Add rackup gem for visual spec checks

[larouxn]

Description

Adds rackup gem so we can perform visual spec checks. I think this used to be unnecessary when we had webrick built into Ruby but in modern Ruby trying bundle exec rackup simply errors out.

For a long time, rackup (the executable and implementation) was part of rack, and webrick was the default server, included with Ruby. It made it easy to run a Rack application without having to worry about the details of the server - great for documentation and demos.
https://github.com/rack/rackup/blob/f3fa1d6ada90e9e7aa1f712488ddde87ea2a2075/readme.md?plain=1#L47

rouge on  main [$] via 💎 v4.0.1 
❯ bundle exec rackup
bundler: failed to load command: rackup (/home/larouxn/.gem/ruby/4.0.1/bin/rackup)
/home/larouxn/.gem/ruby/4.0.1/gems/bundler-4.0.6/lib/bundler/rubygems_integration.rb:236:in 'block in Gem.replace_bin_path': can't find executable rackup for gem rack (Gem::Exception)
        from /home/larouxn/.rubies/ruby-4.0.1/lib/ruby/site_ruby/4.0.0/rubygems.rb:238:in 'Gem.find_and_activate_spec_for_exe'
        from /home/larouxn/.rubies/ruby-4.0.1/lib/ruby/site_ruby/4.0.0/rubygems.rb:283:in 'Gem.activate_and_load_bin_path'
        from /home/larouxn/.gem/ruby/4.0.1/bin/rackup:25:in '<top (required)>'
        from /home/larouxn/.gem/ruby/4.0.1/gems/bundler-4.0.6/lib/bundler/cli/exec.rb:61:in 'Kernel.load'
        from /home/larouxn/.gem/ruby/4.0.1/gems/bundler-4.0.6/lib/bundler/cli/exec.rb:61:in 'Bundler::CLI::Exec#kernel_load'
        from /home/larouxn/.gem/ruby/4.0.1/gems/bundler-4.0.6/lib/bundler/cli/exec.rb:24:in 'Bundler::CLI::Exec#run'
        from /home/larouxn/.gem/ruby/4.0.1/gems/bundler-4.0.6/lib/bundler/cli.rb:500:in 'Bundler::CLI#exec'
        from /home/larouxn/.gem/ruby/4.0.1/gems/bundler-4.0.6/lib/bundler/vendor/thor/lib/thor/command.rb:28:in 'Bundler::Thor::Command#run'
        from /home/larouxn/.gem/ruby/4.0.1/gems/bundler-4.0.6/lib/bundler/vendor/thor/lib/thor/invocation.rb:127:in 'Bundler::Thor::Invocation#invoke_command'
        from /home/larouxn/.gem/ruby/4.0.1/gems/bundler-4.0.6/lib/bundler/vendor/thor/lib/thor.rb:538:in 'Bundler::Thor.dispatch'
        from /home/larouxn/.gem/ruby/4.0.1/gems/bundler-4.0.6/lib/bundler/cli.rb:35:in 'Bundler::CLI.dispatch'
        from /home/larouxn/.gem/ruby/4.0.1/gems/bundler-4.0.6/lib/bundler/vendor/thor/lib/thor/base.rb:584:in 'Bundler::Thor::Base::ClassMethods#start'
        from /home/larouxn/.gem/ruby/4.0.1/gems/bundler-4.0.6/lib/bundler/cli.rb:29:in 'Bundler::CLI.start'
        from /home/larouxn/.gem/ruby/4.0.1/gems/bundler-4.0.6/exe/bundle:28:in 'block in <top (required)>'
        from /home/larouxn/.gem/ruby/4.0.1/gems/bundler-4.0.6/lib/bundler/friendly_errors.rb:118:in 'Bundler.with_friendly_errors'
        from /home/larouxn/.gem/ruby/4.0.1/gems/bundler-4.0.6/exe/bundle:20:in '<top (required)>'
        from /home/larouxn/.rubies/ruby-4.0.1/lib/ruby/site_ruby/4.0.0/rubygems.rb:304:in 'Kernel#load'
        from /home/larouxn/.rubies/ruby-4.0.1/lib/ruby/site_ruby/4.0.0/rubygems.rb:304:in 'Gem.activate_and_load_bin_path'
        from /home/larouxn/.gem/ruby/4.0.1/bin/bundle:25:in '<main>'

How?

Simply adds rackup to development gems.

Testing

[jneen]

Are there still docs that recommend rackup? We do have puma in the Gemfile, I've been meaning to replace those.

[larouxn]

Hmm, maybe I'm just running the wrong thing but I can't seem to get to the visual spec without using rackup. Tried running ruby spec/visual/app.rb as well but that fails at the Sinatra level.

As for the rackup messaging, the following message appears when running tests.

rouge on  main via 💎 v4.0.1 
❯ bundle exec rake

============
Run `rackup` and visit localhost:9292/:lexer_name to visually test a lexer.
============

Run options: --seed 26675

# Running:

............................................................

rouge/spec/visual_spec.rb

Lines 1 to 10 in 6a4ae1d

	# -*- coding: utf-8 -*- #
	# frozen_string_literal: true
	puts <<-MSG
	============
	Run `rackup` and visit localhost:9292/:lexer_name to visually test a lexer.
	============
	MSG

rackup appears in the README as well.

rouge/README.md

Lines 315 to 317 in 6a4ae1d

	To test a lexer visually, run `rackup` from the top-level working directory and
	you should have a web server running and ready to go. Visit
	<http://localhost:9292> to see the full list of Rouge's lexers.

[jneen]

I'll update those. bundle exec puma should do the trick.