OpenAPI generation *still* doesn't work with the simplest model with multiple collections in .net 9

[tijs-hendriks-mosadex]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

Using .net 9 and Microsoft.Extensions.ApiDescription.Server v9.0.5

This model:

public class TestModel
{
    public SubModel[] First { get; set; }
    public SubModel[] Second { get; set; }
}

public class SubModel
{
    public string Name { get; set; }
}

Generates this definition:

"TestModel": {
  "type": "object",
  "properties": {
    "first": {
      "type": "array",
      "items": {
        "$ref": "#/components/schemas/SubModel"
      }
    },
    "second": {
      "type": "array",
      "items": { } <<<<< NO TYPE REF HERE?
    }
  }
}

This is now the third time we've been waiting on a new release that was expected to include a fix for this issue. Given the ASP.NET release cadence, these delays are becoming quite impactful for us - we have multiple branches waiting that depend on this functionality.

Even very simple models are failing to work as expected. I had previously submitted this exact model in an earlier bug report: #60931

Could you clarify whether OpenAPI generation is currently considered stable and suitable for production use?

[martincostello]

Could you clarify whether OpenAPI generation is currently considered stable and suitable for production use?

As far as I'm aware, yes it is. But that's not to say there aren't any bugs.

[LiHaoGit]

I'm frustrated that this OpenAPI generation bug (missing type refs for multiple collections) persists in ASP.NET Core 9.0.4, despite prior expectations of a fix. This, plus other OpenAPI issues I've hit, makes it clear that the current state isn't production-ready for us.

When can we expect a definitive fix for this collection bug, and are there broader plans to stabilize OpenAPI generation in .NET 9? These recurring delays are significantly impacting our projects.