Sinatra asset pipeline, can't make it work - css

Question

I am using Sprockets with Sinatra, as suggested in Sinatra's page docs, but I can't make it work.
When I go to localhost:4567, the page loads correctly but with no styles. If I go to localhost:4567/assets/app.css, I get a not found error. I wonder what I am missing or what is wrong in the way I am using Sprockets?
This is my folder structure:
├── assets
│   ├── css
│   │   ├── app.css
│   │   ├── base.css
│   │   └── normalize.css
├── bin
│   └── app
├── lib
│   ├── app_assets.rb
│   └── main.rb
├── spec
│   ├── spec_helper.rb
│   └── main_spec.rb
├── views
│   └── index.erb
├── Gemfile
├── Gemfile.lock
├── Rakefile
├── .rspec
└── .ruby-version
The contents of app.css are:
//= require normalize
//= require base
The contents of app_assets.rb are:
module AppAssets
def self.environment root_path
environment = Sprockets::Environment.new root_path
environment.append_path './assets/css/'
environment
# get assets
get '/assets/*' do
env['PATH_INFO'].sub!('/assets', '')
settings.environment.call(env)
end
end
end
The contents of lib/main.rb are:
require 'sinatra'
require 'sprockets'
require 'app_assets'
class Main < Sinatra::Base
set :views, "#{settings.root}/../views"
get '/' do
erb :index
end
end
The file views/index.erb contains the line:
<link rel="stylesheet" href="assets/app.css">
And the contents of bin/app are:
#!/usr/bin/env ruby
$LOAD_PATH.unshift File.join(File.dirname(__FILE__), '..', 'lib')
require 'sinatra'
require 'sprockets'
require 'app_assets'
require 'main'
Main.run!
Which I run typing:
$ bin/app
Any help would be appreciated, I'm sure I made something wrong but I can't see what. Can anybody spot it?

Answer 1

The app_assets.rb file is the problem here. When you require this file inside another file, the methods you define inside this module are not automatically included. You need to explicitly include AppAssets wherever you need the self.environment method to exist.
The second issue here is that self.environment is not equivalent to settings.environment. If I understand correctly, what you're trying to do is define the asset routing whenever the module gets included. To achieve this one way is to use the included hook for modules. This hook gets run every time you include a module inside a context. If you use that, the code in app_assets.rb turns to:
module AppAssets
def self.included(klass)
environment = Sprockets::Environment.new klass.settings.root
# note the change to path. Since the file where this gets included
# is inside a sub-folder, we need to traverse to one level above.
environment.append_path '../assets/css/'
klass.set :environment, environment
klass.get '/assets/*' do
env['PATH_INFO'].sub!('/assets', '')
klass.settings.environment.call(env)
end
end
end
The klass argument to this hook is the class into which this module is included. In our case this is the Sinatra class you've described in main.rb. That file looks like:
class Main < Sinatra::Base
include AppAssets
# Same as what you have
end
There's a Sinatra Recipes article about using Sprockets with Sinatra: http://recipes.sinatrarb.com/p/asset_management/sprockets?#article