How to access Parent imported functions from Module - testing

Question

I'm trying to create a test helper for testing an app that uses the Maru Framework. This is a simplified version of what I'm trying to achieve:
defmodule App.ExtendedMaru do
#moduledoc false
defmacro __using__(opts) do
quote do
use Maru.Test, unquote(opts)
end
end
def post_body(url, body) do
build_conn()
|> Plug.Conn.put_req_header("content-type", "application/json")
|> put_body_or_params(Poison.encode! body)
|> post(url)
end
end
The issues are with the build_conn/0 and post/2 functions. build_conn/0 is defined in Maru.Test and can thus be reached with import Maru.Test inside this module.
However, post/2 is a private function defined inside the __using__ macro for Maru.Test. So, it is present in the module that uses this one, but it's not available to post_body/2. I can't just use Maru.Test here as I'm required to pass the opts and haven't found a way to do so.
Is it possible to access the post/2 function that should be defined in the module that's including this one?
EDIT: How the code ended up:
defmodule Legacy.ExtendedMaru do
#moduledoc """
Adds a few extra function helpers for testing using the Maru framework. Use
it as you would Maru.Test, ie:
`use Legacy.ExtendedMaru, for: An.Api.Module`
"""
defmacro __using__(opts) do
quote do
use Maru.Test, unquote(opts)
unquote(add_post_body())
end
end
defp add_post_body() do
quote do
#doc """
Makes a POST request with the given body. Correctly encodes the body in the
requested format and sets Content-Type headers.
## Parameters
- url: The URL for the POST request
- body: The body to send on the request
- opts: For customizing function behaviour:
- format: What format to send the body in. Defaults to 'json'.
"""
#spec post_body(String.t, map(), keyword(String.t)) :: Plug.Conn.t
def post_body(url, body, opts \\ []) do
format = opts[:format] || "json"
build_conn()
|> add_content(body, format)
|> post(url)
end
def add_content(conn, body, "json") do
Plug.Conn.put_req_header(conn, "content-type", "application/json")
|> put_body_or_params(Poison.encode! body)
end
end
end
end

Answer 1

Your problem arises from two separate things:
The post_body method is private, so you can't call it outside of your Module.
The post_body method is not in the __using__ macro so it's not available to any of the other modules that use it.
There are two simple solutions to this:
Move the post_body method inside the __using__ macro. Once you do this, all modules that use it, will be able to call post_body except the original module.
(or) Make the post_body method public and call defdelegate on it inside __using__. This way you'll be able to call it in all modules including the original one.