lib/absinthe/middleware/pass_parent.ex
defmodule Absinthe.Middleware.PassParent do
@moduledoc """
Middleware that just passes the parent down to the children.
This is the default resolver for subscription fields.
"""
@behaviour Absinthe.Middleware
def call(%{source: parent} = res, _) do
%{res | state: :resolved, value: parent}
end
end