Fix to #7289 - Query : Compilation error for queries with optional na…

…vigation, client side method and parameter

Problem was that DefaultQueryExpressionVisitor was not visiting extension expressions. During optional navigations we introduced NullConditional expressions to protect against null references - fix is to visit this expression as well.

src/Microsoft.EntityFrameworkCore.Specification.Tests/GearsOfWarQueryTestBase.cs

@@ -2159,6 +2159,24 @@ public virtual void Non_flattened_GroupJoin_with_result_operator_evaluates_on_th
             }
         }
 
+        [ConditionalFact]
+        public virtual void Client_side_equality_with_parameter_works_with_optional_navigations()
+        {
+            using (var context = CreateContext())
+            {
+                var prm = "Marcus's Tag";
+                var query = context.Gears.Where(g => ClientEquals(g.Tag.Note, prm));
+
+                var result = query.ToList();
+
+                Assert.Equal(1, result.Count);
+                Assert.Equal("Marcus", result[0].Nickname);
+            }
+        }
+
+        private static bool ClientEquals(string first, string second)
+            => first == second;
+
         protected GearsOfWarContext CreateContext() => Fixture.CreateContext(TestStore);
 
         protected GearsOfWarQueryTestBase(TFixture fixture)

src/Microsoft.EntityFrameworkCore/Query/ExpressionVisitors/Internal/DefaultQueryExpressionVisitor.cs

@@ -2,9 +2,11 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
+using System.Diagnostics;
 using System.Linq.Expressions;
 using System.Reflection;
 using JetBrains.Annotations;
+using Microsoft.EntityFrameworkCore.Query.Expressions.Internal;
 using Microsoft.EntityFrameworkCore.Query.Internal;
 using Microsoft.EntityFrameworkCore.Utilities;
 using Remotion.Linq.Clauses.Expressions;
@@ -77,6 +79,31 @@ protected override Expression VisitParameter(ParameterExpression node)
             return node;
         }
 
+        /// <summary>
+        ///     This API supports the Entity Framework Core infrastructure and is not intended to be used
+        ///     directly from your code. This API may change or be removed in future releases.
+        /// </summary>
+        protected override Expression VisitExtension(Expression node)
+        {
+            var nullConditionalExpression = node as NullConditionalExpression;
+            if (nullConditionalExpression != null)
+            {
+                var newNullableCaller = Visit(nullConditionalExpression.NullableCaller);
+                var newCaller = Visit(nullConditionalExpression.Caller);
+                var newAccessOperation = Visit(nullConditionalExpression.AccessOperation);
+
+                return newNullableCaller != nullConditionalExpression.NullableCaller
+                    || newCaller != nullConditionalExpression.Caller
+                    || newAccessOperation != nullConditionalExpression.AccessOperation
+                    ? new NullConditionalExpression(newNullableCaller, newCaller, newAccessOperation)
+                    : node;
+            }
+
+            Debug.Assert(false, "Unexpected extension expression: " + node);
+
+            return base.VisitExtension(node);
+        }
+
         /// <summary>
         ///     This API supports the Entity Framework Core infrastructure and is not intended to be used
         ///     directly from your code. This API may change or be removed in future releases.

test/Microsoft.EntityFrameworkCore.SqlServer.FunctionalTests/GearsOfWarQuerySqlServerTest.cs

@@ -2160,6 +2160,19 @@ public override void Non_flattened_GroupJoin_with_result_operator_evaluates_on_t
                 Sql);
         }
 
+        public override void Client_side_equality_with_parameter_works_with_optional_navigations()
+        {
+            base.Client_side_equality_with_parameter_works_with_optional_navigations();
+
+            Assert.Equal(
+                @"SELECT [g].[Nickname], [g].[SquadId], [g].[AssignedCityName], [g].[CityOrBirthName], [g].[Discriminator], [g].[FullName], [g].[HasSoulPatch], [g].[LeaderNickname], [g].[LeaderSquadId], [g].[Rank], [g.Tag].[Id], [g.Tag].[GearNickName], [g.Tag].[GearSquadId], [g.Tag].[Note]
+FROM [Gear] AS [g]
+LEFT JOIN [CogTag] AS [g.Tag] ON ([g].[Nickname] = [g.Tag].[GearNickName]) AND ([g].[SquadId] = [g.Tag].[GearSquadId])
+WHERE [g].[Discriminator] IN (N'Officer', N'Gear')
+ORDER BY [g].[Nickname], [g].[SquadId]",
+                Sql);
+        }
+
         protected override void ClearLog() => TestSqlLoggerFactory.Reset();
 
         private const string FileLineEnding = @"