Use ReplacingExpressionVisitor instead, add additional test for LeftJoin extension method

Author: maca88

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

@@ -93,6 +93,27 @@ public async Task MultipleLinqJoinsWithSameProjectionNamesWithLeftJoinExtensionM
 			}
 		}
 
+		[Test]
+		public async Task LeftJoinExtensionMethodWithMultipleKeyPropertiesAsync()
+		{
+			using (var sqlSpy = new SqlLogSpy())
+			{
+				var orders = await (db.Orders
+				               .LeftJoin(
+					               db.Orders,
+					               x => new {x.OrderId, x.Customer.CustomerId},
+					               x => new {x.OrderId, x.Customer.CustomerId},
+					               (order, order1) => new {order, order1})
+				               .Select(x => new {FirstId = x.order.OrderId, SecondId = x.order1.OrderId})
+				               .ToListAsync());
+
+				var sql = sqlSpy.GetWholeLog();
+				Assert.That(orders.Count, Is.EqualTo(830));
+				Assert.IsTrue(orders.All(x => x.FirstId == x.SecondId));
+				Assert.That(GetTotalOccurrences(sql, "left outer join"), Is.EqualTo(1));
+			}
+		}
+
 		[TestCase(false)]
 		[TestCase(true)]
 		public async Task CrossJoinWithPredicateInWhereStatementAsync(bool useCrossJoin)

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

@@ -82,6 +82,27 @@ public void MultipleLinqJoinsWithSameProjectionNamesWithLeftJoinExtensionMethod(
 			}
 		}
 
+		[Test]
+		public void LeftJoinExtensionMethodWithMultipleKeyProperties()
+		{
+			using (var sqlSpy = new SqlLogSpy())
+			{
+				var orders = db.Orders
+				               .LeftJoin(
+					               db.Orders,
+					               x => new {x.OrderId, x.Customer.CustomerId},
+					               x => new {x.OrderId, x.Customer.CustomerId},
+					               (order, order1) => new {order, order1})
+				               .Select(x => new {FirstId = x.order.OrderId, SecondId = x.order1.OrderId})
+				               .ToList();
+
+				var sql = sqlSpy.GetWholeLog();
+				Assert.That(orders.Count, Is.EqualTo(830));
+				Assert.IsTrue(orders.All(x => x.FirstId == x.SecondId));
+				Assert.That(GetTotalOccurrences(sql, "left outer join"), Is.EqualTo(1));
+			}
+		}
+
 		[TestCase(false)]
 		[TestCase(true)]
 		public void CrossJoinWithPredicateInWhereStatement(bool useCrossJoin)

src/NHibernate/Linq/LinqExtensionMethods.cs

@@ -2517,7 +2517,7 @@ public static IQueryable<TResult> LeftJoin<TOuter, TInner, TKey, TResult>(
 			var paramNew = Expression.Parameter(typeof(LeftJoinIntermediate<TOuter, TInner>));
 			var outerProperty = Expression.Property(paramNew, nameof(LeftJoinIntermediate<TOuter, TInner>.OneOuter));
 			var selectManyResultSelector = Expression.Lambda(
-				new Replacer(outerParameter, outerProperty).Visit(resultSelector.Body),
+				ReplacingExpressionVisitor.Replace(outerParameter, outerProperty, resultSelector.Body),
 				paramNew,
 				resultSelector.Parameters[1]);
 
@@ -2531,28 +2531,6 @@ private class LeftJoinIntermediate<TOuter, TInner>
 			public IEnumerable<TInner> ManyInners { get; set; }
 		}
 
-		private class Replacer : ExpressionVisitor
-		{
-			private readonly ParameterExpression _oldParam;
-			private readonly Expression _replacement;
-
-			public Replacer(ParameterExpression oldParam, Expression replacement)
-			{
-				_oldParam = oldParam;
-				_replacement = replacement;
-			}
-
-			public override Expression Visit(Expression exp)
-			{
-				if (exp == _oldParam)
-				{
-					return _replacement;
-				}
-
-				return base.Visit(exp);
-			}
-		}
-
 		#endregion
 
 		/// <summary>