How to read a YAML file into a Hash

Question

I have a requirement to read a YAML config file from disk into memory as a Hash in Crystal. (I am aware of this discussion on the topic in the mailing list, although I find it a bit confusing.)

The YAML file I am trying to read is a fairly simple config file:

---
:excludes:
  - Stage
  - Class
  - Anchor
  - Notify
  - Node
  - /::/
:only_include: []
:md5sums: false
:class_name: null
:catalog_file: null
:output_file: spec/classes/init_spec.rb
:compile_test: true
:setup: {}

A code example showing how to read a YAML config file from disk into a Hash using Crystal 0.25 would be very helpful.

Answer 1

Here's the best way to do it.

    require "yaml"

    class Config
      include YAML::Serializable

      @[YAML::Field(key: ":excludes")]
      property excludes : Array(String)

      @[YAML::Field(key: ":only_include")]
      property only_include : Array(String)

      @[YAML::Field(key: ":md5sums")]
      property md5sums : Bool

      @[YAML::Field(key: ":class_name")]
      property class_name : String?

      @[YAML::Field(key: ":catalog_file")]
      property catalog_file : String?

      @[YAML::Field(key: ":output_file")]
      property output_file : String

      @[YAML::Field(key: ":compile_test")]
      property compile_test : Bool

      @[YAML::Field(key: ":setup")]
      property setup : Hash(String, String)
    end

    yaml = <<-YAML
    :excludes:
      - Stage
      - Class
      - Anchor
      - Notify
      - Node
      - /::/
    :only_include: []
    :md5sums: false
    :class_name: null
    :catalog_file: null
    :output_file: spec/classes/init_spec.rb
    :compile_test: true
    :setup: {}
    YAML

    p Config.from_yaml(yaml)

Just note that YAML in Crystal currently does not support creating a Regex from YAML, so you'll probably want to do that after you parse it (it's a bit tricky with a converter).