Parse OpenAPI YAML files referencing other files

openapi.rb

require "psych"

class OpenAPI < Hash
  class << self
    def load_yaml_file(file)
      self[traverse(parse_yaml_file(file), File.dirname(file))]
    end

    private

    def parse_yaml_file(file)
      Psych.load_file(file, aliases: true)
    end

    def traverse(hsh, dir)
      hsh.each do |key, val|
        if key == "$ref" # Handle references to external files
          file = val.split("#").first
          hsh  = Dir.chdir(dir) do
            traverse(parse_yaml_file(file), File.dirname(file))
          end
        else
          case val
          when Hash
            hsh[key] = traverse(val, dir)
          when Array
            val.map! { |x| [Array, Hash].include?(x.class) ? traverse(x, dir) : x }
          end
        end
      end

      hsh
    end
  end
end