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JsonSerializer.Serialize produces invalid JSON for [JsonExtensionData] property #97225
Description
Description
When serializing object containing property marked with [JsonExtensionData] attribute, serializer produces invalid JSON like this one: {"Id":1,{"nested":true}}
Reproduction Steps
Run the following code
var mix = new Mix
{
Id = 1,
Extra = new() { ["nested"] = true, }
};
var text = System.Text.Json.JsonSerializer.Serialize(mix);
Console.WriteLine(text);
// output {"Id":1,{"nested":true}}
public class Mix
{
public int Id { get; set; }
[System.Text.Json.Serialization.JsonExtensionData]
public System.Text.Json.Nodes.JsonObject? Extra { get; set; }
}Expected behavior
Correct JSON like {"Id":1,"nested":true} or at least valid JSON as if there was not [JsonExtensionData] attribute ({"Id":1,"Extra":{"nested":true}} ).
Actual behavior
Invalid JSON {"Id":1,{"nested":true}}
Regression?
Reproducible at least on .Net 6 to .Net 8
Known Workarounds
No response
Configuration
.Net 8
Windows 11
x64
Other information
No response
Activity
eiriktsarpalis commentedon Jan 19, 2024
Can confirm that this occurs. It seems we never added testing for the serialization scenario -- deserialization appears to be working as expected.
elgonzo commentedon Jan 19, 2024
There is a related question as to whether this scenario is supposed to be allowed or not. Because the documentation for JsonExtensionDataAttribute states:
However, the example code in the report uses
JsonObjectas extension data property - anIDictionary<string, JsonNode>, which according to the JsonExtensionDataAttribute documentation is not an allowed dictionary type.So, basically the problem is either
IDictionary<string, JsonNode>is supposed to be supported as extension data property type, in which case there is both a bug in the implementation and an error in theJsonExtensionDataAttributedocumentation.@eiriktsarpalis
Does this then mean the documentation for JsonExtensionDataAttribute is wrong about the types allowed for extension data properties?
eiriktsarpalis commentedon Jan 19, 2024
The documentation is correctly stating that
JsonObjectis one of the supported types. However there is a bug specifically impacting serialization for the particular type (FWIWJsonExtensionDatais a feature primarily oriented towards dserialization).elgonzo commentedon Jan 19, 2024
You seem to be mistaken. Where does the documentation for JsonExtensionDataAttribute state this?
The related documentation page "How to handle overflow JSON or use JsonElement or JsonNode in System.Text.Json" also does not support your claim:
eiriktsarpalis commentedon Jan 19, 2024
You're right, I misread the documentation which appears to be out of date. The correct statement on supported types can actually be found in the error messages of the implementation itself:
runtime/src/libraries/System.Text.Json/gen/Resources/Strings.resx
Lines 150 to 152 in 2d751ca
In other words, what I mentioned earlier holds.
JsonObjectis supported and there is a bug specifically concerning serialization.elgonzo commentedon Jan 19, 2024
Okay. Regarding the documentation being out of date, should i file an issue report with the docs repo, or do you handle this internally between teams?
eiriktsarpalis commentedon Jan 19, 2024
It would help if you could file a separate issue in dotnet-api-docs. Thanks!
RutulPatel8 commentedon Jan 20, 2024
Yes I have tested with Dot net core 6 version.
It is reproducible.
TheArcaneBrony commentedon Mar 23, 2025
Still reproducible in dotnet 9
Fix JsonSerializer.Serialize producing invalid JSON for [JsonExtensio…