JsonSerializer throws serializing new object() with JsonSerializerDefaults.Web

[wannvmi]

Describe the bug

I found use return new object() will throw exception in .Net6 !

To Reproduce

this is Code
a minimal web API
Program.cs

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();

var app = builder.Build();

// Configure the HTTP request pipeline.
if (app.Environment.IsDevelopment())
{
    app.UseSwagger();
    app.UseSwaggerUI();
}

app.MapGet("/test", () => new object());

app.Run();

Exceptions

curl -X 'GET' 'http://localhost:5066/test' -H 'accept: application/json'

      An unhandled exception has occurred while executing the request.
      System.InvalidOperationException: Operation is not valid due to the current state of the object.
         at System.Text.Json.Serialization.JsonConverter`1.WriteNumberWithCustomHandling(Utf8JsonWriter writer, T value, JsonNumberHandling handling)
         at System.Text.Json.Serialization.JsonConverter`1.TryWrite(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)
         at System.Text.Json.Serialization.JsonConverter`1.WriteCore(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)
         at System.Text.Json.JsonSerializer.WriteCore[TValue](JsonConverter jsonConverter, Utf8JsonWriter writer, TValue& value, JsonSerializerOptions options, WriteStack& state)
         at System.Text.Json.JsonSerializer.WriteStreamAsync[TValue](Stream utf8Json, TValue value, JsonTypeInfo jsonTypeInfo, CancellationToken cancellationToken)
         at System.Text.Json.JsonSerializer.WriteStreamAsync[TValue](Stream utf8Json, TValue value, JsonTypeInfo jsonTypeInfo, CancellationToken cancellationToken)
         at System.Text.Json.JsonSerializer.WriteStreamAsync[TValue](Stream utf8Json, TValue value, JsonTypeInfo jsonTypeInfo, CancellationToken cancellationToken)
         at Microsoft.AspNetCore.Http.HttpResponseJsonExtensions.WriteAsJsonAsyncSlow[TValue](Stream body, TValue value, JsonSerializerOptions options, CancellationToken cancellationToken)
         at Microsoft.AspNetCore.Http.RequestDelegateFactory.ExecuteObjectReturn(Object obj, HttpContext httpContext)
         at Microsoft.AspNetCore.Routing.EndpointMiddleware.<Invoke>g__AwaitRequestTask|6_0(Endpoint endpoint, Task requestTask, ILogger logger)
         at Swashbuckle.AspNetCore.SwaggerUI.SwaggerUIMiddleware.Invoke(HttpContext httpContext)
         at Swashbuckle.AspNetCore.Swagger.SwaggerMiddleware.Invoke(HttpContext httpContext, ISwaggerProvider swaggerProvider)
         at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.Invoke(HttpContext context)

Further technical details

• ASP.NET Core version: 6.0.100
• The IDE (VS / VS Code/ VS4Mac) you're running on, and its version: Visual Studio 2022 17.0.1
• Include the output of dotnet --info:
  PS> dotnet --info
  .NET SDK (反映任何 global.json):
  Version: 6.0.100
  Commit: 9e8b04bbff

运行时环境:
OS Name: Windows
OS Version: 10.0.19043
OS Platform: Windows
RID: win10-x64
Base Path: C:\Program Files\dotnet\sdk\6.0.100\

[halter73]

This looks to be an issue with JsonSerializer when serializing object using JsonSerializerDefaults.Web.

using System.Text.Json;

// The following works:
await JsonSerializer.SerializeAsync(Stream.Null, new object(),
    new JsonSerializerOptions(JsonSerializerDefaults.General));

await JsonSerializer.SerializeAsync(Stream.Null, new { },
    new JsonSerializerOptions(JsonSerializerDefaults.Web));

// The following throws:
await JsonSerializer.SerializeAsync(Stream.Null, new object(),
    new JsonSerializerOptions(JsonSerializerDefaults.Web));

The above Program.cs results in the following output when built and run using the 6.0.100 SDK.

C:\dev\halter73\JsonSerializeObject> dotnet run
Unhandled exception. System.InvalidOperationException: Operation is not valid due to the current state of the object.
   at System.Text.Json.Serialization.JsonConverter`1.WriteNumberWithCustomHandling(Utf8JsonWriter writer, T value, JsonNumberHandling handling)
   at System.Text.Json.Serialization.JsonConverter`1.TryWrite(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.JsonConverter`1.WriteCore(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.JsonSerializer.WriteCore[TValue](JsonConverter jsonConverter, Utf8JsonWriter writer, TValue& value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.JsonSerializer.WriteStreamAsync[TValue](Stream utf8Json, TValue value, JsonTypeInfo jsonTypeInfo, CancellationToken cancellationToken)
   at System.Text.Json.JsonSerializer.WriteStreamAsync[TValue](Stream utf8Json, TValue value, JsonTypeInfo jsonTypeInfo, CancellationToken cancellationToken)
   at System.Text.Json.JsonSerializer.WriteStreamAsync[TValue](Stream utf8Json, TValue value, JsonTypeInfo jsonTypeInfo, CancellationToken cancellationToken)
   at Program.<Main>$(String[] args) in C:\dev\halter73\JsonSerializeObject\Program.cs:line 11
   at Program.<Main>(String[] args)

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Issue Details

---

Describe the bug

I found use return new object() will throw exception in .Net6 !

To Reproduce

this is Code
a minimal web API
Program.cs

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();

var app = builder.Build();

// Configure the HTTP request pipeline.
if (app.Environment.IsDevelopment())
{
    app.UseSwagger();
    app.UseSwaggerUI();
}

app.MapGet("/test", () => new object());

app.Run();

Exceptions

curl -X 'GET' 'http://localhost:5066/test' -H 'accept: application/json'

      An unhandled exception has occurred while executing the request.
      System.InvalidOperationException: Operation is not valid due to the current state of the object.
         at System.Text.Json.Serialization.JsonConverter`1.WriteNumberWithCustomHandling(Utf8JsonWriter writer, T value, JsonNumberHandling handling)
         at System.Text.Json.Serialization.JsonConverter`1.TryWrite(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)
         at System.Text.Json.Serialization.JsonConverter`1.WriteCore(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)
         at System.Text.Json.JsonSerializer.WriteCore[TValue](JsonConverter jsonConverter, Utf8JsonWriter writer, TValue& value, JsonSerializerOptions options, WriteStack& state)
         at System.Text.Json.JsonSerializer.WriteStreamAsync[TValue](Stream utf8Json, TValue value, JsonTypeInfo jsonTypeInfo, CancellationToken cancellationToken)
         at System.Text.Json.JsonSerializer.WriteStreamAsync[TValue](Stream utf8Json, TValue value, JsonTypeInfo jsonTypeInfo, CancellationToken cancellationToken)
         at System.Text.Json.JsonSerializer.WriteStreamAsync[TValue](Stream utf8Json, TValue value, JsonTypeInfo jsonTypeInfo, CancellationToken cancellationToken)
         at Microsoft.AspNetCore.Http.HttpResponseJsonExtensions.WriteAsJsonAsyncSlow[TValue](Stream body, TValue value, JsonSerializerOptions options, CancellationToken cancellationToken)
         at Microsoft.AspNetCore.Http.RequestDelegateFactory.ExecuteObjectReturn(Object obj, HttpContext httpContext)
         at Microsoft.AspNetCore.Routing.EndpointMiddleware.<Invoke>g__AwaitRequestTask|6_0(Endpoint endpoint, Task requestTask, ILogger logger)
         at Swashbuckle.AspNetCore.SwaggerUI.SwaggerUIMiddleware.Invoke(HttpContext httpContext)
         at Swashbuckle.AspNetCore.Swagger.SwaggerMiddleware.Invoke(HttpContext httpContext, ISwaggerProvider swaggerProvider)
         at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.Invoke(HttpContext context)

Further technical details

• ASP.NET Core version: 6.0.100
• The IDE (VS / VS Code/ VS4Mac) you're running on, and its version: Visual Studio 2022 17.0.1
• Include the output of dotnet --info:
  PS> dotnet --info
  .NET SDK (反映任何 global.json):
  Version: 6.0.100
  Commit: 9e8b04bbff

运行时环境:
OS Name: Windows
OS Version: 10.0.19043
OS Platform: Windows
RID: win10-x64
Base Path: C:\Program Files\dotnet\sdk\6.0.100\

Author:	wannvmi
Assignees:	halter73
Labels:	area-System.Text.Json, untriaged
Milestone:	-

[wannvmi]

NumberHandling = System.Text.Json.Serialization.JsonNumberHandling.Strict can fix it.

using System.Text.Json;

// The following throws:
var res1 = JsonSerializer.Serialize(new object(), new JsonSerializerOptions(JsonSerializerDefaults.Web));
Console.WriteLine(res1);

// this works
var res2 = JsonSerializer.Serialize(new object(), new JsonSerializerOptions(JsonSerializerDefaults.Web)
{
    NumberHandling = System.Text.Json.Serialization.JsonNumberHandling.Strict
});
Console.WriteLine(res2);

the code in

runtime/src/libraries/System.Text.Json/src/System/Text/Json/Serialization/JsonSerializerOptions.cs

Line 142 in f9dfd41

public JsonSerializerOptions(JsonSerializerDefaults defaults) : this()

[eiriktsarpalis]

Minimal reproduction:

using System.Text.Json;
using System.Text.Json.Serialization;

var options = new JsonSerializerOptions { NumberHandling = JsonNumberHandling.AllowReadingFromString };
JsonSerializer.Serialize(new object(), options);

This is a regression introduced by #54436. Changes in how polymorphic serialization for object instances is implemented means that serialized values specifically of type object (i.e. new object() instances) are handled by ObjectConverter rather than JsonConverterOfT.TryWrite. However, while ObjectConverter is overriding the ReadNumberWithCustomHandling method it does not override WriteNumberWithCustomHandling, resulting in the reported error when custom number handling is specified.

I've posted PR #62020 which fixes the problem. We might consider that change for servicing, however I find the new object() scenario to be a somewhat artificial corner case. Thoughts @ericstj @layomia?