Reproducer

Author: yrodiere

orm/hibernate-orm-6/src/test/java/org/hibernate/bugs/MyEntity.java

@@ -0,0 +1,31 @@
+package org.hibernate.bugs;
+
+import jakarta.persistence.EmbeddedId;
+import jakarta.persistence.Entity;
+
+@Entity
+public class MyEntity {
+
+	// The name of this property must be (alphabetically) before the name of "data" to trigger the bug.
+	// Yes, it's weird.
+	@EmbeddedId
+	private MyEntityId anId;
+
+	private String data;
+
+	public MyEntityId getAnId() {
+		return anId;
+	}
+
+	public void setAnId(MyEntityId anId) {
+		this.anId = anId;
+	}
+
+	public String getData() {
+		return data;
+	}
+
+	public void setData(String data) {
+		this.data = data;
+	}
+}

orm/hibernate-orm-6/src/test/java/org/hibernate/bugs/MyEntityId.java

@@ -0,0 +1,39 @@
+package org.hibernate.bugs;
+
+import java.util.Objects;
+
+import jakarta.persistence.Embeddable;
+
+@Embeddable
+public class MyEntityId {
+	private long val;
+
+	protected MyEntityId() {
+	}
+
+	public MyEntityId(long val) {
+		this.val = val;
+	}
+
+	public long getVal() {
+		return val;
+	}
+
+	public void setVal(long val) {
+		this.val = val;
+	}
+
+	@Override
+	public boolean equals(Object o) {
+		if ( o == null || getClass() != o.getClass() ) {
+			return false;
+		}
+		MyEntityId id = (MyEntityId) o;
+		return val == id.val;
+	}
+
+	@Override
+	public int hashCode() {
+		return Objects.hashCode( val );
+	}
+}

orm/hibernate-orm-6/src/test/java/org/hibernate/bugs/QuarkusLikeORMUnitTestCase.java

@@ -15,6 +15,8 @@
  */
 package org.hibernate.bugs;
 
+import static org.assertj.core.api.Assertions.assertThat;
+
 import org.hibernate.cfg.AvailableSettings;
 
 import org.hibernate.testing.bytecode.enhancement.CustomEnhancementContext;
@@ -34,9 +36,7 @@
  */
 @DomainModel(
 		annotatedClasses = {
-				// Add your entities here, e.g.:
-				// Foo.class,
-				// Bar.class
+				MyEntity.class
 		}
 )
 @ServiceRegistry(
@@ -67,9 +67,24 @@ class QuarkusLikeORMUnitTestCase {
 
 	// Add your tests, using standard JUnit.
 	@Test
-	void hhh123Test(SessionFactoryScope scope) throws Exception {
+	void hhh123Test(SessionFactoryScope scope) {
+		var entity = new MyEntity();
+		entity.setAnId( new MyEntityId( 1L ) );
+		entity.setData( "initial" );
+		var entityAfterFirstMerge = scope.fromTransaction( session -> {
+			return session.merge( entity );
+		} );
+
+		// This is unnecessary, but should be harmless... Unfortunately it causes dirty checking to misbehave.
+		entityAfterFirstMerge.setAnId( new MyEntityId( 1L ) );
+
+		scope.inTransaction( session -> {
+			entityAfterFirstMerge.setData( "updated" );
+			session.merge( entityAfterFirstMerge );
+		} );
 		scope.inTransaction( session -> {
-			// Do stuff...
+			var entityFromDb = session.find( MyEntity.class, new MyEntityId( 1L ) );
+			assertThat( entityFromDb.getData() ).isEqualTo( "updated" );
 		} );
 	}
 }