Async and sync boxed serialize differ in behaviour (System.Text.Json) #31464
Description
private static JsonSerializerOptions _jsonSerializerOptions = new JsonSerializerOptions { WriteIndented = false };
static async Task<int> Main(string[] args)
{
var empty = new {};
var valued = new {x = 1, y = true};
Console.WriteLine("Generic");
await Write(empty);
await Write(valued);
Console.WriteLine("Boxed");
await BoxedWrite(empty);
await BoxedWrite(valued);
return 0;
}
private static async Task Write<T>(T x)
{
var blocking = Serialize(x);
var async = await SerializeAsync(x);
Console.WriteLine("-- blocking --");
Console.WriteLine(blocking);
Console.WriteLine("-- async --");
Console.WriteLine(async);
}
private static async Task BoxedWrite(object x)
{
var blocking = Serialize(x);
var async = await SerializeAsync(x);
Console.WriteLine("-- blocking --");
Console.WriteLine(blocking);
Console.WriteLine("-- async --");
Console.WriteLine(async);
}
private static string Serialize<T>(T data)
{
using var stream = new MemoryStream();
using var writer = new Utf8JsonWriter(stream);
JsonSerializer.Serialize<T>(writer, data, _jsonSerializerOptions);
return Encoding.UTF8.GetString(stream.ToArray());
}
private static async Task<string> SerializeAsync<T>(T data)
{
using var stream = new MemoryStream();
await JsonSerializer.SerializeAsync<T>(stream, data, _jsonSerializerOptions, default);
return Encoding.UTF8.GetString(stream.ToArray());
}emits:
Generic
-- blocking --
{}
-- async --
{}
-- blocking --
{"x":1,"y":true}
-- async --
{"x":1,"y":true}
Boxed
-- blocking --
{}
-- async --
{}
-- blocking --
{"x":1,"y":true}
-- async --
{} int maxPropertyIndex = JsonClassInfo.PropertyCacheArray.Length;Is always 0 in the NextProperty() for WriteStackFrame in the case of an async serialize on a boxed value.