Associations with ExpressionPredicate are lost when query is joined

The test entity:

[Table(Name = User.TableName)]
	public class User : EntityBase
	{
		internal const string TableName = "Users";

		[PrimaryKey, Identity]
		[Column(Name = "Id")]
		public override int Id { get; set; }

		[Column(Name = "Name")]
		public string Name { get; set; }

		[Column(Name = "IsActive")]
		public bool IsActive { get; set; }

		[Column(Name = "Guid")]
		public Guid Guid { get; set; }

		[Column(Name = "AppointmentId")]
		public int? AppointmentId { get; set; }

		[Association(ThisKey = "AppointmentId", OtherKey = "Id", CanBeNull = true, Relationship = Relationship.ManyToOne,
			KeyName = "FK_Users_AppointmentId",
			BackReferenceName = "Users")]
		public virtual Appointment Appointment { get; set; }

		[Column]
		public int? ParentUserId { get; set; }

		[Association(CanBeNull = true, ExpressionPredicate = nameof(ParentPredicate))]
		public User Parent { get; set; }

		public static Expression<Func<User, User, bool>> ParentPredicate => (u1, u2) =>
		  u1.ParentUserId == u2.Id && u2.IsActive;
	}

Test methods

[Test]
public void Linq2DBOtherTests_Bug_With_Expression_Predicate_OK()
{
	using (var db = GetDataConnection())
	{
		var q123 = from x in db.GetTable<User>()
					select new
					{
						x.Id,
						ParentName = x.Parent.Name,
						AppointmentName = x.Appointment.Name
					};

		q123.ToList();
	}
}

[Test]
public void Linq2DBOtherTests_Bug_With_Expression_Predicate_Fail()
{
	using (var db = GetDataConnection())
	{
		// something to join. Anything. Let's say, that here is id selection from some permission view
		var p1 = db.Users.Where(x => x.Id == 123);

		var q123 = from x in db.GetTable<User>()
					join p in p1 on x.Id equals p.Id
					select new
					{
						x.Id,
						ParentName = x.Parent.Name,
						AppointmentName = x.Appointment.Name
					};

		q123.ToList();
	}
}

Without joining associations properties selection works well:

SELECT
	[t3].[Id],
	[t1].[Name],
	[t2].[Name] as [Name1]
FROM
	[Users] [t3] WITH (NOLOCK)
		LEFT JOIN [Users] [t1] ON [t3].[ParentUserId] = [t1].[Id] AND 1 = [t1].[IsActive]
		LEFT JOIN [Appointments] [t2] ON [t3].[AppointmentId] = [t2].[Id]

But with any join generated SQL doesn’t have selection for association properties

SELECT
	[x].[Id]
FROM
	[Users] [x] WITH (NOLOCK)
WHERE
	[x].[Id] = 123

Environment details

linq2db: 2.0.0 provider: SqlServerVersion.v2012

[sdanyliv]

It is not easy, but why not to start 😃 It took 2 years for me to understand 80% of code. Start from setting break-point to AssociationDescriptor constructor.

[sdanyliv]

Great, saving our time 😃