Fix IsModified so that a null equates empty components when using select-before-update

src/NHibernate.Test/NHSpecificTest/GH1486/Entities.cs

@@ -0,0 +1,82 @@
+using System;
+
+
+namespace NHibernate.Test.NHSpecificTest.GH1486
+{
+	public class Person
+	{
+		public virtual int Id { get; set; }
+
+		public virtual string Name { get; set; }
+
+		public virtual Address Address { get; set; }
+
+		public virtual int Version { get; set; }
+
+		public Person()
+		{
+		}
+
+		public Person(int id, string name, Address address)
+		{
+			Id = id;
+			Name = name;
+			Address = address;
+		}
+	}
+
+	public class Address : IEquatable<Address>
+	{
+		public virtual string PostalCode { get; set; }
+
+		public virtual string State { get; set; }
+
+		public virtual string Street { get; set; }
+
+		public Address()
+		{ }
+
+		public Address(string postalCode, string state, string street)
+		{
+			PostalCode = postalCode;
+			State = state;
+			Street = street;
+		}
+
+		public bool Equals(Address other)
+		{
+			if (ReferenceEquals(null, other)) return false;
+			if (ReferenceEquals(this, other)) return true;
+			return string.Equals(Street, other.Street) && string.Equals(State, other.State) && string.Equals(PostalCode, other.PostalCode);
+		}
+
+		public override bool Equals(object obj)
+		{
+			if (ReferenceEquals(null, obj)) return false;
+			if (ReferenceEquals(this, obj)) return true;
+			if (obj.GetType() != GetType()) return false;
+			return Equals((Address) obj);
+		}
+
+		public override int GetHashCode()
+		{
+			unchecked
+			{
+				var hashCode = (PostalCode != null ? PostalCode.GetHashCode() : 0);
+				hashCode = (hashCode * 397) ^ (State != null ? State.GetHashCode() : 0);
+				hashCode = (hashCode * 397) ^ (Street != null ? Street.GetHashCode() : 0);
+				return hashCode;
+			}
+		}
+
+		public static bool operator ==(Address left, Address right)
+		{
+			return Equals(left, right);
+		}
+
+		public static bool operator !=(Address left, Address right)
+		{
+			return !Equals(left, right);
+		}
+	}
+}

src/NHibernate.Test/NHSpecificTest/GH1486/Fixture.cs

@@ -0,0 +1,145 @@
+using System.Linq;
+using NUnit.Framework;
+using NHibernate.Cfg;
+using NHibernate.Type;
+
+namespace NHibernate.Test.NHSpecificTest.GH1486
+{
+	[TestFixture]
+	public class Fixture : BugTestCase
+	{
+		private readonly OnFlushDirtyInterceptor _interceptor = new OnFlushDirtyInterceptor();
+
+		protected override void Configure(Configuration configuration)
+		{
+			base.Configure(configuration);
+			configuration.SetInterceptor(_interceptor);
+		}
+
+		protected override void OnSetUp()
+		{
+			using (var session = OpenSession())
+			{
+				using (var transaction = session.BeginTransaction())
+				{
+					var john = new Person(1, "John", new Address());
+					session.Save(john);
+
+					var mary = new Person(2, "Mary", null);
+					session.Save(mary);
+
+					var bob = new Person(3, "Bob", new Address("1", "A", "B"));
+					session.Save(bob);
+
+					session.Flush();
+					transaction.Commit();
+				}
+			}
+		}
+
+		protected override void OnTearDown()
+		{
+			using (var session = OpenSession())
+			using (var transaction = session.BeginTransaction())
+			{
+				session.Delete("from System.Object");
+				session.Flush();
+				transaction.Commit();
+			}
+		}
+
+		/// <summary>
+		/// The test case was imported from Hibernate HHH-11237 and adjusted for NHibernate. 
+		/// </summary>
+		[Test]
+		public void TestSelectBeforeUpdate()
+		{
+			using (var session = OpenSession())
+			{
+				using (var transaction = session.BeginTransaction())
+				{
+					var john = session.Get<Person>(1);
+					_interceptor.Reset();
+					john.Address = null;
+					session.Flush();
+					Assert.That(_interceptor.CallCount, Is.EqualTo(0), "unexpected flush dirty count for John");
+
+					_interceptor.Reset();
+					var mary = session.Get<Person>(2);
+					mary.Address = new Address();
+					session.Flush();
+					Assert.That(_interceptor.CallCount, Is.EqualTo(0), "unexpected flush dirty count for Mary");
+					transaction.Commit();
+				}
+			}
+
+			Person johnObj;
+			Person maryObj;
+			using (var session = OpenSession())
+			{
+				using (var transaction = session.BeginTransaction())
+				{
+					johnObj = session.Get<Person>(1);
+				}
+			}
+
+			using (var session = OpenSession())
+			{
+				using (var transaction = session.BeginTransaction())
+				{
+					maryObj = session.Get<Person>(2);
+				}
+			}
+
+			using (var session = OpenSession())
+			{
+				using (var transaction = session.BeginTransaction())
+				{
+					_interceptor.Reset();
+					johnObj.Address = null;
+					session.Update(johnObj);
+					session.Flush();
+					Assert.That(_interceptor.CallCount, Is.EqualTo(0), "unexpected flush dirty count for John update");
+
+					_interceptor.Reset();
+					maryObj.Address = new Address();
+					session.Update(maryObj);
+					session.Flush();
+					Assert.That(_interceptor.CallCount, Is.EqualTo(0), "unexpected flush dirty count for Mary update");
+					transaction.Commit();
+				}
+			}
+		}
+
+		[Test]
+		public void TestDirectCallToIsModified()
+		{
+			using (var session = OpenSession())
+			using (var transaction = session.BeginTransaction())
+			{
+				var person = session.Load<Person>(3);
+				Assert.That(person, Is.Not.Null, "Bob is not found.");
+				Assert.That(person.Address, Is.Not.Null, "Bob's address is missing.");
+				var sessionImplementor = session.GetSessionImplementation();
+
+				var metaData = session.SessionFactory.GetClassMetadata(typeof(Person));
+				foreach (var propertyType in metaData.PropertyTypes)
+				{
+					if (!(propertyType is ComponentType componentType) || componentType.ReturnedClass.Name != "Address")
+						continue;
+
+					var checkable = new [] { true, true, true };
+					Assert.That(
+						() => componentType.IsModified(new object[] { "", "", "" }, person.Address, checkable, sessionImplementor),
+						Throws.Nothing,
+						"Checking component against an array snapshot failed");
+					var isModified = componentType.IsModified(person.Address, person.Address, checkable, sessionImplementor);
+					Assert.That(isModified, Is.False, "Checking same component failed");
+					isModified = componentType.IsModified(new Address("1", "A", "B"), person.Address, checkable, sessionImplementor);
+					Assert.That(isModified, Is.False, "Checking equal component failed");
+				}
+				transaction.Rollback();
+			}
+		}
+	}
+}

src/NHibernate.Test/NHSpecificTest/GH1486/Mappings.hbm.xml

@@ -0,0 +1,15 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" assembly="NHibernate.Test" namespace="NHibernate.Test.NHSpecificTest.GH1486">
+
+  <class name="Person" select-before-update="true">
+    <id name="Id" type="integer" />
+    <property name="Name" type="string" length="50"/>
+    <property name="Version" type="integer" />
+    <component name="Address">
+      <property name="PostalCode" type="string" length="20" />
+      <property name="Street" type="string" length="100" />
+      <property name="State" type="string" length="50" />
+    </component>
+  </class>
+
+</hibernate-mapping>

src/NHibernate.Test/NHSpecificTest/GH1486/OnFlushDirtyInterceptor.cs

@@ -0,0 +1,20 @@
+using NHibernate.Type;
+
+namespace NHibernate.Test.NHSpecificTest.GH1486
+{
+	public class OnFlushDirtyInterceptor : EmptyInterceptor
+	{
+		public int CallCount = 0;
+
+		public override bool OnFlushDirty(object entity, object id, object[] currentState, object[] previousState, string[] propertyNames, IType[] types)
+		{
+			CallCount++;
+			return false;
+		}
+
+		public void Reset()
+		{
+			CallCount = 0;
+		}
+	}
+}

src/NHibernate/Tuple/Component/AbstractComponentTuplizer.cs

@@ -101,7 +101,8 @@ public virtual void SetPropertyValues(object component, object[] values)
 
 		public virtual object GetPropertyValue(object component, int i)
 		{
-			return getters[i].Get(component);
+			// NH Different behavior : for NH-1101
+			return component == null ? null : getters[i].Get(component);
 		}
 
 		/// <summary> This method does not populate the component parent</summary>

src/NHibernate/Type/ComponentType.cs

@@ -525,16 +525,12 @@ public override object SemiResolve(object value, ISessionImplementor session, ob
 
 		public override bool IsModified(object old, object current, bool[] checkable, ISessionImplementor session)
 		{
-			if (current == null)
+			if (old == current)
 			{
-				return old != null;
-			}
-			if (old == null)
-			{
-				return current != null;
+				return false;
 			}
 			object[] currentValues = GetPropertyValues(current, session);
-			object[] oldValues = (Object[]) old;
+			var oldValues = old is object[] objects ? objects : GetPropertyValues(old, session);
 			int loc = 0;
 			for (int i = 0; i < currentValues.Length; i++)
 			{