Lotus / JSONAPI / Reform Errors

controller.rb

ErrorsRepresenter.new(@operation.errors).to_json

error.rb

class Error
    include Virtus.value_object

    attribute :id
    attribute :status
    attribute :title
    attribute :detail

    def self.build_from_lotus(error)
      new(
        status: '400',
        title:  ErrorMessage.for(error),
        detail: ErrorMessage.for(error)
      )
    end
  end

  Errors = Struct.new(:errors)

  class ErrorRepresenter < Representable::Decorator
    include Representable::JSON

    property :id
    property :status
    property :title
    property :detail
  end

  class ErrorsRepresenter < Representable::Decorator
    include Representable::JSON

    collection :errors, extend: ErrorRepresenter
  end

error_message.rb

require 'active_support/core_ext/string/inflections'

class ErrorMessage

  DEFAULT_ERROR_MESSAGES = {
    acceptance:   ->(error) { "must be accepted" },
    confirmation: ->(error) { "doesn't match" },
    exclusion:    ->(error) { "shouldn't belong to #{ Array(error.expected).join(', ') }" },
    format:       ->(error) { "doesn't match expected format" },
    inclusion:    ->(error) { "isn't included" },
    presence:     ->(error) { "must be present" },
    size:         ->(error) { "doesn't match expected size" },
  }

  def self.for(error)
    new(error).message
  end

  def initialize(lotus_error)
    @lotus_error = lotus_error
  end

  def message
    "#{lotus_error.attribute_name.capitalize} #{DEFAULT_ERROR_MESSAGES.fetch(lotus_error.validation).call(lotus_error)}"
  end

  private

  attr_reader :lotus_error

end