Fix missing subclass discriminator in ON clause for entity joins (nhibernate#2600)

Fixes nhibernate#2599

Author: bahusoid

src/NHibernate.Test/Async/NHSpecificTest/GH2463/Fixture.cs

@@ -9,6 +9,7 @@
 
 
 using System.Linq;
+using NHibernate.Criterion;
 using NHibernate.DomainModel;
 using NUnit.Framework;
 using NHibernate.Linq;
@@ -19,23 +20,68 @@ namespace NHibernate.Test.NHSpecificTest.GH2463
 	[TestFixture]
 	public class FixtureAsync : TestCase
 	{
+		protected override bool AppliesTo(Dialect.Dialect dialect)
+		{
+			return Dialect.SupportsScalarSubSelects;
+		}
+
 		protected override string[] Mappings
 		{
 			get { return new[] {"ABC.hbm.xml"}; }
 		}
 
+		protected override void OnSetUp()
+		{
+			using (var session = OpenSession())
+			using (var transaction = session.BeginTransaction())
+			{
+				var a = new A {Name = "A", AnotherName = "X"};
+				session.Save(a);
+
+				var b = new B {Name = "B", AnotherName = "X"};
+				session.Save(b);
+
+				transaction.Commit();
+			}
+		}
+
+		protected override void OnTearDown()
+		{
+			using (var session = OpenSession())
+			using (var transaction = session.BeginTransaction())
+			{
+				session.CreateQuery("delete from System.Object").ExecuteUpdate();
+
+				transaction.Commit();
+			}
+		}
+
+		//Also see GH-2599
 		[Test]
-		public async Task CanJoinOnEntityWithDiscriminatorAsync()
+		public async Task CanJoinOnEntityWithDiscriminatorLinqAsync()
 		{
 			using (var s = OpenSession())
 			{
-				await (s.Query<A>().Join(
-					s.Query<A>(),
-					a => a.Id,
-					b => b.Id,
+				var list = await (s.Query<A>().Join(
+					s.Query<B>(),
+					a => a.AnotherName,
+					b => b.AnotherName,
 					(a, b) =>
 						new {a, b}).ToListAsync());
 			}
 		}
+
+		[Test]
+		public async Task CanJoinOnEntityWithDiscriminatorQueryOverAsync()
+		{
+			using (var s = OpenSession())
+			{
+				A a = null;
+				B b = null;
+				var list = await (s.QueryOver<A>(() => a)
+							.JoinEntityAlias(() => b, () => a.AnotherName == b.AnotherName)
+							.Select((x) => a.AsEntity(), (x) => b.AsEntity()).ListAsync<object[]>());
+			}
+		}
 	}
 }

src/NHibernate.Test/NHSpecificTest/GH2463/Fixture.cs

@@ -1,4 +1,5 @@
 using System.Linq;
+using NHibernate.Criterion;
 using NHibernate.DomainModel;
 using NUnit.Framework;
 
@@ -7,23 +8,68 @@ namespace NHibernate.Test.NHSpecificTest.GH2463
 	[TestFixture]
 	public class Fixture : TestCase
 	{
+		protected override bool AppliesTo(Dialect.Dialect dialect)
+		{
+			return Dialect.SupportsScalarSubSelects;
+		}
+
 		protected override string[] Mappings
 		{
 			get { return new[] {"ABC.hbm.xml"}; }
 		}
 
+		protected override void OnSetUp()
+		{
+			using (var session = OpenSession())
+			using (var transaction = session.BeginTransaction())
+			{
+				var a = new A {Name = "A", AnotherName = "X"};
+				session.Save(a);
+
+				var b = new B {Name = "B", AnotherName = "X"};
+				session.Save(b);
+
+				transaction.Commit();
+			}
+		}
+
+		protected override void OnTearDown()
+		{
+			using (var session = OpenSession())
+			using (var transaction = session.BeginTransaction())
+			{
+				session.CreateQuery("delete from System.Object").ExecuteUpdate();
+
+				transaction.Commit();
+			}
+		}
+
+		//Also see GH-2599
 		[Test]
-		public void CanJoinOnEntityWithDiscriminator()
+		public void CanJoinOnEntityWithDiscriminatorLinq()
 		{
 			using (var s = OpenSession())
 			{
-				s.Query<A>().Join(
-					s.Query<A>(),
-					a => a.Id,
-					b => b.Id,
+				var list = s.Query<A>().Join(
+					s.Query<B>(),
+					a => a.AnotherName,
+					b => b.AnotherName,
 					(a, b) =>
 						new {a, b}).ToList();
 			}
 		}
+
+		[Test]
+		public void CanJoinOnEntityWithDiscriminatorQueryOver()
+		{
+			using (var s = OpenSession())
+			{
+				A a = null;
+				B b = null;
+				var list = s.QueryOver<A>(() => a)
+							.JoinEntityAlias(() => b, () => a.AnotherName == b.AnotherName)
+							.Select((x) => a.AsEntity(), (x) => b.AsEntity()).List<object[]>();
+			}
+		}
 	}
 }

src/NHibernate/Engine/JoinSequence.cs

@@ -193,9 +193,9 @@ internal virtual JoinFragment ToJoinFragment(
 				else
 				{
 					// NH Different behavior : NH1179 and NH1293
-					// Apply filters in Many-To-One association
+					// Apply filters for entity joins and Many-To-One association
 					var enabledForManyToOne = FilterHelper.GetEnabledForManyToOne(enabledFilters);
-					condition = new SqlString(string.IsNullOrEmpty(on) && enabledForManyToOne.Count > 0
+					condition = new SqlString(string.IsNullOrEmpty(on) && (ForceFilter || enabledForManyToOne.Count > 0)
 					            	? join.Joinable.FilterFragment(join.Alias, enabledForManyToOne)
 					            	: on);
 				}
@@ -327,5 +327,7 @@ public interface ISelector
 		internal string RootAlias => rootAlias;
 
 		public ISessionFactoryImplementor Factory => factory;
+
+		internal bool ForceFilter { get; set; }
 	}
 }

src/NHibernate/Hql/Ast/ANTLR/Tree/EntityJoinFromElement.cs

@@ -18,7 +18,7 @@ public EntityJoinFromElement(FromClause fromClause, IQueryable entityPersister,
 			InitializeEntity(fromClause, entityPersister.EntityName, entityPersister, entityType, alias, tableAlias);
 
 			//NH Specific: hibernate uses special class EntityJoinJoinSequenceImpl
-			JoinSequence = new JoinSequence(SessionFactoryHelper.Factory)
+			JoinSequence = new JoinSequence(SessionFactoryHelper.Factory) {ForceFilter = true}
 				.AddJoin(entityType, tableAlias, joinType, Array.Empty<string>());
 
 			fromClause.Walker.AddQuerySpaces(entityPersister.QuerySpaces);

src/NHibernate/Loader/JoinWalker.cs

@@ -388,7 +388,8 @@ internal void AddExplicitEntityJoinAssociation(
 					GetWithClause(path, pathAlias),
 					Factory,
 					enabledFilters,
-					GetSelectMode(path)), path);
+					GetSelectMode(path)) {ForceFilter = true},
+				path);
 			AddAssociation(assoc);
 		}
 
@@ -851,8 +852,8 @@ protected JoinFragment MergeOuterJoins(IList<OuterJoinableAssociation> associati
 				{
 					oj.AddJoins(outerjoin);
 					// NH Different behavior : NH1179 and NH1293
-					// Apply filters in Many-To-One association
-					if (enabledFiltersForManyToOne.Count > 0)
+					// Apply filters for entity joins and Many-To-One associations
+					if (oj.ForceFilter || enabledFiltersForManyToOne.Count > 0)
 					{
 						string manyToOneFilterFragment = oj.Joinable.FilterFragment(oj.RHSAlias, enabledFiltersForManyToOne);
 						bool joinClauseDoesNotContainsFilterAlready =

src/NHibernate/Loader/OuterJoinableAssociation.cs

@@ -100,6 +100,8 @@ public SelectMode SelectMode
 
 		public ISet<string> EntityFetchLazyProperties { get; set; }
 
+		internal bool ForceFilter { get; set; }
+
 		public int GetOwner(IList<OuterJoinableAssociation> associations)
 		{
 			if (IsEntityType || IsCollection)