System.Text.Json ObjectConverter does not handle reference metadata correctly on deserialization

[eiriktsarpalis]

The following test fails with both JsonElement and JsonNode type handling.

        [Theory]
        [InlineData(JsonUnknownTypeHandling.JsonElement)]
        [InlineData(JsonUnknownTypeHandling.JsonNode)]
        public void ObjectConverterShouldHandleReferenceMetadata(JsonUnknownTypeHandling typehandling)
        {
            var options = new JsonSerializerOptions { ReferenceHandler = ReferenceHandler.Preserve, UnknownTypeHandling = typehandling };
            string json = @"[{ ""$id"" : ""1"" },{ ""$ref"" : ""1""}]";
            object[] deserialized = JsonSerializer.Deserialize<object[]>(json, options);
            Assert.Same(deserialized[0], deserialized[1]);
        }

We need to update the TryGetReferenceFromJsonElement method in ObjectConverter:

runtime/src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Converters/Object/ObjectConverter.cs

Lines 43 to 48 in f8d5706

	// Edge case where we want to lookup for a reference when parsing into typeof(object)
	if (options.ReferenceHandlingStrategy == ReferenceHandlingStrategy.Preserve &&
	JsonSerializer.TryGetReferenceFromJsonElement(ref state, element, out object? referenceValue))
	{
	value = referenceValue;
	}

so that it handles both $id and $ref metadata. We also need to expose equivalent functionality for JsonNode, which currently is not implemented.

cc @jozkee @steveharter

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Issue Details

---

The following test fails with both JsonElement and JsonNode type handling.

        [Theory]
        [InlineData(JsonUnknownTypeHandling.JsonElement)]
        [InlineData(JsonUnknownTypeHandling.JsonNode)]
        public void ObjectConverterShouldHandleReferenceMetadata(JsonUnknownTypeHandling typehandling)
        {
            var options = new JsonSerializerOptions { ReferenceHandler = ReferenceHandler.Preserve, UnknownTypeHandling = typehandling };
            string json = @"[{ ""$id"" : ""1"" },{ ""$ref"" : ""1""}]";
            object[] deserialized = JsonSerializer.Deserialize<object[]>(json, options);
            Assert.Same(deserialized[0], deserialized[1]);
        }

We need to update the TryGetReferenceFromJsonElement method in ObjectConverter:

runtime/src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Converters/Object/ObjectConverter.cs

Lines 43 to 48 in f8d5706

	// Edge case where we want to lookup for a reference when parsing into typeof(object)
	if (options.ReferenceHandlingStrategy == ReferenceHandlingStrategy.Preserve &&
	JsonSerializer.TryGetReferenceFromJsonElement(ref state, element, out object? referenceValue))
	{
	value = referenceValue;
	}

so that it handles both $id and $ref metadata. We also need to expose equivalent functionality for JsonNode, which currently is not implemented.

cc @jozkee @steveharter

Author:	eiriktsarpalis
Assignees:	-
Labels:	area-System.Text.Json, untriaged
Milestone:	7.0.0