Migration seed data does not respect "ValueGeneratedOnAddOrUpdate"

[thehe]

If you're using Seed-Data with EF.Migrations with Value-Generators, initial values are not created with "ValueGeneratedOnAddOrUpdate()" but only with "ValueGeneratedOnAdd()".

see my PR: #21865
Problem seems to be the equality-comparison of a flag enum!

Steps to reproduce

TimedEntity.cs (abstract)

    public abstract class TimedEntity
    {
        [Column("created_at")]
        public DateTimeOffset CreatedAt { get; }

        [Column("updated_at")]
        public DateTimeOffset UpdatedAt { get; } // notice: not nullable here!
    }

Voucher.cs

    [Table("vouchers")]
    public class Voucher : TimedEntity
    {
        [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
        [Column("id")]
        [Key]
        public long Id { get; set; }

        [Column("code"), StringLength(100)]
        public string Code { get; set; }
   }

Migrations seed data - OnConfiguring:

            var voucher = modelBuilder.Entity<Voucher>();
            voucher.Property(x => x.CreatedAt).ValueGeneratedOnAdd().HasValueGenerator<NowValueGenerator>();
            voucher.Property(x => x.UpdatedAt).ValueGeneratedOnAddOrUpdate().HasValueGenerator<NowValueGenerator>(); // notice: generate value on ADD *OR* UPDATE!

            voucher.HasData(new Voucher()
            {
                Code = "ABC1234",
                Id = 1
            });
           // no definition of createdAt or updatedAt here - should be filled out automatically

Results in:

            migrationBuilder.InsertData(
                table: "vouchers",
                columns: new[] { "id", "created_at", "code" },  // notice: "updated_at" missing here!
                values: new object[,]
                {
                    { 1L, new DateTimeOffset(new DateTime(2020, 8, 2, 22, 42, 6, 105, DateTimeKind.Unspecified).AddTicks(4450), "ABC1234" },
                });

Further technical details

EF Core version: 3.1.6
Database provider: Npgsql.EntityFrameworkCore.PostgreSQL (but irrelevant)
Target framework: .NET Core 3.1
Operating system: RHEL7, RHEL8, Win10 Enterprise 20H2
IDE: VSCode, Visual Studio 2019 pro

[AndriySvyryd]

@thehe ValueGenerated configuration only affects values generated by the database, you don't need to specify them when using a client value generator. Also a value generator isn't currently used when updating, see #6999

[thehe]

@AndriySvyryd I'm quite confused now:

Why there is "created_at" then in the seed data and not "updated_at"?
When it shouldn't do anything regarding the client-side ValueGenerator, then there shouldn't be any difference between resulting "createdAt" and "updatedAt"?
But "updatedAt" is just missing in seed data.

Can you please describe what's preventing "updated_at" to get popoluted by the same exact value-generator (which just pushes out "DateTimeOffset.UtcNow" as value)

[AndriySvyryd]

When you configure a property as ValueGeneratedOnAddOrUpdate EF assumes that the value will always be provided by the database, therefore one supplied in the insert operation would either be ignored or cause an error. However for ValueGeneratedOnAdd many databases do provide a way of provided a value that would override what would be generated by the database.

Usually the table auditing pattern is implemented purely on the database side, as that provides the most consistent values.