Fix parameter caching for Linq provider

src/NHibernate.Test/Async/Linq/ConstantTest.cs

@@ -22,6 +22,7 @@
 namespace NHibernate.Test.Linq
 {
 	using System.Threading.Tasks;
+	using System.Threading;
 	// Mainly adapted from tests contributed by Nicola Tuveri on NH-2500 (NH-2500.patch file)
 	[TestFixture]
 	public class ConstantTestAsync : LinqTestCase
@@ -118,6 +119,29 @@ public async Task ConstantNonCachedInMemberInitExpressionAsync()
 			Assert.That(s2, Has.All.Property("Name").EqualTo("shipper2"), "s2 Names");
 		}
 
+		[Test]
+		public async Task ConstantNonCachedInMemberInitExpressionWithConditionAsync()
+		{
+			var shipper1 = await (GetShipperAsync(1));
+			var shipper2 = await (GetShipperAsync(2));
+
+			Assert.That(shipper1.Number, Is.EqualTo(1));
+			Assert.That(shipper2.Number, Is.EqualTo(2));
+		}
+
+		private Task<ShipperDto> GetShipperAsync(int id, CancellationToken cancellationToken = default(CancellationToken))
+		{
+			try
+			{
+				return db.Shippers.Where(o => o.ShipperId == id)
+				         .Select(o => new ShipperDto {Number = id, CompanyName = o.CompanyName}).SingleAsync(cancellationToken);
+			}
+			catch (System.Exception ex)
+			{
+				return Task.FromException<ShipperDto>(ex);
+			}
+		}
+
 		[Test]
 		public async Task ConstantInNewArrayExpressionAsync()
 		{

src/NHibernate.Test/Linq/ConstantTest.cs

@@ -120,6 +120,22 @@ public void ConstantNonCachedInMemberInitExpression()
 			Assert.That(s2, Has.All.Property("Name").EqualTo("shipper2"), "s2 Names");
 		}
 
+		[Test]
+		public void ConstantNonCachedInMemberInitExpressionWithCondition()
+		{
+			var shipper1 = GetShipper(1);
+			var shipper2 = GetShipper(2);
+
+			Assert.That(shipper1.Number, Is.EqualTo(1));
+			Assert.That(shipper2.Number, Is.EqualTo(2));
+		}
+
+		private ShipperDto GetShipper(int id)
+		{
+			return db.Shippers.Where(o => o.ShipperId == id)
+			         .Select(o => new ShipperDto {Number = id, CompanyName = o.CompanyName}).Single();
+		}
+
 		[Test]
 		public void ConstantInNewArrayExpression()
 		{

src/NHibernate/Linq/NhLinqExpression.cs

@@ -101,7 +101,7 @@ public IASTNode Translate(ISessionFactoryImplementor sessionFactory, bool filter
 
 			ParameterDescriptors = requiredHqlParameters.AsReadOnly();
 
-			CanCachePlan = CanCachePlan &&
+			CanCachePlan = CanCachePlan && visitorParameters.CanCachePlan &&
 				// If some constants do not have matching HQL parameters, their values from first query will
 				// be embedded in the plan and reused for subsequent queries: do not cache the plan.
 				!ParameterValuesByName

src/NHibernate/Linq/Visitors/SelectClauseNominator.cs

@@ -4,6 +4,7 @@
 using NHibernate.Engine;
 using NHibernate.Linq.Functions;
 using NHibernate.Linq.Expressions;
+using NHibernate.Param;
 using NHibernate.Util;
 using Remotion.Linq.Parsing;
 
@@ -17,6 +18,7 @@ class SelectClauseHqlNominator : RelinqExpressionVisitor
 	{
 		private readonly ILinqToHqlGeneratorsRegistry _functionRegistry;
 		private readonly ISessionFactoryImplementor _sessionFactory;
+		private readonly VisitorParameters _parameters;
 
 		/// <summary>
 		/// The expression parts that can be converted to pure HQL.
@@ -38,6 +40,7 @@ public SelectClauseHqlNominator(VisitorParameters parameters)
 		{
 			_functionRegistry = parameters.SessionFactory.Settings.LinqToHqlGeneratorsRegistry;
 			_sessionFactory = parameters.SessionFactory;
+			_parameters = parameters;
 		}
 
 		internal Expression Nominate(Expression expression)
@@ -152,6 +155,11 @@ private bool CanBeEvaluatedInHqlSelectStatement(Expression expression, bool proj
 			// Constants will only be evaluated in HQL if they're inside a method call
 			if (expression.NodeType == ExpressionType.Constant)
 			{
+				if (!projectConstantsInHql && _parameters.ConstantToParameterMap.ContainsKey((ConstantExpression)expression))
+				{
+					_parameters.CanCachePlan = false;
+				}
+
 				return projectConstantsInHql;
 			}
 

src/NHibernate/Linq/Visitors/VisitorParameters.cs

@@ -23,6 +23,8 @@ public class VisitorParameters
 
 		public QueryMode RootQueryMode { get; }
 
+		internal bool CanCachePlan { get; set; } = true;
+
 		public VisitorParameters(
 			ISessionFactoryImplementor sessionFactory, 
 			IDictionary<ConstantExpression, NamedParameter> constantToParameterMap, 
@@ -39,4 +41,4 @@ public VisitorParameters(
 			RootQueryMode = rootQueryMode;
 		}
 	}
-}
+}