Microsoft.AspNetCore.OpenApi generates a class that does not exist but is like a other class with a number added to the end of the name

[SMAH1]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

I have asp dotnet 9.0 project.

I use Microsoft.AspNetCore.OpenApi to generate OpenAPI and use Scalar and SwaggerUI to show it.
my project file is

<Project Sdk="Microsoft.NET.Sdk.Web">

  <PropertyGroup>
    <TargetFramework>net9.0</TargetFramework>
    <Nullable>enable</Nullable>
    <ImplicitUsings>enable</ImplicitUsings>
    <InvariantGlobalization>true</InvariantGlobalization>
    <PublishAot>true</PublishAot>
	<OpenApiDocumentsDirectory>./</OpenApiDocumentsDirectory>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="Microsoft.AspNetCore.OpenApi" Version="9.0.0" />
    <PackageReference Include="Scalar.AspNetCore" Version="1.2.55" />
    <PackageReference Include="Swashbuckle.AspNetCore.SwaggerUI" Version="7.2.0" />
  </ItemGroup>

</Project>

and there are Monitoring api and class like this:

using System.Net;

namespace WebApiAotTest;

public class MonitoringItem
{
    public string[] Name { get; set; } = null!;
    public int value { get; set; }
}

public class MonitoringRoot
{
    public MonitoringItem Item1 { get; set; } = null!;
    public MonitoringItem Item2 { get; set; } = null!;
}

public static class MonitoringExtension
{
    public static void MonitoringApi(this WebApplication app)
    {
        var monitoringApi = app.MapGroup("/monitoring");

        monitoringApi.MapGet("/", () => new MonitoringRoot() )
            .Produces<MonitoringRoot>((int)HttpStatusCode.OK)
            .WithTags("Monitoring")
            .WithSummary("Get Monitoring")
            .WithDescription("This endpoint returns Monitoring data.");
    }
}

The API return MonitoringRoot that has multi MonitoringItem.

and program.cs is:

using Microsoft.AspNetCore.OpenApi;
using Microsoft.OpenApi.Models;
using Scalar.AspNetCore;
using System.Text.Json.Serialization;
using WebApiAotTest;

var builder = WebApplication.CreateSlimBuilder(args);

builder.Services.AddOpenApi(options =>
{
    options.AddDocumentTransformer((document, context, cancellationToken) =>
    {
        document.Info.Contact = new OpenApiContact
        {
            Name = "Contoso Support",
            Email = "support@contoso.com"
        };
        return Task.CompletedTask;
    });

    options.CreateSchemaReferenceId = (type) => type.Type.IsEnum ? null : OpenApiOptions.CreateDefaultSchemaReferenceId(type);
});

builder.Services.ConfigureHttpJsonOptions(options =>
{
    options.SerializerOptions.TypeInfoResolverChain.Insert(0, AppJsonSerializerContext.Default);
});

var app = builder.Build();

app.MapOpenApi("/openapi/v1/my.json");
app.UseSwaggerUI(opt =>
{
    opt.SwaggerEndpoint("/openapi/v1/my.json", "MyApi");
});
app.MapScalarApiReference(opt =>
{
    opt
        .WithTitle("MyApi")
        .WithOpenApiRoutePattern("/openapi/v1/{documentName}.json")
        .WithEndpointPrefix("/openapi/{documentName}")
        ;
});

app.MonitoringApi();
app.Run();

[JsonSerializable(typeof(MonitoringRoot))]
internal partial class AppJsonSerializerContext : JsonSerializerContext
{

}

API works OK. but when I see swagger, there is wrong data!

and (??!!!!):

also original json has wrong:

{
  "openapi": "3.0.1",
  "info": {
    "title": "WebApiAotTest | v1",
    "contact": {
      "name": "Contoso Support",
      "email": "support@contoso.com"
    },
    "version": "1.0.0"
  },
  "servers": [
    {
      "url": "http://localhost:5090"
    }
  ],
  "paths": {
    "/monitoring": {
      "get": {
        "tags": [
          "Monitoring"
        ],
        "summary": "Get Monitoring",
        "description": "This endpoint returns Monitoring data.",
        "responses": {
          "200": {
            "description": "OK",
            "content": {
              "application/json": {
                "schema": {
                  "$ref": "#/components/schemas/MonitoringRoot"
                }
              }
            }
          }
        }
      }
    }
  },
  "components": {
    "schemas": {
      "MonitoringItem": {
        "type": "object",
        "properties": {
          "name": {
            "type": "array",
            "items": {
              "type": "string"
            }
          },
          "value": {
            "type": "integer",
            "format": "int32"
          }
        }
      },
      "MonitoringItem2": {
        "type": "object",
        "properties": {
          "name": {
            "$ref": "#/components/schemas/#/properties/item1/properties/name"
          },
          "value": {
            "type": "integer",
            "format": "int32"
          }
        }
      },
      "MonitoringRoot": {
        "type": "object",
        "properties": {
          "item1": {
            "$ref": "#/components/schemas/MonitoringItem"
          },
          "item2": {
            "$ref": "#/components/schemas/MonitoringItem2"
          }
        }
      }
    }
  },
  "tags": [
    {
      "name": "Monitoring"
    }
  ]
}

There is MonitoringItem2 is json (generated by OpenAPI) but there is not in my code.

NOTE: MonitoringItem2 is exactly like MonitoringItem.
NOTE: If add Item3, Item4 , ... to MonitoringRoot, generate MonitoringItem3, MonitoringItem3, .... .
NOTE: I checked and found that the below code was causing this problem:

// in MonitoringItem
public string[] Name { get; set; }

so I remove array, everything is OK! like this:

public class MonitoringItem
{
    public string Name { get; set; } = null!;
    public int value { get; set; }
}

Expected Behavior

No generate extra data and I see:

Steps To Reproduce

No response

Exceptions (if any)

No response

.NET Version

9.0.100

Anything else?

I use Microsoft Visual Studio Community 2022 (64-bit) Version 17.12.2 in windows 10 22H2.

[captainsafia]

Closing in favor of #58968.

See the update I posted over at #58968 (comment).