Fixed issue with errors in mutation convention when explicitly bindun… (

#7548)

src/HotChocolate/Core/src/Types.Errors/ErrorObjectType.cs

@@ -6,6 +6,7 @@ protected override void Configure(IObjectTypeDescriptor<T> descriptor)
     {
         descriptor.Extend().OnBeforeCreate(RewriteMessageFieldToNonNullableStringType);
         descriptor.Extend().Definition.ContextData.MarkAsError();
+        descriptor.BindFieldsImplicitly();
     }
 
     private void RewriteMessageFieldToNonNullableStringType(

src/HotChocolate/Core/src/Types.Errors/ExceptionObjectType.cs

@@ -15,6 +15,7 @@ protected override void Configure(IObjectTypeDescriptor<T> descriptor)
         descriptor.Ignore(x => x.GetBaseException());
         descriptor.Field(x => x.Message).Type<NonNullType<StringType>>();
         descriptor.Extend().Definition.ContextData.MarkAsError();
+        descriptor.BindFieldsImplicitly();
     }
 
     private static string GetNameFromException()

src/HotChocolate/Core/test/Types.Mutations.Tests/AnnotationBasedMutations.cs

@@ -1275,6 +1275,31 @@ public async Task Mutation_With_ErrorAnnotatedAndCustomInterface_LateAndEarlyReg
         result.Print().MatchSnapshot();
     }
 
+    [Fact]
+    public async Task InferErrorEvenIfExplicitFieldBindingIsUsed()
+    {
+        var schema =
+            await new ServiceCollection()
+                .AddGraphQL()
+                .AddQueryType(d => d.Field("abc").Resolve("def"))
+                .AddMutationType<ExplicitMutation>(c => c.Field(t => t.DoSomething(default)))
+                .AddMutationConventions()
+                .BuildSchemaAsync();
+
+        schema.Print().MatchSnapshot();
+    }
+
+    public class ExplicitMutation
+    {
+        public FieldResult<int, ExplicitCustomError> DoSomething(int status)
+            => new ExplicitCustomError { Message = "Error" };
+    }
+
+    public sealed class ExplicitCustomError
+    {
+        public required string Message { get; set; }
+    }
+
     public class SimpleMutation
     {
         public string DoSomething(string something)

src/HotChocolate/Core/test/Types.Mutations.Tests/__snapshots__/AnnotationBasedMutations.InferErrorEvenIfExplicitFieldBindingIsUsed.snap

@@ -0,0 +1,31 @@
+schema {
+  query: Query
+  mutation: ExplicitMutation
+}
+
+interface Error {
+  message: String!
+}
+
+type DoSomethingPayload {
+  int: Int
+  errors: [DoSomethingError!]
+}
+
+type ExplicitCustomError implements Error {
+  message: String!
+}
+
+type ExplicitMutation {
+  doSomething(input: DoSomethingInput!): DoSomethingPayload!
+}
+
+type Query {
+  abc: String
+}
+
+union DoSomethingError = ExplicitCustomError
+
+input DoSomethingInput {
+  status: Int!
+}