my_compile_phase.ex

defmodule MyApi.Schema.Pipeline.MyCompilePhase do
  @moduledoc """
  based on Absinthe phases https://hexdocs.pm/absinthe/1.5.3/Absinthe.Phase.html
  """

  alias Absinthe.{Blueprint, Pipeline, Phase}
  alias Absinthe.Blueprint.Schema.{ObjectTypeDefinition, FieldDefinition}

  def pipeline(pipeline) do
    Pipeline.insert_after(pipeline, Phase.Schema.TypeImports, __MODULE__)
  end

  def run(blueprint = %Blueprint{}, _) do
    {:ok, Blueprint.prewalk(blueprint, &rename_library_types(&1))}
  end

  defp rename_library_types(struct = %ObjectTypeDefinition{module: _}) do
    do_process(struct, Module.split(struct.module))
  end

  defp rename_library_types(struct = %FieldDefinition{module: _}) do
    do_process(struct, Module.split(struct.module))
  end

  defp rename_library_types(struct), do: struct

  defp do_process(struct, ["LibraryModule" | _]) do
    identifier = struct.identifier |> Atom.to_string()
    new_identifier = String.to_atom("prepend_name_" <> identifier)
    new_name = "PrependName" <> struct.name
    %{struct | identifier: new_identifier, name: new_name}
  end

  defp do_process(struct, _), do: struct
end