Filtering by whether a property (either navigation or string is null)

[dkokotov]

I'm using HotChocolate backed by an EF Core model. I would like to be able to use a filter to retrieve entities where some navigational property is null.

Eg, assume a data model like this

class Person {
    public string Id { get; set; } 
    public Car? Car { get; set; } // optional one-to-one mapping to Car
    public string Name { get; set; } 
} 

class Car {
    public string Id { get; set; }

    public string OwnerId { get; set; } 

    public Person Owner { get; set; }

    public string Make { get; set; }
}

class Query {
   [UseFiltering]
    public IQueryable<Person> GetPeople(MyDbContext dbCtx) => dbContext.Persons.AsQueryable();
} 

I would like to be able to get Persons who do not have a car (eg person.Car == null).

Is there a way to do this with the built-in filtering support, or does it require a custom filter operation? I would have expected something like this to be possible "out of the box", but i haven't figured out a way.