I want to add an aggregate that returns the count of children based on the children relationship but it is throwing :count is not a valid type. It seems like Ash expect types other than :count, but when I consulted Ash.Resource.Builder — ash v3.29.3, it appeared to me that :count should work.

What could I be getting wrong?

I am using Ash.DataLayer.Ets data layer.

defmodule MyExtension.Transformers.AddChildrenCountAggregate do
  use Spark.Dsl.Transformer

  def transform(dsl_state) do
    Ash.Resource.Builder.add_new_aggregate(
      dsl_state,
      :count_of_children,
      :count,
      :children
    )
  end
end

throws

:count is not a valid type.

Valid types include any custom types, or the following short codes (alongside the types they map to):

  :map -> Ash.Type.Map
  :keyword -> Ash.Type.Keyword
  :term -> Ash.Type.Term
  :atom -> Ash.Type.Atom
  :tuple -> Ash.Type.Tuple
  :string -> Ash.Type.String
  :integer -> Ash.Type.Integer
  :file -> Ash.Type.File
  :float -> Ash.Type.Float
  :duration_name -> Ash.Type.DurationName
  :function -> Ash.Type.Function
  :boolean -> Ash.Type.Boolean
  :struct -> Ash.Type.Struct
  :uuid -> Ash.Type.UUID
  :uuid_v7 -> Ash.Type.UUIDv7
  :binary -> Ash.Type.Binary
  :date -> Ash.Type.Date
  :time -> Ash.Type.Time
  :time_usec -> Ash.Type.TimeUsec
  :decimal -> Ash.Type.Decimal
  :ci_string -> Ash.Type.CiString
  :naive_datetime -> Ash.Type.NaiveDatetime
  :utc_datetime -> Ash.Type.UtcDatetime
  :utc_datetime_usec -> Ash.Type.UtcDatetimeUsec
  :datetime -> Ash.Type.DateTime
  :duration -> Ash.Type.Duration
  :url_encoded_binary -> Ash.Type.UrlEncodedBinary
  :union -> Ash.Type.Union
  :module -> Ash.Type.Module
  :vector -> Ash.Type.Vector