HHH-16943 Add UniqueConstraintColumnOrderTest showing the column order issue

hibernate-core/src/test/java/org/hibernate/orm/test/schemaupdate/uniqueconstraint/UniqueConstraintColumnOrderTest.java

@@ -0,0 +1,79 @@
+/*
+ * Hibernate, Relational Persistence for Idiomatic Java
+ *
+ * License: GNU Lesser General Public License (LGPL), version 2.1 or later.
+ * See the lgpl.txt file in the root directory or <http://www.gnu.org/licenses/lgpl-2.1.html>.
+ */
+package org.hibernate.orm.test.schemaupdate.uniqueconstraint;
+
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.EnumSet;
+import java.util.List;
+import java.util.Map;
+
+import org.hibernate.boot.Metadata;
+import org.hibernate.cfg.AvailableSettings;
+import org.hibernate.jpa.boot.spi.Bootstrap;
+import org.hibernate.jpa.boot.spi.EntityManagerFactoryBuilder;
+import org.hibernate.jpa.boot.spi.PersistenceUnitDescriptor;
+import org.hibernate.tool.hbm2ddl.SchemaExport;
+import org.hibernate.tool.schema.TargetType;
+
+import org.hibernate.testing.orm.jpa.PersistenceUnitDescriptorAdapter;
+import org.hibernate.testing.orm.junit.JiraKey;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+
+import jakarta.persistence.Entity;
+import jakarta.persistence.EntityManagerFactory;
+import jakarta.persistence.Id;
+import jakarta.persistence.Table;
+import jakarta.persistence.UniqueConstraint;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+@JiraKey("HHH-16943")
+class UniqueConstraintColumnOrderTest {
+
+	@Test
+	public void testUniqueConstraintColumnOrder(@TempDir Path tempDir) throws Exception {
+		PersistenceUnitDescriptor puDescriptor = new PersistenceUnitDescriptorAdapter() {
+			@Override
+			public List<String> getManagedClassNames() {
+				return List.of( TestEntity.class.getName() );
+			}
+		};
+
+		Map<Object, Object> settings = Map.of( AvailableSettings.HBM2DDL_AUTO, "create" );
+		EntityManagerFactoryBuilder emfBuilder = Bootstrap.getEntityManagerFactoryBuilder( puDescriptor, settings );
+
+		Path ddlScript = tempDir.resolve( "ddl.sql" );
+
+		try (EntityManagerFactory entityManagerFactory = emfBuilder.build()) {
+			// we do not need the entityManagerFactory, but we need to build it in order to demonstrate the issue (HHH-16943)
+
+			Metadata metadata = emfBuilder.metadata();
+
+			new SchemaExport()
+					.setHaltOnError( true )
+					.setOutputFile( ddlScript.toString() )
+					.setFormat( true )
+					.create( EnumSet.of( TargetType.SCRIPT ), metadata );
+		}
+
+		String ddl = Files.readString( ddlScript );
+		assertThat( ddl ).contains( "constraint uk_b_a unique (b, a)" );
+	}
+
+	@Entity
+	@Table(uniqueConstraints = @UniqueConstraint(name = "uk_b_a", columnNames = { "b", "a" }))
+	static class TestEntity {
+
+		@Id
+		private Long id;
+		private String a;
+		private String b;
+
+	}
+}