HHH-19604 fix Session.isDirty() with @Immutable entity

hibernate-core/src/main/java/org/hibernate/event/internal/DefaultDirtyCheckEventListener.java

@@ -4,6 +4,7 @@
  */
 package org.hibernate.event.internal;
 
+import org.hibernate.AssertionFailure;
 import org.hibernate.HibernateException;
 import org.hibernate.collection.spi.PersistentCollection;
 import org.hibernate.engine.spi.EntityEntry;
@@ -42,11 +43,7 @@ public void onDirtyCheck(DirtyCheckEvent event) throws HibernateException {
 		final var holdersByKey = persistenceContext.getEntityHoldersByKey();
 		if ( holdersByKey != null ) {
 			for ( var entry : holdersByKey.entrySet() ) {
-				final EntityHolder holder = entry.getValue();
-				final EntityEntry entityEntry = holder.getEntityEntry();
-				final Status status = entityEntry.getStatus();
-				if ( status != Status.MANAGED && status != Status.GONE
-					|| isEntityDirty( holder.getManagedObject(), holder.getDescriptor(), entityEntry, session ) ) {
+				if ( isEntityDirty( entry.getValue(), session ) ) {
 					event.setDirty( true );
 					return;
 				}
@@ -63,7 +60,18 @@ public void onDirtyCheck(DirtyCheckEvent event) throws HibernateException {
 		}
 	}
 
-	private static boolean isEntityDirty(
+	private static boolean isEntityDirty(EntityHolder holder, EventSource session) {
+		final EntityEntry entityEntry = holder.getEntityEntry();
+		final Status status = entityEntry.getStatus();
+		return switch ( status ) {
+			case GONE, READ_ONLY -> false;
+			case DELETED -> true;
+			case MANAGED -> isManagedEntityDirty( holder.getManagedObject(), holder.getDescriptor(), entityEntry, session );
+			case SAVING, LOADING -> throw new AssertionFailure( "Unexpected status: " + status );
+		};
+	}
+
+	private static boolean isManagedEntityDirty(
 			Object entity, EntityPersister descriptor, EntityEntry entityEntry, EventSource session) {
 		if ( entityEntry.requiresDirtyCheck( entity ) ) { // takes into account CustomEntityDirtinessStrategy
 			final Object[] propertyValues =

hibernate-core/src/test/java/org/hibernate/orm/test/IsDirtyImmutableTest.java

@@ -0,0 +1,48 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ * Copyright Red Hat Inc. and Hibernate Authors
+ */
+package org.hibernate.orm.test;
+
+import jakarta.persistence.Entity;
+import jakarta.persistence.Id;
+import jakarta.persistence.Table;
+import org.hibernate.annotations.Immutable;
+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.Test;
+
+import static org.junit.jupiter.api.Assertions.assertFalse;
+
+@SessionFactory
+@DomainModel(annotatedClasses = {IsDirtyImmutableTest.Mutable.class, IsDirtyImmutableTest.NotMutable.class})
+class IsDirtyImmutableTest {
+	@Test
+	void test(SessionFactoryScope scope) {
+		scope.inTransaction( s -> s.persist( new Mutable() ) );
+		scope.inTransaction( s -> {
+			var entity = s.find( NotMutable.class, 1L );
+			assertFalse( s.isDirty() );
+			entity.description = "new description";
+			assertFalse( s.isDirty() );
+		} );
+	}
+
+	@Entity
+	@Table(name = "TheTable")
+	static class Mutable {
+		@Id
+		Long id = 1L;
+		String description = "old description";
+	}
+
+	@Immutable
+	@Entity
+	@Table(name = "TheTable")
+	static class NotMutable {
+		@Id
+		Long id;
+		String description;
+	}
+}