Exclude only base type table from Migrations

[ajcvickers]

Originally filed as #2725 (comment) by VeMike

So how would I ignore just a base class, but not a derived class using this approach?

Consider the following model:

[Table(nameof(Human))]
public class Human
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int HumanId { get; set; }
    
    public int Age { get; set; }
}

[Table(nameof(Developer))]
public class Developer : Human
{
    public string MainLanguage { get; set; }
}

The database context for this model is the following

public class FooContext : DbContext
{
    public DbSet<Developer> Developers { get; set; } = null!;

    /// <inheritdoc />
    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        base.OnModelCreating(modelBuilder);

        // This is made to get TPT
        modelBuilder.Entity<Human>().ToTable(nameof(Human));
        modelBuilder.Entity<Developer>().ToTable(nameof(Developer));
        
        modelBuilder.Entity<Human>().ToTable(nameof(Human), t => t.ExcludeFromMigrations());
    }

    /// <inheritdoc />
    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        base.OnConfiguring(optionsBuilder);

        optionsBuilder.UseSqlServer("<FooBarConnectionString>");
    }
}

As you can see I only want Developer to be in the migration. Human should be excluded. Why would I want to do this? I am extending an existing model and the base (Human) already exists in the database. I want to add Developer to this existing model.

But if I create a migration the whole hierarchy of Human is excluded (basically all classes of type Human). But I want the Developer to be created.

Of course, I could just remove the line

modelBuilder.Entity<Human>().ToTable(nameof(Human), t => t.ExcludeFromMigrations());

and then manually remove the added Human from the migration. But is there a way to do this automatically?

[AndriySvyryd]

Note to implementor:

Add TPC condition to:

efcore/src/EFCore.Relational/Extensions/RelationalEntityTypeExtensions.cs

Lines 1455 to 1458 in 03bb7b7

	if (entityType.BaseType != null)
	{
	return entityType.GetRootType().IsTableExcludedFromMigrations();
	}

Also check that the dependent is mapped to the same table in:

efcore/src/EFCore.Relational/Extensions/RelationalEntityTypeExtensions.cs

Lines 1461 to 1465 in 03bb7b7

	if (ownership != null
	&& ownership.IsUnique)
	{
	return ownership.PrincipalEntityType.IsTableExcludedFromMigrations();
	}

Change to ||:

efcore/src/EFCore.Relational/Migrations/Internal/MigrationsModelDiffer.cs

Lines 560 to 561 in 03bb7b7

	if (source.IsExcludedFromMigrations
	&& target.IsExcludedFromMigrations)

Check IsExcludedFromMigrations in:

efcore/src/EFCore.Relational/Migrations/Internal/MigrationsModelDiffer.cs

Lines 2201 to 2202 in 03bb7b7

	r => r.EntityState is EntityState.Added or EntityState.Modified
	|| (r.EntityState is EntityState.Deleted && diffContext.FindDrop(r.Table!) == null));

[ajcvickers]

Note from triage: this is a bug, but fix should be documented as a breaking change since TPT cases where all tables were excluded will now only exclude the base table.