Update JsonObjectTypeExtensions.cs

[vickytr44]

Root cause: When GetDateTimeOffset() is performed on null, we will get an error stating "The requested operation requires an element of type 'String', but the target element has type 'Null' ". This will happen when the value of DateTime field is null.

Code fix: The proposed change will ensure that the system returns null when DateTime field is null instead of throwing an error.

[CLAassistant]

All committers have signed the CLA.

[michaelstaib]

Can you provide a minimal test showing the issue you are referring to? I have the feeling that this does not really fix the the issue or rather applies some logic that overlays an issue here.

[michaelstaib]

@vickytr44 do you want to advance this PR?

[vickytr44]

Yes, I would like to move forward with the pull request. Let me also create a sample project where we can reproduce this issue.

[vickytr44]

I have created a sample project to reproduce the issue. I've included the link for the project.
GraphQl_IntegratingRestService

Here Book type will get its Author details from a rest service and for one of the author the birthdate is null . When you try to query the author's details the query will throw an error.
Note: Here the DateTime is nullable.

Query:
{ bookById(id:4){ title id author{ id name birthdate } } }

Result:
{ "errors": [ { "message": "Unexpected Execution Error", "locations": [ { "line": 8, "column": 7 } ], "path": [ "bookById", "author", "birthdate" ], "extensions": { "message": "The requested operation requires an element of type 'String', but the target element has type 'Null'.", "stackTrace": " at System.Text.Json.JsonDocument.TryGetValue(Int32 index, DateTimeOffset& value)\r\n at HotChocolate.Types.JsonObjectTypeExtensions.<>c__DisplayClass2_0.<InferResolver>b__12(IPureResolverContext ctx)\r\n at HotChocolate.Execution.Processing.Tasks.ResolverTaskFactory.ResolveAndCompleteInline(OperationContext operationContext, MiddlewareContext resolverContext, ISelection selection, Path path, Int32 responseIndex, ObjectType parentType, Object parent, ObjectResult parentResult, List1 bufferedTasks)"
}
}
],
"data": {
"bookById": {
"title": "Pro WPF: Windows Presentation Foundation in .NET 3.0",
"id": 4,
"author": {
"id": 3,
"name": "Matthew MacDonald",
"birthdate": null
}
}
}
}
`