When using SplitToTable, FKs are created for the wrong table

[AndreqGav]

Problem

I have a database with the Main and Details tables. The Blog table depends on Main. All this is reflected in the EF entities.

I want to combine the Main and Details entities without changing the database structure. I use SplitToTable for this. But after creating the migration, the foreign key: FK_Blog_Main_MainId is deleted and FK_Blog_Details_MainId is created instead.

Code

https://github.com/AndreqGav/efcore.example.split-to-table

At first, the entities look like this:

public class Main
{
    public int Id { get; set; }

    public string? Name { get; set; }

    public virtual Details? Details { get; set; }

    public Blog? Blog { get; set; }
}

public class Details
{
    public int Id { get; set; }

    public string? Description { get; set; }
}

public class Blog
{
    public int Id { get; set; }

    public string? Name { get; set; }

    public int? MainId { get; set; }

    public virtual Main? Main { get; set; }
}

EF Configuration:

modelBuilder.Entity<Main>(builder =>
{
    builder.HasOne(e => e.Details).WithOne()
        .HasForeignKey<Details>(e => e.Id);
});

modelBuilder.Entity<Details>(builder =>
{
    builder.HasKey(e => e.Id);
});

modelBuilder.Entity<Blog>(builder =>
{
    builder.HasKey(e => e.Id);

    builder.HasOne(e => e.Main).WithOne(e => e.Blog)
        .OnDelete(DeleteBehavior.Cascade)
        .HasForeignKey<Blog>(e => e.MainId);
});

After using SplitToTable

The Details class has been deleted

public class Main
{
    public int Id { get; set; }

    public string? Name { get; set; }

    // public virtual Details? Details { get; set; }

    public Blog? Blog { get; set; }

    #region Details

    public string? Description { get; set; }

    #endregion
}

EF Configuration:

modelBuilder.Entity<Main>(builder =>
{
    // builder.HasOne(e => e.Details).WithOne()
    //     .HasForeignKey<Details>(e => e.Id);

    builder.SplitToTable("Details", tb =>
    {
        tb.Property(e => e.Description);
    });
});

// modelBuilder.Entity<Details>(builder =>
// {
//     builder.HasKey(e => e.Id);
// });

modelBuilder.Entity<Blog>(builder =>
{
    builder.HasKey(e => e.Id);

    builder.HasOne(e => e.Main).WithOne(e => e.Blog)
        .OnDelete(DeleteBehavior.Cascade)
        .HasForeignKey<Blog>(e => e.MainId);
});

After migration

migrationBuilder.DropForeignKey(
    name: "FK_Blog_Main_MainId",
    table: "Blog");

migrationBuilder.AddForeignKey(
    name: "FK_Blog_Details_MainId",
    table: "Blog",
    column: "MainId",
    principalTable: "Details",
    principalColumn: "Id",
    onDelete: ReferentialAction.Cascade);

Include provider and version information

EF Core version:
Database provider: (e.g. Microsoft.EntityFrameworkCore.PostgreSQL)
Target framework: (e.g. .NET 9.0)

[AndriySvyryd]

I realize that the new FK looks weird, but since there's also an FK from Details.Id to Main.Id it still represents the same constraint in practice.
#27971 will allow to specify the target table.