.NET 8.0 JsonArray.Add throws System.InvalidOperationException: "The element cannot be an object or array."

[campersau]

Description

Adding a JsonElement via JsonArray.Add throws an exception with .NET 8. In .NET 7 it worked without throwing.

It is interesting that JsonArray.Add worked in .NET 7 but JsonValue.Create fails in both .NET 7/8 when passing in a JsonElement with ValueKind.Object/Array.

Related: #70427
Regression in 1db4357 ?

Reproduction Steps

using System.Text.Json;
using System.Text.Json.Nodes;

var element = JsonDocument.Parse("""{"test":"hello world"}""");

var array = new JsonArray();
array.Add(element.RootElement); // .NET 8.0 throws here

Console.WriteLine(array.ToJsonString());

Expected behavior

Works without exception.

Actual behavior

Throws a System.InvalidOperationException: "The element cannot be an object or array."

   bei System.Text.Json.ThrowHelper.ThrowInvalidOperationException_NodeElementCannotBeObjectOrArray()
   bei System.Text.Json.Nodes.JsonValue.VerifyJsonElementIsNotArrayOrObject(JsonElement& element)
   bei System.Text.Json.Nodes.JsonValue.Create[T](T value, Nullable`1 options)
   bei System.Text.Json.Nodes.JsonArray.Add[T](T value)

Regression?

Yes, it works with .NET 7.0

Known Workarounds

For this particular case the JsonDocument could be added instead of the RootElement.
A general workaround would be #70427 (comment)

Configuration

.NET 8
Windows
x64

Other information

No response

Tagging subscribers to this area: @dotnet/area-system-text-json, @gregsdennis
See info in area-owners.md if you want to be subscribed.

Issue Details

---

Description

Adding a JsonElement via JsonArray.Add throws an exception with .NET 8. In .NET 7 it worked without throwing.

It is interesting that JsonArray.Add worked in .NET 7 but JsonValue.Create fails in both .NET 7/8 when passing in a JsonElement with ValueKind.Object/Array.

Related: #70427
Regression in 1db4357 ?

Reproduction Steps

using System.Text.Json;
using System.Text.Json.Nodes;

var element = JsonDocument.Parse("""{"test":"hello world"}""");

var array = new JsonArray();
array.Add(element.RootElement); // .NET 8.0 throws here

Console.WriteLine(array.ToJsonString());

Expected behavior

Works without exception.

Actual behavior

Throws a System.InvalidOperationException: "The element cannot be an object or array."

   bei System.Text.Json.ThrowHelper.ThrowInvalidOperationException_NodeElementCannotBeObjectOrArray()
   bei System.Text.Json.Nodes.JsonValue.VerifyJsonElementIsNotArrayOrObject(JsonElement& element)
   bei System.Text.Json.Nodes.JsonValue.Create[T](T value, Nullable`1 options)
   bei System.Text.Json.Nodes.JsonArray.Add[T](T value)

Regression?

Yes, it works with .NET 7.0

Known Workarounds

For this particular case the JsonDocument could be added instead of the RootElement.
A general workaround would be #70427 (comment)

Configuration

.NET 8
Windows
x64

Other information

No response

Author:	campersau
Assignees:	-
Labels:	area-System.Text.Json
Milestone:	-

[eiriktsarpalis]

It seems that the particular example was working until .NET 7 because the method was creating a JsonValue instance directly:

runtime/src/libraries/System.Text.Json/src/System/Text/Json/Nodes/JsonArray.cs

Line 111 in 90f1525

JsonNode jNode = value as JsonNode ?? new JsonValueNotTrimmable<T>(value);

Bypassing the usual validation in place when creating JsonValue instances from JsonElement:

runtime/src/libraries/System.Text.Json/src/System/Text/Json/Nodes/JsonValue.CreateOverloads.cs

Line 319 in 90f1525

VerifyJsonElementIsNotArrayOrObject(ref element);

The validation is in place because JsonValue instances do not support nesting, so if you try to pass in anything more complex that won't be inspectible by the DOM APIs (although it would still generated valid JSON).

Nevertheless, we should try to fix this because it's a regression. I'll follow up with a PR that both fixes the problem and ensures JsonElements are mapped to the correct JsonNode representation.