Inspect the data passed between GenStages.

stage_inspector.ex

defmodule StageInspector do
  alias Experimental.{GenStage}
  use GenStage

  def init(type) when type in [:consumer, :producer_consumer] do
    {type, type}
  end

  def handle_events(events, _from, state = :consumer) do
    Enum.each events, &inspect_event/1
    {:noreply, [], state}
  end
  def handle_events(events, _from, state = :producer_consumer) do
    Enum.each events, &inspect_event/1
    {:noreply, events, state}
  end

  defp inspect_event(event) when is_binary(event), do: IO.puts(event)
  defp inspect_event(event), do: IO.inspect(event)
end