[Bug]: Behavior change with UseOneOfForPolymorphism and abstract classes from version 7.0.0 and version 7.2.0

[fenzad]

Describe the bug

I notice a change in the generation of the open API in this situation:

public abstract class A {
public string? PropA { get; set; }
}

public class B: A
{
public string? PropB { get; set; }
}

public class C: B
{
public string? PropC { get; set; }
}

public class TestController : ControllerBase
{
[HttpPost]
public ActionResult Post(A model)
{
return Ok();
}
}

builder.Services.AddSwaggerGen(c =>
{
c.SwaggerDoc("v1", new OpenApiInfo { Title = "My API", Version = "v1" });
c.UseOneOfForPolymorphism();
c.SelectSubTypesUsing(t => typeof(A) == t ? [typeof(C)] : []);
});

Expected behavior

With version 7.0.0, the behavior is correct.

Actual behavior

With version 7.2.0, the properties of class B are missing.

Steps to reproduce

I am attaching the test solution, which currently references version 7.0.0 to test the correct case. To test the incorrect case with the new version, just update the references in the csproj to 7.2.0

TestSwagger.zip

Exception(s) (if any)

No response

Swashbuckle.AspNetCore version

7.0.0 and 7.2.0

.NET Version

net9.0

Anything else?

No response

[martincostello]

Do you mean 7.2.0? There is no 7.0.2.

[fenzad]

7.2.0

[fenzad]

The issue is resolved by specifying in SelectSubTypesUsing:
c.SelectSubTypesUsing(t => typeof(A) == t ? [typeof(C)] : typeof(B) == t ? [typeof(C)] : []);
However, this is a different behavior compared to the previous version…

[martincostello]

To help narrow down where the regression happened, do you get the right behaviour with 7.1.0?

[fenzad]

The correct behavior (which at this point I don’t know if it was more correct before or now) is up to and including version 7.0.0. From version 7.1.0, there has been a change.