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hauleth.dev
1+++
2title = "Erlang in Mix"
3date = 2019-07-24T12:32:07+02:00
4draft = true
5+++
6
7Currently there are 3 main build tools in BEAM world:
8
9- Rebar3 - de facto standard in Erlang and other languages (with exception to
10 Elixir). Uses declarative `rebar.config` file (which is in `file:consult/1`
11 format) that can be then formatted via `rebar.config.script` Erlang script.
12- Mix - standard build tool in Elixir world. Uses imperative `mix.exs` file.
13- erlang.mk - GNU Make based tool. Uses it's own registry and is mostly known as
14 tool used by Cowboy.
15
16In this article I will cover only first two and their comparison when it comes
17to support building mostly Erlang projects (AFAIK `rebar3` do not have yet
18support for building Elixir projects, mostly because Elixir cannot be used as
19Erlang library).
20
21## Declarative vs imperative
22
23Accordingly to [Wikipedia][declarative programming]:
24
25> In computer science, declarative programming is a programming paradigm—a style
26> of building the structure and elements of computer programs—that expresses the
27> logic of a computation without describing its control flow.
28
29In other words, we only describe **what** without focusing on **how**. This mean
30that we have less direct control over our configuration while requiring less
31knowledge to configure properly.
32
33At the same time it is (in theory) more secure, as imagine that you would have
34dependency with such `mix.exs`:
35
36```elixir
37defmodule TotallySafeLibrary.Mixfile do
38 use Mix.Project
39
40 # HAHAHA I lied!!! Pwnd MF
41 File.rm_rf!(System.user_home())
42
43 # …
44end
45```
46
47I mean, this is still possible in Rebar via `rebar.config.script`, but it is
48much harder due to 2 reasons:
49
50- There is no such function like `File.rm_rf!/1` in Erlang, so the end user
51 would need to write their own.
52- It is much easier to spot additional file in the repo than review whole one
53 file.
54
55The same goes for `.app.src` file, which while having more "abstract" format
56than Mix's `application/0` function ends much simpler without all imperativeness
57brought by making configuration file executable script.
58
59## Tasks