Query :: errors for some queries with navigations and DefaultIfEmpty

[maumar]

Repro:

    class Program
    {
        static void Main(string[] args)
        {
            using (var ctx = new MyContext())
            {
                ctx.Database.EnsureDeleted();
                ctx.Database.EnsureCreated();

                var l1 = new GameFile { OriginalFilename = "GF1", Filename = "FN1", ContentType = "CT1" };
                var l2 = new GameFile { OriginalFilename = "GF2", Filename = "FN1", ContentType = "CT1" };

                var d1 = new GameDetails { Logo = l1 };
                var d2 = new GameDetails { Logo = l2 };

                var g1 = new Game { Title = "Game1", Details = d1 };
                var g2 = new Game { Title = "Game2", Details = d2 };
                var g3 = new Game { Title = "Game3" };
                var g4 = new Game { Title = "Game4" };

                ctx.Games.AddRange(g1, g2, g3, g4);
                ctx.GameDetails.AddRange(d1, d2);
                ctx.GameFiles.AddRange(l1, l2);
                ctx.SaveChanges();
            }

            using (var ctx = new MyContext())
            {
               // exception during flattening
               var query1 = ctx.Games
                   .Include(g => g.Details)
                   .ThenInclude(d => d.Logo)
                   .DefaultIfEmpty()
                   .Select(g => new { Logo = g.Details.Logo, g.Title, g.GameId })
                   .ToList();

                // invalid SQL
                var query2 = ctx.Games
                    .Include(g => g.Details)
                    .ThenInclude(d => d.Logo)
                    .DefaultIfEmpty()
                    .Select(g => new { Logo = (GameFile)null, g.Title, g.GameId })
                    .ToList();
            }
        }
    }

    public class Game
    {
        public int GameId { get; set; }
        public string Title { get; set; }
        public GameDetails Details { get; set; }
    }

    public class GameDetails
    {
        public int GameDetailsId { get; set; }
        public int GameId { get; set; }
        public GameFile Logo { get; set; }
}

    public class GameFile
    {
        public Guid GameFileId { get; private set; }
        public string ContentType { get; set; }
        public string Filename { get; set; }
        public string OriginalFilename { get; set; }
    }

    public class MyContext : DbContext
    {
        public DbSet<Game> Games { get; set; }
        public DbSet<GameDetails> GameDetails { get; set; }
        public DbSet<GameFile> GameFiles { get; set; }

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            modelBuilder.Entity<GameFile>().Property(p => p.Filename).IsRequired(true);
        }

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            optionsBuilder.UseSqlServer(@"Server=.;Database=Repro6207;Trusted_Connection=True;MultipleActiveResultSets=true");
        }
    }

First query thows error during compilation (during flattening), second query produces incorrect SQL

Invalid SQL that is produced:

SELECT [t2].[Title], [t2].[GameId]
                FROM (
                    SELECT [t10].*
                    FROM (
                        SELECT NULL AS [empty]
                    ) AS [empty10]
                    LEFT JOIN (
                        SELECT [g0].*
                        FROM [Games] AS [g0]
                    ) AS [t1] ON 1 = 1
                ) AS [t2]

[devseal]

Hello,
When is this issue going to be resolved?

[smitpatel]

Poaching this. Similar to #6636