Yaml for Elixir

How does it work?

This is a wrapper for yamerl - a native Erlang YAML parser which brings all of the functionalities to Elixir language.

Installation

Add Yaml Elixir as a dependency in your mix.exs file.

defp deps do
  [
     # ...
    { :yaml_elixir, "~> x.x.x" }, # where "x.x.x" equals version in mix.exs
  ]
end

You should also update your applications list to include Yaml Elixir:

def application do
  [
     applications: [
       # ...
       :yaml_elixir
     ]
  ]
end

Once you've done that, run mix deps.get in your command line to fetch the dependency.

Usage

With Yaml Elixir you have an access to two methods, one for parsing a string and an another one for parsing a file.

Run iex -S mix in your terminal to try how their works.

Parsing string

iex(1)>     yaml = """
...(1)>       a: a
...(1)>       b: 1
...(1)>       c: true
...(1)>       d: ~
...(1)>       e: nil
...(1)>     """
"  a: a\n  b: 1\n  c: true\n  d: ~\n  e: nil\n"
iex(2)> YamlElixir.read_from_string yaml
%{"a" => "a", "b" => 1, "c" => true, "d" => nil, "e" => "nil"}

Parsing file

iex(1)> path = File.cwd! |> Path.join("test/fixtures/flat.yml")
"/Users/squixy/Desktop/yaml-elixir/test/fixtures/flat.yml"
iex(2)> YamlElixir.read_from_file path
%{"a" => "a", "b" => 1, "c" => true, "d" => nil, "e" => []}

Support for atoms

By default, all map keys are processed as strings, as are all bareword or quoted values. If you would prefer to autodetect keys and values that begin with : as atoms, this can be accomplished by passing atoms: true as an option to any of the read_* functions.

iex(1)>     yaml = """
...(1)>       a: a
...(1)>       b: 1
...(1)>       c: true
...(1)>       d: ~
...(1)>       e: nil,
...(1)>       :f: :atom
...(1)>     """
"  a: a\n  b: 1\n  c: true\n  d: ~\n  e: nil\n"
iex(2)> YamlElixir.read_from_string yaml, atoms: true
%{:f => :atom, "a" => "a", "b" => 1, "c" => true, "d" => nil, "e" => "nil"}

Atoms are not garbage collected by BEAM, so be careful with this option, and don't use it with user-supplied input. One other caveat: if you enable autodetection of atoms, any string values entered (e.g., ":not_really_an_atom") will be converted to atoms, as well. If you only need to support a few atom values, you might be better off enabling yamerl's custom tag for atoms:

:yamerl_app.set_param(:node_mods, [:yamerl_node_erlang_atom])

and then using the somewhat inconvenient syntax for it:

atom_key: !<tag:yamerl,2012:atom> atom_value

Elixir Sigil

The YamlElixir.Sigil module provides the ~y sigil that can be useful for example for keeping short configurations or other inlined yaml.

import YamlElixir.Sigil

@config ~y"""
debug: false
port:  9200
files:
  - some/file.csv
  - another/file.csv
"""

Use the a sigil modifier to turn on atom values from yaml:

~y":answer: yes"a

You can find more examples in test directory.

Contribution

In case of any problems or suggestions do not hesitate and create a pull request.