When I want to add an manage_relationship change to a create/update action, all the examples I see use an argument for it with :map

update :something do
  argument :bla, :map

  change manage_relationship(:bla, type: :create, on_no_match: :create)
end

This works, but it makes create apis a little bit cumbersome since :bla can be a map with anything inside.

For example, using AshTypescript in the above action, will make :bla argument be any instead of a proper typed class.

I tried doing something like this:

update :something do
  argument :bla, :struct do
    constraints instance_of: Bla
  end

  change manage_relationship(:bla, type: :create, on_no_match: :create)
end

This will generate the correct type, but, it will fail because it will expect now that my :bla argument contains :id, :inserted_at and :updated__at

I’m wondering, is there a proper way to do this? I could keep it a map and add constraints for the keys, but that just means that every time I change Bla, I need to remember that there is this action that I need to update the input too.

Basically, what I think this should do is if I use the struct, it would filter the resource attribute for only its writable attributes and use this as the argument possible keys.

For example:

# This one contains :id, :inserted_at and :updated_at, so, it doesn't work
iex(4)> Bla |> Ash.Resource.Info.attributes() |> Enum.map(& &1.name)
[:id, :licenses, :units_sold_last_12_months, :amount_sold_last_12_months,
 :inserted_at, :updated_at, :user_id]

# This one filters not writable fields, so it should work
iex(3)> Bla |> Ash.Resource.Info.attributes() |> Enum.filter(& &1.writable?) |> Enum.map(& &1.name)
[:licenses, :units_sold_last_12_months, :amount_sold_last_12_months, :user_id]