JsonElement should map to `JsonType` not `JsonType!`

[onionhammer]

Is there an existing issue for this?

• [X] I have searched the existing issues

Product

Hot Chocolate

Describe the bug

JsonElement and other types that utilize it allow for null values on the .NET side;

for example:

using System.Text.Json;

var elem = JsonSerializer.Deserialize<JsonElement>("null");
elem // elem is NOT null, its `ValueKind` is `Null`

However, in HotChocolate by default, JsonElement becomes a non-null JsonType scalar.

using System.Text.Json;
using System.Text.Json.Serialization;

namespace Test;

[MutationType]
public class TestMutation
{
    public MyInputType TakeFlexibleInput(MyInputType test)
    {
        return test;
    }
}

public class MyInputType
{
    [JsonExtensionData]
    public Dictionary<string, JsonElement>? ExtensionData { get; set; }
}

yields a schema like

type Mutation {
  takeFlexibleInput(input: TakeFlexibleInputInput!): TakeFlexibleInputPayload!
}

type MyInputType {
  extensionData: [KeyValuePairOfStringAndJsonElement!]
}

input KeyValuePairOfStringAndJsonElementInput {
  key: String!
  value: JSON!
}

Which does not allow for null values within the extension data, meaning any valid null JSON value will turn into a hot chocolate validation error.

Steps to reproduce

1. Utilize above code
2. Post a mutation with a null in the list of values, i.e. { "myField": null }

Relevant log output

No response

Additional Context?

Other things I tried:

1. Decorating ExtensionData with JsonElement? fails because .NET's JsonSerializer doesnt accept that, it gives: "".ExtensionData' is invalid. It must implement 'IDictionary<string, JsonElement>' or 'IDictionary<string, object>', or be 'JsonObject'.""

2. .BindRuntimeType<IDictionary<string, JsonElement>, JsonType>() gives an array of non-null JSON values, which will not serialize well to a dictionary, also it is still non-null only

Workaround:

Perhaps create a custom json 'dictionary' scalar?

Version

13.5.1

[glen-84]

I'm not able to reproduce this issue if I change Dictionary<string, JsonElement>? to Dictionary<string, JsonElement?>? and post the following mutation:

mutation {
  takeFlexibleInput(test: { extensionData: [{ key: "x", value: null }] }) {
    extensionData {
      key
      value
    }
  }
}

Am I missing something?

[onionhammer]

@glen-84 JsonElement can represent null JSON as a valid value, so just because JsonElement is NOT null, doesnt mean that the JSON is NOT null.

In other words, Dictionary<string, JsonElement> (non-null JsonElement) should have no trouble binding to { key: "x", value: null }; null would just be the equivalent of a JsonElement with ValueKind of Null

[michaelstaib]

There is no map semantic in GraphQL ... the dictionary is just a list to Hot Chocolate. Also I would not expose dictionaries like that... rather expose the map itself as JsonType and get a cleaner schema. I am closing this issue.

[onionhammer]

@michaelstaib it's not me that's choosing JsonExtensionData as a dictionary. Not sure if I understand your explanation... also the whole dictionary/list/map thing is completely besides the point; the point is that a non-null JsonElement can result a null value on the client. If you declare it not null by giving it a bang(!) you're essentially lying to the typescript compiler