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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