Fix GroupBy to custom class failing with ArgumentException (nhibernate#1705)

Fixes nhibernate#1704

Author: Antonis Mygiakis

src/NHibernate.Test/Async/NHSpecificTest/GH1704/Fixture.cs

@@ -0,0 +1,76 @@
+//------------------------------------------------------------------------------
+// <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 NUnit.Framework;
+using NHibernate.Linq;
+
+namespace NHibernate.Test.NHSpecificTest.GH1704
+{
+	using System.Threading.Tasks;
+	[TestFixture]
+	public class FixtureAsync : BugTestCase
+	{
+		protected override void OnSetUp()
+		{
+			using (var session = OpenSession())
+			using (var transaction = session.BeginTransaction())
+			{
+				var e1 = new Entity { Country = "Greece", City = "Athens", Budget = 100000m };
+				session.Save(e1);
+
+				var e2 = new Entity { Country = "Greece", City = "Chania", Budget = 50000m };
+				session.Save(e2);
+
+				var e3 = new Entity { Country = "Italy", City = "Rome", Budget = 200000m };
+				session.Save(e3);
+
+				var e4 = new Entity { Country = "Italy", City = "Milan", Budget = 100000m };
+				session.Save(e4);
+
+				var e5 = new Entity { Country = "France", City = "Paris", Budget = 300000m };
+				session.Save(e5);
+
+				transaction.Commit();
+			}
+		}
+
+		protected override void OnTearDown()
+		{
+			using (var session = OpenSession())
+			using (var transaction = session.BeginTransaction())
+			{
+				// The HQL delete does all the job inside the database without loading the entities, but it does
+				// not handle delete order for avoiding violating constraints if any. Use
+				// session.Delete("from System.Object");
+				// instead if in need of having NHbernate ordering the deletes, but this will cause
+				// loading the entities in the session.
+				session.CreateQuery("delete from System.Object").ExecuteUpdate();
+
+				transaction.Commit();
+			}
+		}
+
+		[Test(Description = "GH-1704")]
+		public async Task GroupByCustomClassAsKeyAsync()
+		{
+			using (var session = OpenSession())
+			using (session.BeginTransaction())
+			{
+				var result = await (session.Query<Entity>()
+				.GroupBy(a => new GroupByEntity(a.Country))
+				.Select(a => new { groupby = a.Key, cnt = a.Count(), sum = a.Sum(o => o.Budget) })
+				.ToListAsync());
+
+				Assert.That(result, Has.Count.EqualTo(3));
+			}
+		}
+	}
+}

src/NHibernate.Test/NHSpecificTest/GH1704/Entity.cs

@@ -0,0 +1,22 @@
+using System;
+
+namespace NHibernate.Test.NHSpecificTest.GH1704
+{
+	class Entity
+	{
+		public virtual Guid Id { get; set; }
+		public virtual string Country { get; set; }
+		public virtual string City { get; set; }
+		public virtual decimal Budget { get; set; }
+	}
+
+	class GroupByEntity
+	{
+		public GroupByEntity(string country)
+		{
+			Country = country;
+		}
+		public virtual string Country { get; set; }
+		public virtual string City { get; set; }
+	}
+}

src/NHibernate.Test/NHSpecificTest/GH1704/Fixture.cs

@@ -0,0 +1,64 @@
+using System.Linq;
+using NUnit.Framework;
+
+namespace NHibernate.Test.NHSpecificTest.GH1704
+{
+	[TestFixture]
+	public class Fixture : BugTestCase
+	{
+		protected override void OnSetUp()
+		{
+			using (var session = OpenSession())
+			using (var transaction = session.BeginTransaction())
+			{
+				var e1 = new Entity { Country = "Greece", City = "Athens", Budget = 100000m };
+				session.Save(e1);
+
+				var e2 = new Entity { Country = "Greece", City = "Chania", Budget = 50000m };
+				session.Save(e2);
+
+				var e3 = new Entity { Country = "Italy", City = "Rome", Budget = 200000m };
+				session.Save(e3);
+
+				var e4 = new Entity { Country = "Italy", City = "Milan", Budget = 100000m };
+				session.Save(e4);
+
+				var e5 = new Entity { Country = "France", City = "Paris", Budget = 300000m };
+				session.Save(e5);
+
+				transaction.Commit();
+			}
+		}
+
+		protected override void OnTearDown()
+		{
+			using (var session = OpenSession())
+			using (var transaction = session.BeginTransaction())
+			{
+				// The HQL delete does all the job inside the database without loading the entities, but it does
+				// not handle delete order for avoiding violating constraints if any. Use
+				// session.Delete("from System.Object");
+				// instead if in need of having NHbernate ordering the deletes, but this will cause
+				// loading the entities in the session.
+				session.CreateQuery("delete from System.Object").ExecuteUpdate();
+
+				transaction.Commit();
+			}
+		}
+
+		[Test(Description = "GH-1704")]
+		public void GroupByCustomClassAsKey()
+		{
+			using (var session = OpenSession())
+			using (session.BeginTransaction())
+			{
+				var result = session.Query<Entity>()
+				.GroupBy(a => new GroupByEntity(a.Country))
+				.Select(a => new { groupby = a.Key, cnt = a.Count(), sum = a.Sum(o => o.Budget) })
+				.ToList();
+
+				Assert.That(result, Has.Count.EqualTo(3));
+			}
+		}
+	}
+}

src/NHibernate.Test/NHSpecificTest/GH1704/Mappings.hbm.xml

@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<hibernate-mapping 
+	xmlns="urn:nhibernate-mapping-2.2" assembly="NHibernate.Test" namespace="NHibernate.Test.NHSpecificTest.GH1704">
+	<class name="Entity">
+		<id name="Id" generator="guid.comb"/>
+		<property name="Country"/>
+		<property name="City"/>
+		<property name="Budget"/>
+	</class>
+</hibernate-mapping>

src/NHibernate/Linq/GroupBy/GroupKeyNominator.cs

@@ -55,6 +55,9 @@ protected override Expression VisitNew(NewExpression expression)
 		{
 			_transformed = true;
 			// Transform each initializer recursively (to allow for nested initializers)
+			if (expression.Members == null)
+				return Expression.New(expression.Constructor, expression.Arguments.Select(VisitInternal));
+
 			return Expression.New(expression.Constructor, expression.Arguments.Select(VisitInternal), expression.Members);
 		}
 
@@ -85,4 +88,4 @@ protected override Expression VisitBinary(BinaryExpression expression)
 			return base.VisitBinary(expression);
 		}
 	}
-}
+}