+++ title = "Erlang in Mix" date = 2019-07-24T12:32:07+02:00 draft = true +++

Currently there are 3 main build tools in BEAM world:

• Rebar3 - de facto standard in Erlang and other languages (with exception to Elixir). Uses declarative rebar.config file (which is in file:consult/1 format) that can be then formatted via rebar.config.script Erlang script.
• Mix - standard build tool in Elixir world. Uses imperative mix.exs file.
• erlang.mk - GNU Make based tool. Uses it's own registry and is mostly known as tool used by Cowboy.

In this article I will cover only first two and their comparison when it comes to support building mostly Erlang projects (AFAIK rebar3 do not have yet support for building Elixir projects, mostly because Elixir cannot be used as Erlang library).

Declarative vs imperative#

Accordingly to [Wikipedia][declarative programming]:

In computer science, declarative programming is a programming paradigm—a style of building the structure and elements of computer programs—that expresses the logic of a computation without describing its control flow.

In other words, we only describe what without focusing on how. This mean that we have less direct control over our configuration while requiring less knowledge to configure properly.

At the same time it is (in theory) more secure, as imagine that you would have dependency with such mix.exs:

defmodule TotallySafeLibrary.Mixfile do
  use Mix.Project

  # HAHAHA I lied!!! Pwnd MF
  File.rm_rf!(System.user_home())

  # …
end

I mean, this is still possible in Rebar via rebar.config.script, but it is much harder due to 2 reasons:

• There is no such function like File.rm_rf!/1 in Erlang, so the end user would need to write their own.
• It is much easier to spot additional file in the repo than review whole one file.

The same goes for .app.src file, which while having more "abstract" format than Mix's application/0 function ends much simpler without all imperativeness brought by making configuration file executable script.

Tasks#