[Bug]: Required nested properties are marked required even if outer property is optional

[drauch]

Describe the bug

Consider the following model:

public record Model ( Inner? inner, [Required] string other );
public record Inner ( [Required] string prop );

The model is used in an ASP.NET Core action like this:

public IActionResult MyAction ( [FromForm, Required] Model model )

It translates the nested models to a flattened representation of dot-concatenated properties, i.e., inner.prop - unfortunately, this property is set to required which is not true.

Expected behavior

The property should be optional.

Actual behavior

The property is marked as required.

Steps to reproduce

See description.

Exception(s) (if any)

No response

Swashbuckle.AspNetCore version

8

.NET Version

8

Anything else?

No response

[drauch]

Note, this seems to happen only for multipart/form-data, as there seems to be a flattening-mechanism applied which is not used for other body types which correctly produce nested schemas.

[npenza]

I'd be happy to help with this if it hasn't already been worked on, otherwise I'll start looking into it.