ModelBindingResult.Success not accepting null

[Muchiachio]

Describe the bug

We are testing preview bits on our application and we noticed that ModelBindingResult.Success no longer accepts null values with nullable annotations enabled. Is this intentional or a bug? We don't want to use ModelBindingResult.Failed as we explicitly binding the value to null and don't want other model binders to be used after.

Also didn't want to create new issues so here are other places with potentially incorrect nullability which don't compile now.

• IModelBinderProvider.GetBinder return should be nullable, example in codebase BinderTypeModelBinderProvider.
• IUrlHelper.IsLocalUrl(string) parameter should be nullable, for example checking login redirect which can be null, example in codebase UrlHelperBase which checks for null too.

To Reproduce

#nullable enable

public class ModelBinder : IModelBinder
{
    public Task BindModelAsync(ModelBindingContext bindingContext)
    {
        bindingContext.Result = ModelBindingResult.Success(null);

        return Task.CompletedTask;
    }
}

Further technical details

Version:   5.0.100-preview.8.20417.9
Commit:    fc62663a35

[pranavkm]

Thanks @Muchiachio for the feedback. We'll have these addressed for RC1