Generated migration code doesn't compile when combining owned entities with base types.

[nphmuller]

I believe this scenario is not supported. It would be more clear if a user friendly error message got shown during the migration creation instead of this vague compile error.

Repro:

    public class MyContext : DbContext
    {

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            modelBuilder.Entity<LessThanFriend>().OwnsOne(e => e.Address);
            modelBuilder.Entity<FullAddress>().HasBaseType<CityAddress>();
        }
    }

    public class LessThanFriend
    {
        public int Id { get; set; }
        public string Name { get; set; }

        public CityAddress Address { get; set; }
    }

    public class CityAddress
    {
        public string Cap { get; set; }
        public string City { get; set; }
    }

    public class FullAddress : CityAddress
    {
        public string Street { get; set; }
    }

• Run dotnet ef migrations add Initial
• Run dotnet build.

The following compile error is thrown:

Migrations\MyContextModelSnapshot.cs(52,29): error CS1929: 'ReferenceOwnershipBuilder' does not contain a definition for 'HasDiscriminator' and the best extension method overload 'RelationalEntityTypeBuilderExtensions.HasDiscriminator<string>(EntityTypeBuilder, string)' requires a receiver of type 'EntityTypeBuilder' [C:\Users\mulle\source\repos\ConsoleApp10\ConsoleApp10\ConsoleApp10.csproj]
Migrations\20181113112638_initial.Designer.cs(54,29): error CS1929: 'ReferenceOwnershipBuilder' does not contain a definition for 'HasDiscriminator' and the best extension method overload 'RelationalEntityTypeBuilderExtensions.HasDiscriminator<string>(EntityTypeBuilder, string)' requires a receiver of type 'EntityTypeBuilder' [C:\Users\mulle\source\repos\ConsoleApp10\ConsoleApp10\ConsoleApp10.csproj]

This is the part of the generated code that causes the compile error:

modelBuilder.Entity("ConsoleApp10.LessThanFriend", b =>
                {
                    b.OwnsOne("ConsoleApp10.CityAddress", "Address", b1 =>
                        {
                            b1.HasDiscriminator<string>("Discriminator").HasValue("CityAddress");
                        });
                });

Basically b1 is of type ReferenceOwnershipBuilder. This type doesn't contain the method HasDiscriminator<>().

Further technical details

EF Core packages:

    <PackageReference Include="Microsoft.EntityFrameworkCore.Design" Version="2.1.4" />
    <PackageReference Include="Microsoft.EntityFrameworkCore.SqlServer" Version="2.1.4" />

Operating system: Windows 10 1809
IDE: VS 15.8.9

[nphmuller]

Duplicate of #9148