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) request = ActionDispatch::Request.new env @app.call(env) rescue Exception => exception if request.show_exceptions? render_exception(request, exception) else raise exception end end private def render_exception(request, exception) backtrace_cleaner = request.get_header "action_dispatch.backtrace_cleaner" wrapper = ExceptionWrapper.new(backtrace_cleaner, exception) status = wrapper.status_code request.set_header "action_dispatch.exception", wrapper.exception request.set_header "action_dispatch.original_path", request.path_info request.path_info = "/#{status}" response = @exceptions_app.call(request.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