Preserve string parameter size set by type handlers

Dapper/SqlMapper.cs

@@ -2859,7 +2859,7 @@ private static bool IsValueTuple(Type? type) => (type?.IsValueType == true
                     il.EmitCall(OpCodes.Callvirt, typeof(IDataParameter).GetProperty(nameof(IDataParameter.Value))!.GetSetMethod()!, null);// stack is now [parameters] [[parameters]] [parameter]
                 }
 
-                if (prop.PropertyType == typeof(string))
+                if (prop.PropertyType == typeof(string) && handler is null)
                 {
                     var endOfSize = il.DefineLabel();
                     var sizeLocal = GetSizeLocal();

Directory.Packages.props

@@ -35,6 +35,7 @@
     <PackageVersion Include="Norm.net" Version="5.4.0" />
     <PackageVersion Include="Npgsql" Version="10.0.2" />
     <PackageVersion Include="PetaPoco" Version="5.1.306" />
+    <PackageVersion Include="pengdows.crud.fakeDb" Version="2.0.5" />
     <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" />

tests/Dapper.Tests/Dapper.Tests.csproj

@@ -31,8 +31,9 @@
     <PackageReference Include="log4net" />
   </ItemGroup>
 
-  <ItemGroup Condition="'$(TargetFramework)' != 'net481'">
-    <PackageReference Include="Npgsql" />
+  <ItemGroup Condition="'$(TargetFramework)' != 'net481'">
+    <PackageReference Include="pengdows.crud.fakeDb" />
+    <PackageReference Include="Npgsql" />
     <PackageReference Include="Snowflake.Data" />
   </ItemGroup>
 

tests/Dapper.Tests/FakeDbTests.Issue2141.cs

@@ -0,0 +1,49 @@
+#if !NET481
+using System.Data;
+using pengdows.crud.fakeDb;
+using Xunit;
+
+namespace Dapper.Tests
+{
+    public sealed class FakeDbIssue2141Tests
+    {
+        [Fact]
+        public void StringTypeHandlerOwnsParameterSize()
+        {
+            SqlMapper.RemoveTypeMap(typeof(string));
+            var handler = new SizedStringHandler();
+            SqlMapper.AddTypeHandler(handler);
+            try
+            {
+                using var conn = new fakeDbConnection(new FakeDataStore());
+                conn.EnqueueNonQueryResult(1);
+                conn.Open();
+
+                conn.Execute("select @value", new { value = "hello" });
+
+                Assert.Equal(7, handler.LastParameter!.Size);
+            }
+            finally
+            {
+                SqlMapper.ResetTypeHandlers();
+                SqlMapper.AddTypeMap(typeof(string), DbType.String);
+            }
+        }
+
+        private sealed class SizedStringHandler : SqlMapper.TypeHandler<string>
+        {
+            public IDbDataParameter? LastParameter { get; private set; }
+
+            public override string Parse(object value) => (string)value;
+
+            public override void SetValue(IDbDataParameter parameter, string? value)
+            {
+                LastParameter = parameter;
+                parameter.DbType = DbType.String;
+                parameter.Value = value;
+                parameter.Size = 7;
+            }
+        }
+    }
+}
+#endif