Fix fetching lazy component with formula

src/NHibernate.Test/Async/NHSpecificTest/GH3164/FixtureByCode.cs

@@ -0,0 +1,66 @@
+//------------------------------------------------------------------------------
+// <auto-generated>
+//     This code was generated by AsyncGenerator.
+//
+//     Changes to this file may cause incorrect behavior and will be lost if
+//     the code is regenerated.
+// </auto-generated>
+//------------------------------------------------------------------------------
+
+
+using System.Linq;
+using NHibernate.Cfg.MappingSchema;
+using NHibernate.Mapping.ByCode;
+using NUnit.Framework;
+using NHibernate.Linq;
+
+namespace NHibernate.Test.NHSpecificTest.GH3164
+{
+	using System.Threading.Tasks;
+	[TestFixture]
+	public class ByCodeFixtureAsync : TestCaseMappingByCode
+	{
+		protected override HbmMapping GetMappings()
+		{
+			var mapper = new ModelMapper();
+			mapper.AddMapping<ContentItemMapping>();
+			mapper.AddMapping<HeadMapping>();
+
+			return mapper.CompileMappingForAllExplicitlyAddedEntities();
+		}
+
+		protected override void OnSetUp()
+		{
+			using (var session = OpenSession())
+			using (var transaction = session.BeginTransaction())
+			{
+				var e1 = new ContentItem { Name = "Test" };
+				session.Save(e1);
+
+				transaction.Commit();
+			}
+		}
+
+		protected override void OnTearDown()
+		{
+			using (var session = OpenSession())
+			using (var transaction = session.BeginTransaction())
+			{
+				session.CreateQuery("delete from System.Object").ExecuteUpdate();
+
+				transaction.Commit();
+			}
+		}
+
+		[Test]
+		public async Task FetchComponentAsync()
+		{
+			using (var session = OpenSession())
+			{
+				var result = await (session.Query<ContentItem>().Fetch(i => i.Head).ToListAsync());
+
+				Assert.That(result.Count, Is.EqualTo(1));
+			}
+		}
+	}
+}

src/NHibernate.Test/NHSpecificTest/GH3164/ContentItem.cs

@@ -0,0 +1,9 @@
+namespace NHibernate.Test.NHSpecificTest.GH3164
+{
+	public class ContentItem
+	{
+		public virtual int Id { get; set; }
+		public virtual string Name { get; set; }
+		public virtual IHead Head { get; set; }
+	}
+}

src/NHibernate.Test/NHSpecificTest/GH3164/ContentItemMapping.cs

@@ -0,0 +1,16 @@
+using NHibernate.Mapping.ByCode;
+using NHibernate.Mapping.ByCode.Conformist;
+
+namespace NHibernate.Test.NHSpecificTest.GH3164
+{
+	public class ContentItemMapping : ClassMapping<ContentItem>
+	{
+		public ContentItemMapping()
+		{
+			Table("ContentItems");
+			Id(x => x.Id, m => m.Generator(Generators.Identity));
+			Property(x => x.Name);
+			Component(x => x.Head, x => x.Lazy(true));
+		}
+	}
+}

src/NHibernate.Test/NHSpecificTest/GH3164/FixtureByCode.cs

@@ -0,0 +1,55 @@
+using System.Linq;
+using NHibernate.Cfg.MappingSchema;
+using NHibernate.Mapping.ByCode;
+using NUnit.Framework;
+using NHibernate.Linq;
+
+namespace NHibernate.Test.NHSpecificTest.GH3164
+{
+	[TestFixture]
+	public class ByCodeFixture : TestCaseMappingByCode
+	{
+		protected override HbmMapping GetMappings()
+		{
+			var mapper = new ModelMapper();
+			mapper.AddMapping<ContentItemMapping>();
+			mapper.AddMapping<HeadMapping>();
+
+			return mapper.CompileMappingForAllExplicitlyAddedEntities();
+		}
+
+		protected override void OnSetUp()
+		{
+			using (var session = OpenSession())
+			using (var transaction = session.BeginTransaction())
+			{
+				var e1 = new ContentItem { Name = "Test" };
+				session.Save(e1);
+
+				transaction.Commit();
+			}
+		}
+
+		protected override void OnTearDown()
+		{
+			using (var session = OpenSession())
+			using (var transaction = session.BeginTransaction())
+			{
+				session.CreateQuery("delete from System.Object").ExecuteUpdate();
+
+				transaction.Commit();
+			}
+		}
+
+		[Test]
+		public void FetchComponent()
+		{
+			using (var session = OpenSession())
+			{
+				var result = session.Query<ContentItem>().Fetch(i => i.Head).ToList();
+
+				Assert.That(result.Count, Is.EqualTo(1));
+			}
+		}
+	}
+}

src/NHibernate.Test/NHSpecificTest/GH3164/Head.cs

@@ -0,0 +1,12 @@
+using System;
+
+namespace NHibernate.Test.NHSpecificTest.GH3164
+{
+	[Serializable]
+	public class Head : IHead
+	{
+		public virtual string Title { get; set; }
+
+		public virtual bool DummyFieldToLoadEmptyComponent { get; }
+	}
+}

src/NHibernate.Test/NHSpecificTest/GH3164/HeadMapping.cs

@@ -0,0 +1,24 @@
+using NHibernate.Mapping.ByCode;
+using NHibernate.Mapping.ByCode.Conformist;
+
+namespace NHibernate.Test.NHSpecificTest.GH3164
+{
+	public class HeadMapping : ComponentMapping<IHead>
+	{
+		public HeadMapping()
+		{
+			Class<Head>();
+			Property(x => x.Title, m =>
+			{
+				m.Column("PageTitle");
+				m.Lazy(true);
+			});
+			Property(x => x.DummyFieldToLoadEmptyComponent, m =>
+			{
+				m.Access(Accessor.ReadOnly);
+				m.Formula("1");
+			});
+			Lazy(true);
+		}
+	}
+}

src/NHibernate.Test/NHSpecificTest/GH3164/IHead.cs

@@ -0,0 +1,10 @@
+namespace NHibernate.Test.NHSpecificTest.GH3164
+{
+
+	public interface IHead
+	{
+		string Title { get; set; }
+
+		bool DummyFieldToLoadEmptyComponent { get; }
+	}
+}

src/NHibernate/Persister/Entity/AbstractEntityPersister.cs

@@ -1673,14 +1673,10 @@ private string PropertySelectFragment(string name, string suffix, ICollection<st
 					}
 
 					var columnNames = SubclassPropertyColumnNameClosure[index];
-					// Formulas will have all null values
-					if (columnNames.All(o => o == null))
-					{
-						columnNames = SubclassPropertyFormulaTemplateClosure[index];
-					}
 
-					foreach (var columnName in columnNames)
+					for (var i = 0; i < columnNames.Length; i++)
 					{
+						var columnName = columnNames[i] ?? SubclassPropertyFormulaTemplateClosure[index][i];
 						fetchColumnsAndFormulas.Add(columnName);
 					}
 				}