Avoid synthetic cache hits in async multi-map

Dapper/SqlMapper.Async.cs

@@ -940,7 +940,7 @@ private static async Task<IEnumerable<TReturn>> MultiMapAsync<TFirst, TSecond, T
                 using var cmd = command.TrySetupAsyncCommand(cnn, info.ParamReader);
                 using var reader = await ExecuteReaderWithFlagsFallbackAsync(cmd, wasClosed, CommandBehavior.SequentialAccess | CommandBehavior.SingleResult, command.CancellationToken).ConfigureAwait(false);
                 if (!command.Buffered) wasClosed = false; // handing back open reader; rely on command-behavior
-                var results = MultiMapImpl<TFirst, TSecond, TThird, TFourth, TFifth, TSixth, TSeventh, TReturn>(null, CommandDefinition.ForCallback(command.Parameters, command.Flags), map, splitOn, reader, identity, true);
+                var results = MultiMapImpl<TFirst, TSecond, TThird, TFourth, TFifth, TSixth, TSeventh, TReturn>(null, CommandDefinition.ForCallback(command.Parameters, command.Flags), map, splitOn, reader, identity, true, info);
                 return command.Buffered ? results.ToList() : results;
             }
             finally
@@ -988,7 +988,7 @@ private static async Task<IEnumerable<TReturn>> MultiMapAsync<TReturn>(this IDbC
                 if (wasClosed) await cnn.TryOpenAsync(command.CancellationToken).ConfigureAwait(false);
                 using var cmd = command.TrySetupAsyncCommand(cnn, info.ParamReader);
                 using var reader = await ExecuteReaderWithFlagsFallbackAsync(cmd, wasClosed, CommandBehavior.SequentialAccess | CommandBehavior.SingleResult, command.CancellationToken).ConfigureAwait(false);
-                var results = MultiMapImpl(null, default, types, map, splitOn, reader, identity, true);
+                var results = MultiMapImpl(null, default, types, map, splitOn, reader, identity, true, info);
                 return command.Buffered ? results.ToList() : results;
             }
             finally

Dapper/SqlMapper.cs

@@ -1584,11 +1584,11 @@ private static IEnumerable<TReturn> MultiMap<TFirst, TSecond, TThird, TFourth, T
             return buffered ? results.ToList() : results;
         }
 
-        private static IEnumerable<TReturn> MultiMapImpl<TFirst, TSecond, TThird, TFourth, TFifth, TSixth, TSeventh, TReturn>(this IDbConnection? cnn, CommandDefinition command, Delegate map, string splitOn, DbDataReader? reader, Identity? identity, bool finalize)
+        private static IEnumerable<TReturn> MultiMapImpl<TFirst, TSecond, TThird, TFourth, TFifth, TSixth, TSeventh, TReturn>(this IDbConnection? cnn, CommandDefinition command, Delegate map, string splitOn, DbDataReader? reader, Identity? identity, bool finalize, CacheInfo? cacheInfo = null)
         {
             object? param = command.Parameters;
             identity ??= new Identity<TFirst, TSecond, TThird, TFourth, TFifth, TSixth, TSeventh>(command.CommandText, command.CommandTypeDirect, cnn!, typeof(TFirst), param?.GetType());
-            CacheInfo cinfo = GetCacheInfo(identity, param, command.AddToCache);
+            CacheInfo cinfo = cacheInfo ?? GetCacheInfo(identity, param, command.AddToCache);
 
             IDbCommand? ownedCommand = null;
             DbDataReader? ownedReader = null;
@@ -1650,7 +1650,7 @@ private static CommandBehavior GetBehavior(bool close, CommandBehavior @default)
             return (close ? (@default | CommandBehavior.CloseConnection) : @default) & Settings.AllowedCommandBehaviors;
         }
 
-        private static IEnumerable<TReturn> MultiMapImpl<TReturn>(this IDbConnection? cnn, CommandDefinition command, Type[] types, Func<object[], TReturn> map, string splitOn, DbDataReader? reader, Identity? identity, bool finalize)
+        private static IEnumerable<TReturn> MultiMapImpl<TReturn>(this IDbConnection? cnn, CommandDefinition command, Type[] types, Func<object[], TReturn> map, string splitOn, DbDataReader? reader, Identity? identity, bool finalize, CacheInfo? cacheInfo = null)
         {
             if (types.Length < 1)
             {
@@ -1659,7 +1659,7 @@ private static IEnumerable<TReturn> MultiMapImpl<TReturn>(this IDbConnection? cn
 
             object? param = command.Parameters;
             identity ??= new IdentityWithTypes(command.CommandText, command.CommandTypeDirect, cnn!, types[0], param?.GetType(), types);
-            CacheInfo cinfo = GetCacheInfo(identity, param, command.AddToCache);
+            CacheInfo cinfo = cacheInfo ?? GetCacheInfo(identity, param, command.AddToCache);
 
             IDbCommand? ownedCommand = null;
             DbDataReader? ownedReader = null;

Directory.Packages.props

@@ -38,6 +38,7 @@
     <PackageVersion Include="RepoDb.SqlServer" Version="1.13.1" />
     <PackageVersion Include="ServiceStack.OrmLite.SqlServer" Version="10.0.6" />
     <PackageVersion Include="Snowflake.Data" Version="5.5.0" />
+    <PackageVersion Include="pengdows.crud.fakeDb" Version="2.0.5" />
     <PackageVersion Include="SqlMarshal" Version="0.5.0" />
     <PackageVersion Include="SubSonic" Version="3.0.0.4" />
     <PackageVersion Include="Susanoo.SqlServer" Version="1.2.4.2" />

tests/Dapper.Tests/Dapper.Tests.csproj

@@ -32,6 +32,7 @@
   </ItemGroup>
 
   <ItemGroup Condition="'$(TargetFramework)' != 'net481'">
+    <PackageReference Include="pengdows.crud.fakeDb" />
     <PackageReference Include="Npgsql" />
     <PackageReference Include="Snowflake.Data" />
   </ItemGroup>

tests/Dapper.Tests/FakeDbTests.Issue2240.cs

@@ -0,0 +1,42 @@
+#if !NET481
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+using pengdows.crud.fakeDb;
+using Xunit;
+
+namespace Dapper.Tests;
+
+public sealed class FakeDbIssue2240Tests
+{
+    [Fact]
+    public async Task FirstAsyncMultiMapExecutionDoesNotRecordSyntheticCacheHit()
+    {
+        SqlMapper.PurgeQueryCache();
+        using var connection = new fakeDbConnection(new FakeDataStore());
+        connection.EnqueueReaderResult(new[]
+        {
+            new Dictionary<string, object?>
+            {
+                ["A"] = 1,
+                ["B"] = 2,
+                ["C"] = 3,
+            },
+        });
+        connection.Open();
+
+        await connection.QueryAsync<First, Second, Third, int>(
+            "select 1 as A, 2 as B, 3 as C",
+            (a, b, c) => a.A + b.B + c.C,
+            splitOn: "B,C");
+
+        var cached = SqlMapper.GetCachedSQL().ToList();
+        Assert.NotEmpty(cached);
+        Assert.Equal(0, cached.Single().Item3);
+    }
+
+    private sealed class First { public int A { get; set; } }
+    private sealed class Second { public int B { get; set; } }
+    private sealed class Third { public int C { get; set; } }
+}
+#endif