NullReferenceException when trying to seed a keyless entity

[roji]

Repro:

await using var ctx = new BlogContext();
await ctx.Database.EnsureDeletedAsync();
await ctx.Database.EnsureCreatedAsync();

public class BlogContext : DbContext
{
    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        => optionsBuilder.UseSqlServer(...);

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Blog>()
            .HasNoKey()
            .HasData(new Blog { Name = "foo" });
    }
}

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

Happens on both the latest 5.0 and 3.1.

[smitpatel]

Keyless entities don't have keys so they cannot be seeded using state manager based seeding implementation.
Should throw a better validation or need different implementation for seeding.
#22063

[umitkavala]

I'll have a look at this while I stuck at #23226 :)

[umitkavala]

// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.

using System.ComponentModel.DataAnnotations.Schema;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.EntityFrameworkCore.TestUtilities;
using Xunit;

namespace Microsoft.EntityFrameworkCore
{
    public abstract class SeedingTestBase
    {
        [ConditionalTheory]
        [InlineData(false)]
        [InlineData(true)]
        public virtual async Task Seeding_does_not_leave_context_contaminated(bool async)
        {
            using var context = CreateContextWithEmptyDatabase(async ? "1A" : "1S");
            var _ = async
                ? await context.Database.EnsureCreatedResilientlyAsync()
                : context.Database.EnsureCreatedResiliently();

            Assert.Empty(context.ChangeTracker.Entries());

            var seeds = context.Set<Seed>().OrderBy(e => e.Species).ToList();
            Assert.Equal(2, seeds.Count);
            Assert.Equal("Apple", seeds[0].Species);
            Assert.Equal("Orange", seeds[1].Species);
        }

        protected abstract SeedingContext CreateContextWithEmptyDatabase(string testId);

        protected abstract class SeedingContext : DbContext
        {
            public string TestId { get; }

            protected SeedingContext(string testId)
                => TestId = testId;

            protected override void OnModelCreating(ModelBuilder modelBuilder)
                => modelBuilder.Entity<Seed>()
                    .HasNoKey()
                    .HasData(
                    new Seed {  Species = "Apple" },
                    new Seed {  Species = "Orange" }
                );
        }

        protected class Seed
        {
            //[DatabaseGenerated(DatabaseGeneratedOption.None)]
            //public int Id { get; set; }

            public string Species { get; set; }
        }
    }
}

reproduced with test case. I'll continue from there

Its failing before Seeding when decide IsKeyUnknown:

var keyProperties = ((EntityType)EntityType).FindPrimaryKey().Properties // its null here