TPT: Base type key field name is taken from derived type

[oleneveu]

Context

I have to map an existing database to EFC5, and I want to take advantage of the Table-Per-Type feature.
Consider the following two tables, paying attention to the names of the PK fields:

CREATE TABLE [Identity](
	[IdentityId] [int] IDENTITY(1,1) NOT NULL,
	[Name] [nvarchar](64) NULL,
	-- (...)
	CONSTRAINT [PK_Identity] PRIMARY KEY CLUSTERED ( [IdentityId] ASC )
) ON [PRIMARY]
GO

CREATE TABLE [User](
	[UserId] [int] NOT NULL,
	[Email] [nvarchar](100) NOT NULL,
	-- (...)
	CONSTRAINT [PK_User] PRIMARY KEY CLUSTERED ( [UserId] ASC )
)
GO

ALTER TABLE [dbo].[User]  WITH CHECK ADD  CONSTRAINT [Ctr_User_UserId] FOREIGN KEY([UserId])
REFERENCES [dbo].[Identity] ([IdentityId])
GO

They are mapped to these entities:

    public partial class Identity
    {
        [Key]
        public int Id { get; set; }
        public string Name { get; set; }
        // (...)
    }

    public partial class User : Identity
    {
        public string Email { get; set; }
        // (...)
    }

The column names are declared here:

            modelBuilder.Entity<Identity>(entity =>
            {
                entity.Property(e => e.Id).HasColumnName("IdentityId");
            });

            modelBuilder.Entity<User>(entity =>
            {
                entity.Property(u => u.Id).HasColumnName("UserId");
            });

Issue

EFC5 considers that the actual PK field name for the table 'Identity' is 'UserId' instead of 'IdentityId' as declared.
Any query will fail, and that behavior can be exposed when generating a migration:

            migrationBuilder.CreateTable(
                name: "Identity",
                columns: table => new
                {
                    UserId = table.Column<int>(type: "int", nullable: false) // !!! Should be 'IdentityId' !!!
                        .Annotation("SqlServer:Identity", "1, 1"),
                    Name = table.Column<string>(type: "nvarchar(64)", maxLength: 64, nullable: true),
                    // (...)
                },
                constraints: table =>
                {
                    table.PrimaryKey("PK_Identity", x => x.UserId);
                });

            migrationBuilder.CreateTable(
                name: "User",
                columns: table => new
                {
                    UserId = table.Column<int>(type: "int", nullable: false),
                    Email = table.Column<string>(type: "nvarchar(100)", maxLength: 100, nullable: false),
                    // (...)
                },
                constraints: table =>
                {
                    table.PrimaryKey("PK_User", x => x.UserId);
                });

This database was actually previously mapped to an EF6 model, using the TPT feature for these tables.

Provider and version information

EF Core version: 5.0.0
Database provider: Microsoft.EntityFrameworkCore.SqlServer
Target framework: .NET 5.0
Operating system: Windows 10.0.19041.572
IDE: Visual Studio 2019 16.8.2

[oleneveu]

Here is a small project that reproduces the issue.
Just add a migration to see the generated model.

using Microsoft.EntityFrameworkCore;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;

namespace EFCoreBug
{
    class Program
    {
        class TestDbContext : DbContext
        {
            protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
            {
                optionsBuilder.UseSqlServer("Server=(localdb)\\MSSQLLocalDB;initial catalog=EFC5_TPT;Integrated Security=true");
            }

            protected override void OnModelCreating(ModelBuilder modelBuilder)
            {
                base.OnModelCreating(modelBuilder);
                modelBuilder.Entity<Identity>().Property(u => u.Id).HasColumnName("IdentityId");
                modelBuilder.Entity<User>().Property(u => u.Id).HasColumnName("UserId");

            }

            public DbSet<Identity> Identities { get; set; }
            public DbSet<User> Users { get; set; }
        }

        [Table("Identity")]
        class Identity
        {
            [Key]
            public int Id { get; set; }
            public string Name { get; set; }
        }

        [Table("User")]
        class User : Identity
        {
            public string Email { get; set; }
        }

        static void Main(string[] args)
        {
        }
    }
}

Migration:

        protected override void Up(MigrationBuilder migrationBuilder)
        {
            migrationBuilder.CreateTable(
                name: "Identity",
                columns: table => new
                {
                    UserId = table.Column<int>(type: "int", nullable: false)
                        .Annotation("SqlServer:Identity", "1, 1"),
                    Name = table.Column<string>(type: "nvarchar(max)", nullable: true)
                },
                constraints: table =>
                {
                    table.PrimaryKey("PK_Identity", x => x.UserId);
                });

            migrationBuilder.CreateTable(
                name: "User",
                columns: table => new
                {
                    UserId = table.Column<int>(type: "int", nullable: false),
                    Email = table.Column<string>(type: "nvarchar(max)", nullable: true)
                },
                constraints: table =>
                {
                    table.PrimaryKey("PK_User", x => x.UserId);
                    table.ForeignKey(
                        name: "FK_User_Identity_UserId",
                        column: x => x.UserId,
                        principalTable: "Identity",
                        principalColumn: "UserId",
                        onDelete: ReferentialAction.Restrict);
                });
        }

[ajcvickers]

Duplicate of #19811