[Inheritence] Setting base type can merge 2 different relationships

[smitpatel]

When base type and derived type both have relationship with one entity and if the relationships use same foreignkey properties (configured by conventions) then while setting base type, relationship from derived type is removed even though both relationships are different (navigationToDependent is different)

Repro:

public class AnEntity
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public BaseReference BaseReference { get; set; }
        public DerivedReference DerivedReference { get; set; }
    }

    public class BaseReference
    {
        [NotMapped]
        public int Id { get; set; }
        public string Name { get; set; }

        public int? BaseParentId { get; set; }
        [NotMapped]
        public AnEntity BaseParent { get; set; }
    }

    public class DerivedReference : BaseReference
    {
    }

    public class MyContext : DbContext
    {
        public DbSet<AnEntity> DerivedEntities { get; set; }

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            optionsBuilder.UseSqlServer(
                @"Server=(localdb)\MSSQLLocalDB;Database=_TestApp6;Integrated Security=True;MultipleActiveResultSets=True;Connect Timeout=30");
        }

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            modelBuilder.Entity<AnEntity>().HasOne(e => e.BaseReference).WithOne();
            modelBuilder.Entity<AnEntity>().HasOne(e => e.DerivedReference).WithOne();

            modelBuilder.Entity<AnEntity>().HasKey(e => e.Id);

            modelBuilder.Entity<DerivedReference>().BaseType<BaseReference>();

            modelBuilder.Entity<BaseReference>().HasKey(e => e.Id);
        }
    }

Console.WriteLine(context.Model.GetEntityType(typeof(BaseReference)).GetForeignKeys().Count());
Console.WriteLine(context.Model.GetEntityType(typeof(DerivedReference)).GetForeignKeys().Count());

//expected output
1
2
//actual output
1
1

[smitpatel]

This does not repro anymore 😌
@AndriySvyryd - This was reported during beta 8 when we did not have BaseTypeDiscoveryConvention. In latest code, base type is set even before relationships are configured. Any test scenario to cover this?

[AndriySvyryd]

We don't have many tests for relatinships with inheritance and NotMapped, so you can just add this repro as a test

[smitpatel]

Just now remembered this is from our test fixture only.
https://github.com/aspnet/EntityFramework/blob/788aee079f6aec2b077113f18cec82322da09336/test/Microsoft.EntityFrameworkCore.FunctionalTests/InheritanceRelationshipsQueryFixtureBase.cs#L63

I will remove work-around to see if it works else add test in model builder tests

[AndriySvyryd]

You can add tests that use the same model, but Assert that the model shape is correct