[Ruby] Lack of `SCRIPT_NAME` Rack environment parameter causes crash

The Rack::URLMap class in (used by Rack::Builder, a commonly used utility) expects a SCRIPT_NAME parameter. When env['SCRIPT_NAME'] is nil, the following line causes a crash.

https://github.com/rack/rack/blob/98dbe17dd1e552783e056af15f4632ae4d462cc6/lib/rack/urlmap.rb#L73

undefined method `+' for nil:NilClass (NoMethodError)

I used the following middleware hack to temporarily fix it.

require 'rack'

class NginxPatcher
	def initialize(app)
		@app = app
	end

	def call(env)
		env[Rack::SCRIPT_NAME] ||= ''
		@app.call(env)
	end
end

In config.ru:

use NginxPatcher

I don't really care about the value of SCRIPT_NAME and I don't use it for anything. However, it would be nice if Unit would set this to an empty string at least so that the internals of Rack don't crash under normal use. SCRIPT_NAME is mentioned in the Rack spec, so it would be nice to have some kind of guarantees that the the spec is implemented at least to a point where it doesn't crash.

[travisbell]

Thanks for sharing @winduptoy, I've had this on my backlog to report for the past few months and just never got to it. 🙏🏼 Happy that someone wasn't as lazy as me! 😉

[hongzhidao]

Hi, @winduptoy @travisbell

Thanks for your reporting. Here's the patch of adding "SCRIPT_NAME" parameter.
https://gist.github.com/hongzhidao/1bbe0479a57377682a51dd3fabf7061e

Its value is set from the "script" option in the ruby application configuration.
Welcome to test.

[hongzhidao]

@winduptoy
It has been fixed with the commit: 0032543