Fix to #12314 - SumAsync throw Exception when used over float?

Problem was that in order to return 0 from empty Sum of nullable values, we convert them to non-nullable (to produce 0) and then convert back to nullable type. This works without issue for sync path, but in async simple casting like that doesn't work.

Fix is to call method that adds Task.ContinueWith() call that casts the result to the correct type in the async scenario.

src/EFCore.Relational/Extensions/TaskExtensions.cs → src/EFCore.Relational/Extensions/RelationalTaskExtensions.cs

@@ -3,7 +3,7 @@
 
 namespace System.Threading.Tasks
 {
-    internal static class TaskExtensions
+    internal static class RelationalTaskExtensions
     {
         public static Task<TDerived> Cast<T, TDerived>(this Task<T> task)
             where TDerived : T
@@ -31,5 +31,32 @@ public static Task<TDerived> Cast<T, TDerived>(this Task<T> task)
 
             return taskCompletionSource.Task;
         }
+
+        public static Task<T?> CastToNullable<T>(this Task<T> task)
+            where T : struct
+        {
+            var taskCompletionSource = new TaskCompletionSource<T?>();
+
+            task.ContinueWith(
+                t =>
+                {
+                    if (t.IsFaulted)
+                    {
+                        // ReSharper disable once PossibleNullReferenceException
+                        taskCompletionSource.TrySetException(t.Exception.InnerExceptions);
+                    }
+                    else if (t.IsCanceled)
+                    {
+                        taskCompletionSource.TrySetCanceled();
+                    }
+                    else
+                    {
+                        taskCompletionSource.TrySetResult((T?)t.Result);
+                    }
+                },
+                TaskContinuationOptions.ExecuteSynchronously);
+
+            return taskCompletionSource.Task;
+        }
     }
 }

src/EFCore.Relational/Query/Internal/RelationalResultOperatorHandler.cs

@@ -963,6 +963,9 @@ var sqlTranslatingExpressionVisitor
             return handlerContext.EvalOnClient();
         }
 
+        private static readonly MethodInfo _castToNullableMethodInfo
+            = typeof(RelationalTaskExtensions).GetRuntimeMethods().Where(m => m.Name == nameof(RelationalTaskExtensions.CastToNullable)).Single();
+
         private static Expression HandleSum(HandlerContext handlerContext)
         {
             if (!handlerContext.QueryModelVisitor.RequiresClientProjection
@@ -990,10 +993,21 @@ var clientExpression
                             .MakeGenericMethod(sumExpression.Type.UnwrapNullableType())
                             .Invoke(null, new object[] { handlerContext, /*throwOnNullResult:*/ false });
 
-                    return
-                        sumExpression.Type.IsNullableType()
+                    if (handlerContext.QueryModelVisitor.QueryCompilationContext.IsAsyncQuery
+                        && !(AppContext.TryGetSwitch("Microsoft.EntityFrameworkCore.Issue12314", out var isEnabled) && isEnabled))
+                    {
+                        return sumExpression.Type.IsNullableType()
+                            ? Expression.Call(
+                                _castToNullableMethodInfo.MakeGenericMethod(sumExpression.Type.UnwrapNullableType()),
+                                clientExpression)
+                            : clientExpression;
+                    }
+                    else
+                    {
+                        return sumExpression.Type.IsNullableType()
                             ? Expression.Convert(clientExpression, sumExpression.Type)
                             : clientExpression;
+                    }
                 }
             }
 

src/EFCore.Specification.Tests/Query/AsyncGearsOfWarQueryTestBase.cs

@@ -1691,5 +1691,15 @@ await AssertQuery<City>(
                 assertOrder: true,
                 elementAsserter: CollectionAsserter<Gear>(e => e.Nickname, (e, a) => Assert.Equal(e.Nickname, a.Nickname)));
         }
+
+        [ConditionalFact]
+        public virtual async Task Sum_with_no_data_nullable_double()
+        {
+            using (var ctx = CreateContext())
+            {
+                var result = await ctx.Missions.Where(m => m.CodeName == "Operation Foobar").Select(m => m.Rating).SumAsync();
+                Assert.Equal(0, result);
+            }
+        }
     }
 }

src/EFCore.Specification.Tests/Query/AsyncSimpleQueryTestBase.cs

@@ -3808,5 +3808,11 @@ public virtual async Task Cast_to_same_Type_CountAsync_works()
         {
             await AssertSingleResult<Customer>(cs => cs.Cast<Customer>().CountAsync());
         }
+
+        [ConditionalFact]
+        public virtual async Task Sum_with_no_data_nullable()
+        {
+            await AssertSingleResult<Order>(os => os.Where(o => o.OrderID < 0).Select(o => (int?)o.OrderID).SumAsync());
+        }
     }
 }

src/EFCore.Specification.Tests/Query/GearsOfWarQueryFixtureBase.cs

@@ -150,6 +150,7 @@ protected GearsOfWarQueryFixtureBase()
                             {
                                 Assert.Equal(e.Id, a.Id);
                                 Assert.Equal(e.CodeName, a.CodeName);
+                                Assert.Equal(e.Rating, a.Rating);
                                 Assert.Equal(e.Timeline, a.Timeline);
                             }
                         }

src/EFCore.Specification.Tests/TestModels/GearsOfWarModel/GearsOfWarData.cs

@@ -104,9 +104,9 @@ public static IReadOnlyList<Squad> CreateSquads()
         public static IReadOnlyList<Mission> CreateMissions()
             => new List<Mission>
             {
-                new Mission { Id = 1, CodeName = "Lightmass Offensive", Timeline = new DateTimeOffset(2, 1, 2, 10, 0, 0, new TimeSpan(1, 30, 0)) },
-                new Mission { Id = 2, CodeName = "Hollow Storm", Timeline = new DateTimeOffset(2, 3, 1, 8, 0, 0, new TimeSpan(-5, 0, 0)) },
-                new Mission { Id = 3, CodeName = "Halvo Bay defense", Timeline = new DateTimeOffset(10, 5, 3, 12, 0, 0, new TimeSpan()) }
+                new Mission { Id = 1, CodeName = "Lightmass Offensive", Rating = 2.1, Timeline = new DateTimeOffset(2, 1, 2, 10, 0, 0, new TimeSpan(1, 30, 0)) },
+                new Mission { Id = 2, CodeName = "Hollow Storm", Rating = 4.2, Timeline = new DateTimeOffset(2, 3, 1, 8, 0, 0, new TimeSpan(-5, 0, 0)) },
+                new Mission { Id = 3, CodeName = "Halvo Bay defense", Rating = null, Timeline = new DateTimeOffset(10, 5, 3, 12, 0, 0, new TimeSpan()) }
             };
 
         public static IReadOnlyList<SquadMission> CreateSquadMissions()

src/EFCore.Specification.Tests/TestModels/GearsOfWarModel/Mission.cs

@@ -11,6 +11,7 @@ public class Mission
         public int Id { get; set; }
 
         public string CodeName { get; set; }
+        public double? Rating { get; set; }
         public DateTimeOffset Timeline { get; set; }
 
         public virtual ICollection<SquadMission> ParticipatingSquads { get; set; }

test/EFCore.SqlServer.FunctionalTests/Query/AsyncSimpleQuerySqlServerTest.cs

@@ -214,5 +214,21 @@ await AssertQuery<Order>(
                 os => os.Select(o => new { o.Customer.City, Count = o.OrderDetails.Count() }),
                 elementSorter: e => e.City + " " + e.Count);
         }
+
+        [Fact]
+        public async Task Sum_with_no_data_nullable_legacy_behavior()
+        {
+            AppContext.SetSwitch("Microsoft.EntityFrameworkCore.Issue12314", true);
+
+            try
+            {
+                await Assert.ThrowsAsync<InvalidOperationException>(
+                    async () => await AssertSingleResult<Order>(os => os.Where(o => o.OrderID < 0).Select(o => (int?)o.OrderID).SumAsync()));
+            }
+            finally
+            {
+                AppContext.SetSwitch("Microsoft.EntityFrameworkCore.Issue12314", false);
+            }
+        }
     }
 }

test/EFCore.SqlServer.FunctionalTests/Query/GearsOfWarQuerySqlServerTest.cs

@@ -3037,7 +3037,7 @@ public override void Where_datetimeoffset_now()
             base.Where_datetimeoffset_now();
 
             AssertSql(
-                @"SELECT [m].[Id], [m].[CodeName], [m].[Timeline]
+                @"SELECT [m].[Id], [m].[CodeName], [m].[Rating], [m].[Timeline]
 FROM [Missions] AS [m]
 WHERE [m].[Timeline] <> SYSDATETIMEOFFSET()");
         }
@@ -3047,7 +3047,7 @@ public override void Where_datetimeoffset_utcnow()
             base.Where_datetimeoffset_utcnow();
 
             AssertSql(
-                @"SELECT [m].[Id], [m].[CodeName], [m].[Timeline]
+                @"SELECT [m].[Id], [m].[CodeName], [m].[Rating], [m].[Timeline]
 FROM [Missions] AS [m]
 WHERE [m].[Timeline] <> CAST(SYSUTCDATETIME() AS datetimeoffset)");
         }
@@ -3060,7 +3060,7 @@ public override void Where_datetimeoffset_date_component()
             AssertSql(
                 @"@__Date_0='0001-01-01T00:00:00'
 
-SELECT [m].[Id], [m].[CodeName], [m].[Timeline]
+SELECT [m].[Id], [m].[CodeName], [m].[Rating], [m].[Timeline]
 FROM [Missions] AS [m]
 WHERE CONVERT(date, [m].[Timeline]) > @__Date_0");
         }
@@ -3070,7 +3070,7 @@ public override void Where_datetimeoffset_year_component()
             base.Where_datetimeoffset_year_component();
 
             AssertSql(
-                @"SELECT [m].[Id], [m].[CodeName], [m].[Timeline]
+                @"SELECT [m].[Id], [m].[CodeName], [m].[Rating], [m].[Timeline]
 FROM [Missions] AS [m]
 WHERE DATEPART(year, [m].[Timeline]) = 2");
         }
@@ -3080,7 +3080,7 @@ public override void Where_datetimeoffset_month_component()
             base.Where_datetimeoffset_month_component();
 
             AssertSql(
-                @"SELECT [m].[Id], [m].[CodeName], [m].[Timeline]
+                @"SELECT [m].[Id], [m].[CodeName], [m].[Rating], [m].[Timeline]
 FROM [Missions] AS [m]
 WHERE DATEPART(month, [m].[Timeline]) = 1");
         }
@@ -3090,7 +3090,7 @@ public override void Where_datetimeoffset_dayofyear_component()
             base.Where_datetimeoffset_dayofyear_component();
 
             AssertSql(
-                @"SELECT [m].[Id], [m].[CodeName], [m].[Timeline]
+                @"SELECT [m].[Id], [m].[CodeName], [m].[Rating], [m].[Timeline]
 FROM [Missions] AS [m]
 WHERE DATEPART(dayofyear, [m].[Timeline]) = 2");
         }
@@ -3100,7 +3100,7 @@ public override void Where_datetimeoffset_day_component()
             base.Where_datetimeoffset_day_component();
 
             AssertSql(
-                @"SELECT [m].[Id], [m].[CodeName], [m].[Timeline]
+                @"SELECT [m].[Id], [m].[CodeName], [m].[Rating], [m].[Timeline]
 FROM [Missions] AS [m]
 WHERE DATEPART(day, [m].[Timeline]) = 2");
         }
@@ -3110,7 +3110,7 @@ public override void Where_datetimeoffset_hour_component()
             base.Where_datetimeoffset_hour_component();
 
             AssertSql(
-                @"SELECT [m].[Id], [m].[CodeName], [m].[Timeline]
+                @"SELECT [m].[Id], [m].[CodeName], [m].[Rating], [m].[Timeline]
 FROM [Missions] AS [m]
 WHERE DATEPART(hour, [m].[Timeline]) = 10");
         }
@@ -3120,7 +3120,7 @@ public override void Where_datetimeoffset_minute_component()
             base.Where_datetimeoffset_minute_component();
 
             AssertSql(
-                @"SELECT [m].[Id], [m].[CodeName], [m].[Timeline]
+                @"SELECT [m].[Id], [m].[CodeName], [m].[Rating], [m].[Timeline]
 FROM [Missions] AS [m]
 WHERE DATEPART(minute, [m].[Timeline]) = 0");
         }
@@ -3130,7 +3130,7 @@ public override void Where_datetimeoffset_second_component()
             base.Where_datetimeoffset_second_component();
 
             AssertSql(
-                @"SELECT [m].[Id], [m].[CodeName], [m].[Timeline]
+                @"SELECT [m].[Id], [m].[CodeName], [m].[Rating], [m].[Timeline]
 FROM [Missions] AS [m]
 WHERE DATEPART(second, [m].[Timeline]) = 0");
         }
@@ -3140,7 +3140,7 @@ public override void Where_datetimeoffset_millisecond_component()
             base.Where_datetimeoffset_millisecond_component();
 
             AssertSql(
-                @"SELECT [m].[Id], [m].[CodeName], [m].[Timeline]
+                @"SELECT [m].[Id], [m].[CodeName], [m].[Rating], [m].[Timeline]
 FROM [Missions] AS [m]
 WHERE DATEPART(millisecond, [m].[Timeline]) = 0");
         }