How to use DateTime in Absinthe

Hi, what’s up everyone?

I’d be very grateful if someone wiser the me could open up this following error message a bit:

DateTime.to_iso8601/2 expects format to be :extended or :basic, got: :extended

I read it over and over again but my logic just fails me. It wants :extended but gets :extended. Pretty deep and almost poetic but not very helpful…

I’d really fancy some datetimes on my Absinthe type, like this:

import_types Absinthe.Type.Custom

  object :user do
    field :id, :id
    field :updated_at, :datetime
    field :inserted_at, :datetime
  end

I also tried to use my own scalar type instead of the import_types, like this:

  scalar :datetime do
    parse fn input ->
      case DateTime.from_iso8601(input.value) do
        {:ok, datetime} -> {:ok, datetime}
        _ -> :error
      end
    end

    serialize fn datetime ->
      DateTime.to_iso8601(datetime)
    end
  end

…but this resulted the very same error message.

So what am I doing wrong or is there a better way to do this?