require 'action_dispatch/http/request' require 'action_dispatch/middleware/exception_wrapper' module ActionDispatch # This middleware rescues any exception returned by the application # and calls an exceptions app that will wrap it in a format for the end user. # # The exceptions app should be passed as parameter on initialization # of ShowExceptions. Every time there is an exception, ShowExceptions will # store the exception in env["action_dispatch.exception"], rewrite the # PATH_INFO to the exception status code and call the rack app. # # If the application returns a "X-Cascade" pass response, this middleware # will send an empty response as result with the correct status code. # If any exception happens inside the exceptions app, this middleware # catches the exceptions and returns a FAILSAFE_RESPONSE. class ShowExceptions FAILSAFE_RESPONSE = [500, { 'Content-Type' => 'text/plain' }, ["500 Internal Server Error\n" \ "If you are the administrator of this website, then please read this web " \ "application's log file and/or the web server's log file to find out what " \ "went wrong."]] def initialize(app, exceptions_app) @app = app @exceptions_app = exceptions_app end def call(env) begin response = @app.call(env) rescue Exception => exception raise exception if env['action_dispatch.show_exceptions'] == false end response || render_exception(env, exception) end private def render_exception(env, exception) wrapper = ExceptionWrapper.new(env, exception) status = wrapper.status_code env["action_dispatch.exception"] = wrapper.exception env["PATH_INFO"] = "/#{status}" response = @exceptions_app.call(env) response[1]['X-Cascade'] == 'pass' ? pass_response(status) : response rescue Exception => failsafe_error $stderr.puts "Error during failsafe response: #{failsafe_error}\n #{failsafe_error.backtrace * "\n "}" FAILSAFE_RESPONSE end def pass_response(status) [status, {"Content-Type" => "text/html; charset=#{Response.default_charset}", "Content-Length" => "0"}, []] end end end