app-lib-fast_jsonapi-error_serializer.rb

module FastJsonapi
  module ErrorSerializer
    extend ActiveSupport::Concern

    included do
      include FastJsonapi::ObjectSerializer

      attr_accessor :with_root_key

      set_id :title

      def initialize(resource, options = {})
        super
        @with_root_key = options[:with_root_key] != false
      end

      def hash_for_one_record
        serialized_hash = super.dig(:data, :attributes)

        if with_root_key
          { errors: serialized_hash }
        else
          serialized_hash
        end
      end

      def hash_for_collection
        serialized_hash = super[:data]&.map { |err| err[:attributes] }

        if with_root_key
          { errors: serialized_hash }
        else
          serialized_hash
        end
      end
    end
  end
end

app-serializers-error_serializer.rb

class ErrorSerializer
  include FastJsonapi::ErrorSerializer

  attributes :title, :detail, :code, :status

  attribute :source do |object|
    object.serializer_source
  end
end

has_error_response.rb

module HasErrorResponse
  extend ActiveSupport::Concern

  included do
    rescue_from StandardError, with: :render_exception
    rescue_from ActiveRecord::RecordNotFound, with: :not_found
    rescue_from ActionController::RoutingError, with: :not_found
    rescue_from Pundit::NotAuthorizedError, with: :unauthorized
  end

  private

  def unauthorized(exception)
    render_exception(exception, code: :unauthorized)
  end

  def not_found(exception)
    render_exception(exception, code: :not_found)
  end

  def render_exception(exception, code: :internal_server_error)
    status = Rack::Utils.status_code(code).to_s
    object = OpenStruct.new(
      id: SecureRandom.uuid,
      title: I18n.t("#{status[0]}xx.title", scope: 'exceptions', default: :default),
      detail: exception.to_s.humanize,
      code: code,
      status: status
    )
    render json: ErrorSerializer.new(object), status: code
  end

  def render_errors(errors, code: :unprocessable_entity)
    objects = errors.as_json(full_messages: true).map do |attribute, messages|
      OpenStruct.new(
        id: SecureRandom.uuid,
        title: I18n.t(code, scope: 'errors', default: :default),
        detail: messages.to_sentence,
        code: attribute,
        status: Rack::Utils.status_code(code).to_s
      )
    end
    render json: ErrorSerializer.new(objects), status: code
  end
end