Error handler that generates error pages dynamically in Rails

application.rb

# config/application.rb
config.exceptions_app = ->(env) { ErrorsController.action(:show).call(env) }

errors_controller.rb

# app/controllers/errors_controller.rb
class ErrorsController < ActionController::Base
  layout 'application'

  rescue_from StandardError, with: :internal_server_error
  rescue_from ActiveRecord::RecordNotFound, ActionController::RoutingError, with: :not_found

  def not_found(exception = nil)
    render template: "errors/not_found", status: 404
  end

  def internal_server_error(exception = nil)
    render template: "errors/internal_server_error", status: 500
  end

  def show
    raise env["action_dispatch.exception"]
  end
end