AutoMapper changed the behavior of AssertConfigurationIsValid() regarding ignored properties in v12. I can’t find anything in the release notes (https://docs.automapper.org/en/latest/12.0-Upgrade-Guide.html) to explain it.

This simple example passes the test in v11. In v12, it fails saying that NickName is unmapped, even though I’ve explicitly ignored it. The same issue occurs if I use MapFrom() instead of Ignore().

Is this behavior expected or is it a bug?

var c = new MapperConfiguration(cfg =>
{
    cfg.AddProfile<MyMappingProfile>();
});
c.AssertConfigurationIsValid();

////////////////////////////////

public class MyMappingProfile : Profile
{
    public MyMappingProfile()
    {
        // Fails in v11 up to v13.0.2-preview.0.3 because `Address` is unmapped
        //CreateMap<Customer, CustomerDTO>();

        // Passes in v11 up to v13.0.2-preview.0.3 because `Name and `NickName` are mapped
        //CreateMap<Customer, CustomerDTO>(MemberList.Source);

        // Passes in v11 because `Name is mapped and `NickName` is ignored
        // Fails v12 up to v13.0.2-preview.0.3. The error message says `NickName` is unmapped
        CreateMap<Customer, CustomerDTO>(MemberList.Source)
            .ForMember(d => d.NickName, o => o.Ignore())
            ;
    }
}

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

    public string NickName { get; set; }

}

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

    public string NickName { get; set; }

    public string Address { get; set; }
}