ExExport

This library provides an easy way to make barrel files in Elixir.

  A barrel is a way to rollup exports from several modules into a single convenient module.
  The barrel itself is a module file that re-exports selected exports of other modules.

Source: Barasat Gitbooks

I have grown used to having a lot of little files that get bundled up into a library (blame my time working in node/ES6 land). Because of the compiled nature of Elixir it seemed like this style of file structure should work without run time penalties.

This directive is an experiment to enable that. It allows me to build API barrels the same way I do in Javascript.

/lib api.ex actions/ welcome.ex farewell.ex

#api.ex
defmodule Api.Defs do
  @moduledoc """
  This module has to be compiled first so that the function is available in the module scope.
  """
  def exclude_list(), do: [exclude_from_function1: 1, exclude_from_function2: 1]
  def only_list(), do: [only_from_function1: 1, only_from_function2: 1]
end

defmodule API do
  require ExExport
  alias API.Actions.Welcome
  ExExport.export(Welcome)
  ExExport.export(API.Actions.Farewell)
  ExExport.export(API.Actions.AllButActionFromFunction,exclude: Api.Defs.exclude_list())
  ExExport.export(API.Actions.AllButAction,exclude: [all_but_action1: 1])
  ExExport.export(API.Actions.OnlySomeAction,only: [some_action1: 1])
  ExExport.export(API.Actions.OnlySomeActionFromFunction,only: Api.Defs.only_list())

end      

This adds defdelegate for all public methods in the referenced files. It filters out any methods that start with an underscore so that a method called _app_name or info would be auto excluded.

:only

This option allows you to set a list of specific functions/arity to include. If you define a function in a separate module you can use that to generate the list of function/arity that will be used.

:exclude

This includes all public functions except the ones matching the list of function/arity If you define a function in a separate module you can use that to generate the list of function/arity that will be used.

:expansion

This can be :manual or :macro. Default is :manual

• :macro - use Macro.expand. This seems to generate a compile time dependency
• :manual - uses custom code to figure out the alias resolution -which prevents the compile time dependency but can generate a warning - alias is unused because we are resolving it. You can get rid of the warning by changing to :macro, undoing the alias or adding warn: false to the alias

See the Output

In the configuration file for the environment you wish to render the data attributes, you can set the show_definitions to true. This will output the code that is being injected in a readable form. This can be useful if you get warnings like (Cannot match because already defined)

config :ex_export, :show_definitions, true

Installation

The package can be installed by adding ex_export to your list of dependencies in mix.exs:

def deps do
  [
    {:ex_export, "~> 0.8.2"}
  ]
end

Documentation can be generated with ExDoc and published on HexDocs. Once published, the docs can be found at https://hexdocs.pm/ex_export.