Add cross join support for Hql and Linq query provider (#2327)

Fixes: #1128, closes #1060

Author: maca88

src/NHibernate.Test/Async/FetchLazyProperties/FetchLazyPropertiesFixture.cs

@@ -9,12 +9,14 @@
 
 
 using System;
+using System.Collections.Generic;
 using System.Linq;
 using NHibernate.Cache;
 using NHibernate.Cfg;
 using NHibernate.Hql.Ast.ANTLR;
 using NHibernate.Linq;
 using NUnit.Framework;
+using NUnit.Framework.Constraints;
 using Environment = NHibernate.Cfg.Environment;
 
 namespace NHibernate.Test.FetchLazyProperties
@@ -943,6 +945,42 @@ public async Task TestFetchAfterEntityIsInitializedAsync(bool readOnly)
 			Assert.That(NHibernateUtil.IsPropertyInitialized(person, "Formula"), Is.True);
 		}
 
+		[Test]
+		public async Task TestHqlCrossJoinFetchFormulaAsync()
+		{
+			if (!Dialect.SupportsCrossJoin)
+			{
+				Assert.Ignore("Dialect does not support cross join.");
+			}
+
+			var persons = new List<Person>();
+			var bestFriends = new List<Person>();
+			using (var sqlSpy = new SqlLogSpy())
+			using (var s = OpenSession())
+			{
+				var list = await (s.CreateQuery("select p, bf from Person p cross join Person bf fetch bf.Formula where bf.Id = p.BestFriend.Id").ListAsync<object[]>());
+				foreach (var arr in list)
+				{
+					persons.Add((Person) arr[0]);
+					bestFriends.Add((Person) arr[1]);
+				}
+			}
+
+			AssertPersons(persons, false);
+			AssertPersons(bestFriends, true);
+
+			void AssertPersons(List<Person> results, bool fetched)
+			{
+				foreach (var person in results)
+				{
+					Assert.That(person, Is.Not.Null);
+					Assert.That(NHibernateUtil.IsPropertyInitialized(person, "Image"), Is.False);
+					Assert.That(NHibernateUtil.IsPropertyInitialized(person, "Address"), Is.False);
+					Assert.That(NHibernateUtil.IsPropertyInitialized(person, "Formula"), fetched ? Is.True : (IResolveConstraint) Is.False);
+				}
+			}
+		}
+
 		private static Person GeneratePerson(int i, Person bestFriend)
 		{
 			return new Person

src/NHibernate.Test/Async/Hql/EntityJoinHqlTest.cs

@@ -274,6 +274,27 @@ public async Task EntityJoinWithFetchesAsync()
 			}
 		}
 
+		[Test]
+		public async Task CrossJoinAndWhereClauseAsync()
+		{
+			using (var sqlLog = new SqlLogSpy())
+			using (var session = OpenSession())
+			{
+				var result = await (session.CreateQuery(
+					"SELECT s " +
+					"FROM EntityComplex s cross join EntityComplex q " +
+					"where s.SameTypeChild.Id = q.SameTypeChild.Id"
+				).ListAsync());
+
+				Assert.That(result, Has.Count.EqualTo(1));
+				Assert.That(sqlLog.Appender.GetEvents().Length, Is.EqualTo(1), "Only one SQL select is expected");
+				if (Dialect.SupportsCrossJoin)
+				{
+					Assert.That(sqlLog.GetWholeLog(), Does.Contain("cross join"), "A cross join is expected in the SQL select");
+				}
+			}
+		}
+
 		#region Test Setup
 
 		protected override HbmMapping GetMappings()

src/NHibernate.Test/Async/Linq/ByMethod/JoinTests.cs

@@ -8,7 +8,13 @@
 //------------------------------------------------------------------------------
 
 
+using System;
 using System.Linq;
+using System.Reflection;
+using NHibernate.Cfg;
+using NHibernate.Engine.Query;
+using NHibernate.Util;
+using NSubstitute;
 using NUnit.Framework;
 using NHibernate.Linq;
 
@@ -31,5 +37,32 @@ public async Task MultipleLinqJoinsWithSameProjectionNamesAsync()
 			Assert.That(orders.Count, Is.EqualTo(828));
 			Assert.IsTrue(orders.All(x => x.FirstId == x.SecondId - 1 && x.SecondId == x.ThirdId - 1));
 		}
+
+		[TestCase(false)]
+		[TestCase(true)]
+		public async Task CrossJoinWithPredicateInWhereStatementAsync(bool useCrossJoin)
+		{
+			if (useCrossJoin && !Dialect.SupportsCrossJoin)
+			{
+				Assert.Ignore("Dialect does not support cross join.");
+			}
+
+			using (var substitute = SubstituteDialect())
+			using (var sqlSpy = new SqlLogSpy())
+			{
+				ClearQueryPlanCache();
+				substitute.Value.SupportsCrossJoin.Returns(useCrossJoin);
+
+				var result = await ((from o in db.Orders
+							from o2 in db.Orders.Where(x => x.Freight > 50)
+							where (o.OrderId == o2.OrderId + 1) || (o.OrderId == o2.OrderId - 1)
+							select new { o.OrderId, OrderId2 = o2.OrderId }).ToListAsync());
+
+				var sql = sqlSpy.GetWholeLog();
+				Assert.That(result.Count, Is.EqualTo(720));
+				Assert.That(sql, Does.Contain(useCrossJoin ? "cross join" : "inner join"));
+				Assert.That(GetTotalOccurrences(sql, "inner join"), Is.EqualTo(useCrossJoin ? 0 : 1));
+			}
+		}
 	}
 }