0,0 +1,77 @@
+package org.hibernate.orm.test.query;
+
+import org.hibernate.query.spi.SqmQuery;
+
+import org.hibernate.testing.TestForIssue;
+import org.hibernate.testing.orm.junit.EntityManagerFactoryScope;
+import org.hibernate.testing.orm.junit.Jpa;
+import org.junit.jupiter.api.Test;
+
+import jakarta.persistence.Entity;
+import jakarta.persistence.Id;
+import jakarta.persistence.Query;
+import jakarta.persistence.TypedQuery;
+import jakarta.persistence.criteria.CriteriaBuilder;
+import jakarta.persistence.criteria.CriteriaQuery;
+import jakarta.persistence.criteria.Expression;
+import jakarta.persistence.criteria.Root;
+
+@Jpa(
+		annotatedClasses = ToHqlStringTest.TestEntity.class
+)
+@TestForIssue( jiraKey = "HHH-15389")
+public class ToHqlStringTest {
+
+	@Test
+	public void testCriteriaCountDistinctToHqlString(EntityManagerFactoryScope scope) {
+		scope.inTransaction(
+				entityManager -> {
+					CriteriaBuilder builder = entityManager.getCriteriaBuilder();
+					CriteriaQuery<Long> criteriaQuery = builder.createQuery( Long.class );
+
+					Root<TestEntity> root = criteriaQuery.from( TestEntity.class );
+					Expression<Long> countDistinct = builder.countDistinct( root );
+					criteriaQuery = criteriaQuery.select( countDistinct );
+
+					TypedQuery<Long> query = entityManager.createQuery( criteriaQuery );
+					( (SqmQuery) query ).getSqmStatement().toHqlString();
+				}
+		);
+	}
+
+	@Test
+	public void testHqlCountDistinctToHqlString(EntityManagerFactoryScope scope) {
+		scope.inTransaction(
+				entityManager -> {
+					Query query = entityManager.createQuery( "select count (distinct t) from TestEntity t" );
+					( (SqmQuery) query ).getSqmStatement().toHqlString();
+				}
+		);
+	}
+
+	@Test
+	public void testDynamicInstantiationToHqlString(EntityManagerFactoryScope scope){
+		scope.inTransaction(
+				entityManager -> {
+					Query query = entityManager.createQuery( "select new org.hibernate.orm.test.query.ToHqlStringTest$TestDto("
+					+ " t.id, t.name ) from TestEntity t" );
+					( (SqmQuery) query ).getSqmStatement().toHqlString();
+				}
+		);
+	}
+
+	public static class TestDto {
+		@Id
+		public Integer id;
+
+		public String name;
+	}
+
+	@Entity(name = "TestEntity")
+	public static class TestEntity {
+		@Id
+		public Integer id;
+
+		public String name;
+	}
+}