HHH-15343 Fix NPE in type determination for case expression with null literal

hibernate-core/src/main/java/org/hibernate/query/internal/QueryHelper.java

@@ -56,8 +56,14 @@ public class QueryHelper {
 			return type2;
 		}
 
+		if ( type1.getExpressibleJavaType() == null ) {
+			return type2;
+		}
+		else if ( type2.getExpressibleJavaType() == null ) {
+			return type1;
+		}
 		// any other precedence rules?
-		if ( type2.getExpressibleJavaType().isWider( type1.getExpressibleJavaType() ) ) {
+		else if ( type2.getExpressibleJavaType().isWider( type1.getExpressibleJavaType() ) ) {
 			return type2;
 		}
 

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

@@ -0,0 +1,90 @@
+package org.hibernate.orm.test.query;
+
+import java.util.List;
+
+import org.hibernate.testing.TestForIssue;
+import org.hibernate.testing.orm.junit.DomainModel;
+import org.hibernate.testing.orm.junit.SessionFactory;
+import org.hibernate.testing.orm.junit.SessionFactoryScope;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import jakarta.persistence.Entity;
+import jakarta.persistence.Id;
+import jakarta.persistence.Table;
+
+import static org.hamcrest.CoreMatchers.is;
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.junit.jupiter.api.Assertions.assertNull;
+
+@DomainModel(
+		annotatedClasses = { SelectCaseWhenNullLiteralTest.Person.class }
+)
+@SessionFactory
+@TestForIssue(jiraKey = "HHH-15343")
+public class SelectCaseWhenNullLiteralTest {
+
+	@BeforeEach
+	public void setUp(SessionFactoryScope scope) {
+		scope.inTransaction(
+				session -> {
+					Person person = new Person( 1l, "Fab" );
+					session.persist( person );
+				}
+		);
+	}
+
+	@AfterEach
+	public void tearDown(SessionFactoryScope scope) {
+		scope.inTransaction(
+				session -> {
+					session.createQuery( "delete from Person" ).executeUpdate();
+				}
+		);
+	}
+
+	@Test
+	public void testSelectCaseWhenNullLiteral(SessionFactoryScope scope) {
+		scope.inTransaction(
+				session -> {
+					List result = session.createQuery( "select case when 1=1 then 1 else null end from Person p" ).list();
+					assertThat( result.size(), is( 1 ) );
+					assertThat( result.get( 0 ), is( 1 ) );
+				}
+		);
+	}
+
+	@Entity(name = "Person")
+	@Table(name = "PERSON_TABLE")
+	public static class Person {
+		@Id
+		private Long id;
+
+		private String name;
+
+		public Person() {
+		}
+
+		public Person(Long id, String name) {
+			this.id = id;
+			this.name = name;
+		}
+
+		public Long getId() {
+			return id;
+		}
+
+		public void setId(Long id) {
+			this.id = id;
+		}
+
+		public String getName() {
+			return name;
+		}
+
+		public void setName(String name) {
+			this.name = name;
+		}
+	}
+}