Disable fast path serialization for types with properties using custom converters.

[eiriktsarpalis]

Disables fast path serialization for types with properties using custom converters. While technically it should be possible to support fast path serialization for this scenario, it would require making the JsonPropertyInfo.ConverterBase property public. We should consider doing this in .NET 7.

Fixes #58119.

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Issue Details

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Disables fast path serialization for types with properties using custom converters. While technically it should be possible to support fast path serialization for this scenario, it would require making the JsonPropertyInfo.ConverterBase property public. We should consider doing this in .NET 7.

Fixes #58119.

Author:	eiriktsarpalis
Assignees:	eiriktsarpalis
Labels:	area-System.Text.Json
Milestone:	6.0.0

[eiriktsarpalis]

Should be backported to release/6.0

[steveharter]

While technically it should be possible to support fast path serialization for this scenario, it would require making the JsonPropertyInfo.ConverterBase property public

Why is this? I assume we just need to call myconverter.Write(.

[eiriktsarpalis]

While technically it should be possible to support fast path serialization for this scenario, it would require making the JsonPropertyInfo.ConverterBase property public

Why is this? I assume we just need to call myconverter.Write(.

property-level converters need to be instantiated and cached with property-level metadata (otherwise we would have to allocate a new converter on each serialization). We currently do cache a JsonPropertyInfo[], however the converter property in JsonPropertyInfo has not been made public yet (and therefore cannot be consumed by the fast path serializer). If we wanted to get this working without adding new APIs we would probably need to create a separate JsonConverter[] but that would come at the cost of added allocations and redundant code.

[steveharter]

The long-term and more ideal implementation is to use the property-level converter in the fast-path, meaning add the new serializer-gen interop API (it will need to be public, but treated as internal). If we are going to add any other new interop APIs then I think we should use the converter in the fast path, otherwise I think the PR here is fine.

[steveharter]

At this point, we should disable fast path and use serializer, and fix this in 7.0.

Also this PR needs to get in before the "property factory" support in #58267 is added, since fast path also needs to be disabled for properties that have factory converters.

[steveharter]

/backport to release/6.0

[github-actions]

Started backporting to release/6.0: https://github.com/dotnet/runtime/actions/runs/1195028196