System.Text.Json: [JsonExtensionData] on a property of type JsonObject generates invalid JSON when serializing

[nextdracool]

Description

Invalid JSON is generated when serializing an object when the [JsonExtensionData] attribute is applied to a property of type JsonObject.

Reproduction Steps

see repository: https://github.com/nextdracool/JsonExtensionDataInvalidJsonWithJsonObject

Expected behavior

The JsonObject keys should be added to the serialized JSON object: {"Fixed":0,"foo":"bar"}

Actual behavior

Invalid JSON is generated: {"Fixed":0,{"foo":"bar"}}

Regression?

No response

Known Workarounds

No response

Configuration

.NET 6 RC2,
System.Text.Json 6.0.21.48005

Other information

Possibly related to #60560

This feature was specifically mentioned in Preview 4.

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Issue Details

---

Description

Invalid JSON is generated when serializing an object when the [JsonExtensionData] attribute is applied to a property of type JsonObject.

Reproduction Steps

see repository: https://github.com/nextdracool/JsonExtensionDataInvalidJsonWithJsonObject

Expected behavior

The JsonObject keys should be added to the serialized JSON object: {"Fixed":0,"foo":"bar"}

Actual behavior

Invalid JSON is generated: {"Fixed":0,{"foo":"bar"}}

Regression?

No response

Known Workarounds

No response

Configuration

.NET 6 RC2,
System.Text.Json 6.0.21.48005

Other information

Possibly related to #60560

This feature was specifically mentioned in Preview 4.

Author:	nextdracool
Assignees:	-
Labels:	area-System.Text.Json, untriaged
Milestone:	-

[eiriktsarpalis]

This is caused by the presence of a custom converter for JsonObject, so I believe this is a duplicate of #60560.

@nextdracool please consider upvoting and contributing to the other issue so we can prioritize accordingly.

[nextdracool]

Seems like that's the case. The custom converter is apparently implicitly present even when clearing all converters from the JsonSerializerOptions. There seems to be no way to remove it completely.