fix projection of __typename v10

src/Core/Types.Selection.Abstractions.Tests/SelectionTestsBase.cs

@@ -116,6 +116,52 @@ public virtual void Execute_Selection_Scalar()
                 });
         }
 
+        [Fact]
+        public virtual void Execute_Selection_SingleScalarAndTypeName()
+        {
+            // arrange
+            IServiceCollection services;
+            Func<IResolverContext, IEnumerable<Foo>> resolver;
+            (services, resolver) = _provider.CreateResolver(SAMPLE);
+
+            IQueryable<Foo> resultCtx = null;
+            ISchema schema = SchemaBuilder.New()
+                .AddServices(services.BuildServiceProvider())
+                .AddQueryType<Query>(
+                    d => d.Field(t => t.Foos)
+                        .Resolver(resolver)
+                        .Use(next => async ctx =>
+                        {
+                            await next(ctx).ConfigureAwait(false);
+                            resultCtx = ctx.Result as IQueryable<Foo>;
+                        })
+                        .UseSelection())
+                .Create();
+            IQueryExecutor executor = schema.MakeExecutable();
+
+            // act
+            executor.Execute(
+                "{ foos { bar __typename } }");
+
+            // assert
+            Assert.NotNull(resultCtx);
+            Assert.Collection(resultCtx.ToArray(),
+                x =>
+                {
+                    Assert.Equal("aa", x.Bar);
+                    Assert.Equal(0, x.Baz);
+                    Assert.Null(x.Nested);
+                    Assert.Null(x.ObjectArray);
+                },
+                x =>
+                {
+                    Assert.Equal("bb", x.Bar);
+                    Assert.Equal(0, x.Baz);
+                    Assert.Null(x.Nested);
+                    Assert.Null(x.ObjectArray);
+                });
+        }
+
         [Fact]
         public virtual void Execute_Selection_MultipleScalar()
         {
@@ -1522,7 +1568,7 @@ public class Foo
 
             public string GetComputedField() => Bar + Baz;
 
-            public string GetComputedFieldParent([Parent]Foo foo) => foo.Bar + foo.Baz;
+            public string GetComputedFieldParent([Parent] Foo foo) => foo.Bar + foo.Baz;
 
             public static Foo Create(string bar, int baz)
             {

src/Core/Types.Selection/SelectionVisitor.cs

@@ -5,6 +5,7 @@
 using HotChocolate.Execution;
 using HotChocolate.Language;
 using HotChocolate.Resolvers;
+using HotChocolate.Types.Introspection;
 using HotChocolate.Types.Selections.Handlers;
 using HotChocolate.Utilities;
 
@@ -40,6 +41,15 @@ public Expression<Func<T, T>> Project<T>()
             return (Expression<Func<T, T>>)Closures.Peek().CreateMemberInitLambda();
         }
 
+        protected override bool EnterLeaf(IFieldSelection selection)
+        {
+            if (IntrospectionFields.TypeName.Equals(selection.Field.Name))
+            {
+                return false;
+            }
+            return base.EnterLeaf(selection);
+        }
+
         protected override void LeaveLeaf(IFieldSelection selection)
         {
             if (selection.Field.Member is PropertyInfo member)

src/Core/Types.Selection/SelectionVisitorBase.cs

@@ -5,6 +5,7 @@
 using HotChocolate.Execution;
 using HotChocolate.Language;
 using HotChocolate.Resolvers;
+using HotChocolate.Types.Introspection;
 using HotChocolate.Types.Relay;
 using static HotChocolate.Utilities.DotNetTypeInfoFactory;
 
@@ -236,7 +237,8 @@ private static bool HasNonProjectableField(IReadOnlyList<IFieldSelection> select
         {
             for (int i = 0; i < selections.Count; i++)
             {
-                if (!(selections[i].Field.Member is PropertyInfo))
+                if (!(selections[i].Field.Member is PropertyInfo) &&
+                    !IntrospectionFields.TypeName.Equals(selections[i].Field.Name))
                 {
                     return true;
                 }