Error when using $defer with incrementalSpec=v0.1

Product

Hot Chocolate

Version

16.6.3

Link to minimal reproduction

https://github.com/srollinet/HotChocolate.IncrementalResultFormatAdapters.BugMinimalRepro

Steps to reproduce

1. Start the server
2. In Nitro, set header Accept with value application/json, multipart/mixed; incrementalSpec=v0.1
3. Execute the following query:

query {
  products {
    nodes {
      id
      ...ProductItemFragment @defer(label: "ProductsQuery$defer$productDetails")
    }
  }
}

fragment ProductItemFragment on Product {
  productNumber
}

What is expected?

Query works, like in version 15

{
  "data": {
    "products": {
      "nodes": [
        {
          "id": "1",
          "productNumber": 1001
        },
        {
          "id": "2",
          "productNumber": 1002
        },
        {
          "id": "3",
          "productNumber": 1003
        }
      ]
    }
  }
}

What is actually happening?

Sometimes, the result is empty, sometimes it's partial.

When receiving a partial result, patch1 is ok

{
  "data": {
    "products": {
      "nodes": [
        {
          "id": "1"
        },
        {
          "id": "2"
        },
        {
          "id": "3"
        }
      ]
    }
  }
}

Then patch2 fails

{
  "name": "ServerParseError",
  "statusCode": 200,
  "statusText": "OK",
  "bodyText": ""
}

Relevant log output

fail: Microsoft.AspNetCore.Server.Kestrel[13]
      Connection id "0HNO9ONKK0TT6", Request id "0HNO9ONKK0TT6:00000002": An unhandled exception was thrown by the application.
      System.InvalidOperationException: The requested operation requires an element of type 'Object', but the target element has type 'Array'.
         at System.Text.Json.ThrowHelper.ThrowJsonElementWrongTypeException(JsonTokenType expectedType, JsonTokenType actualType)
         at System.Text.Json.JsonDocument.TryGetNamedPropertyValue(Int32 index, ReadOnlySpan`1 propertyName, JsonElement& value)
         at System.Text.Json.JsonElement.TryGetProperty(String propertyName, JsonElement& value)
         at HotChocolate.Transport.Formatters.IncrementalRfc1ResultFormatAdapter.WriteMergedObject(JsonWriter writer, OperationResultFormatterContext context, Path path, JsonElement patchObject, DeferSelectionTree selection)
         at HotChocolate.Transport.Formatters.IncrementalRfc1ResultFormatAdapter.TryCreateMergedData(OperationResultFormatterContext context, Path pendingPath, Path path, String label, JsonDocument patchDocument, ReadOnlyMemorySegment& mergedData, Path& mergedPath)
         at HotChocolate.Transport.Formatters.IncrementalRfc1ResultFormatAdapter.WriteIncremental(JsonWriter writer, OperationResult result, JsonSerializerOptions options, OperationResultFormatterContext context)
         at HotChocolate.Transport.Formatters.JsonResultFormatter.Format(OperationResult result, JsonWriter writer, Boolean useIncrementalRfc1, OperationResultFormatterContext& context)
         at HotChocolate.Transport.Formatters.JsonResultFormatter.FormatInternal(OperationResult result, IBufferWriter`1 bufferWriter, Boolean useIncrementalRfc1, OperationResultFormatterContext& context)
         at HotChocolate.Transport.Formatters.JsonResultFormatter.Format(OperationResult result, IBufferWriter`1 writer, Boolean useIncrementalRfc1, OperationResultFormatterContext& context)
         at HotChocolate.Transport.Formatters.MultiPartResultFormatter.MessageHelper.WritePayload(IBufferWriter`1 writer, OperationResult result, JsonResultFormatter payloadFormatter, Boolean useIncrementalRfc1, OperationResultFormatterContext& context)
         at HotChocolate.Transport.Formatters.MultiPartResultFormatter.FormatResponseStreamAsync(IResponseStream responseStream, PipeWriter writer, Boolean useIncrementalRfc1, CancellationToken ct)
         at HotChocolate.Transport.Formatters.MultiPartResultFormatter.FormatResponseStreamAsync(IResponseStream responseStream, PipeWriter writer, Boolean useIncrementalRfc1, CancellationToken ct)
         at HotChocolate.Transport.Formatters.MultiPartResultFormatter.FormatResponseStreamAsync(IResponseStream responseStream, PipeWriter writer, Boolean useIncrementalRfc1, CancellationToken ct)
         at HotChocolate.AspNetCore.Formatters.DefaultHttpResponseFormatter.FormatInternalAsync(HttpResponse response, IExecutionResult result, Nullable`1 proposedStatusCode, FormatInfo format, AcceptMediaType acceptMediaType, CancellationToken cancellationToken)
         at HotChocolate.AspNetCore.Formatters.DefaultHttpResponseFormatter.FormatAsync(HttpResponse response, IExecutionResult result, AcceptMediaType[] acceptMediaTypes, Nullable`1 proposedStatusCode, CancellationToken cancellationToken)
         at HotChocolate.AspNetCore.HttpPostMiddlewareBase.HandleRequestAsync(HttpContext context, ExecutorSession session, CancellationToken ct)
         at HotChocolate.AspNetCore.HttpPostMiddlewareBase.HandleRequestAsync(HttpContext context, ExecutorSession session, CancellationToken ct)
         at HotChocolate.AspNetCore.HttpPostMiddlewareBase.InvokeAsync(HttpContext context)
         at HotChocolate.AspNetCore.MiddlewareFactory.<>c__DisplayClass0_0.<<CreateCancellationMiddleware>b__1>d.MoveNext()
      --- End of stack trace from previous location ---
         at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddlewareImpl.Invoke(HttpContext context)
         at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddlewareImpl.Invoke(HttpContext context)
         at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.HttpProtocol.ProcessRequests[TContext](IHttpApplication`1 application)

Additional context

In my quick analysis, the problem happens in IncrementalRfc1ResultFormatAdapter.TryCreateMergedData https://github.com/ChilliCream/graphql-platform/blob/7ce54d90aaa724519fa10680408e788717154fab/src/HotChocolate/AspNetCore/src/Transport.Formatters/IncrementalResultFormatAdapters.cs#L213-L215

relativePath has value [0]. So, in WriteWrappedPatch, patch is wrapped in an array

https://github.com/ChilliCream/graphql-platform/blob/7ce54d90aaa724519fa10680408e788717154fab/src/HotChocolate/AspNetCore/src/Transport.Formatters/IncrementalResultFormatAdapters.cs#L156-L167

And later, in WriteMergedObject, TryGetProperty throws because patchObject is an array
https://github.com/ChilliCream/graphql-platform/blob/7ce54d90aaa724519fa10680408e788717154fab/src/HotChocolate/AspNetCore/src/Transport.Formatters/IncrementalResultFormatAdapters.cs#L386-L390