Sprockets Better Errors 
What
Errors, more of them, and better. For sprockets, specifically sprockets-rails < 2.1. The goal of this library is to make it painfully obvious when you've done something wrong with the rails asset pipeline. Like what?
Let's say you're referencing an asset in your view
<%= stylesheet_link_tag "search" %>This works in development but you'll find if you're precompiling your assets that it won't work in production. Why? By default sprockets is configured only to precompile application.css. Wouldn't it have been great if you could have been warned in development before you pushed to production and your site broke?
Asset filtered out and will not be served: add `config.assets.precompile += %w( search.css )` to `config/application.rb` and restart your server
That would be AMAZING! Well this gem adds these types of helpful errors!
Compatibility
Rails > 3.2.0 and < 4.0.6. See gemspec for details.
If you're using Rails 3.2 you will need to enable the Rails 4 asset pipeline in Rails 3.
Install
In your Gemfile add:
gem 'sprockets_better_errors'
Then run:
$ bundle install
And add this line to your config/environments/development.rb:
config.assets.raise_production_errors = true
Now develop with some sprockets super powers!
The Errors
We try to catch all mistakes but we're not perfect. Here's a list of the things we watch out for
Raise On Dev asset not in Precompile List
This is one of the most common asset errors I see at Heroku. We covered this error in the "Why" section above. Incase you're skipping around here's the run down:
Let's say you're referencing an asset in your view
<%= stylesheet_link_tag "search.css" %>This works in development but you'll find if you're precompiling your assets that it won't work in production. Why? By default sprockets is configured only to precompile application.css. Wouldn't it have been great if you could have been warned in development before you pushed to production and your site broke?
Asset filtered out and will not be served: add `config.assets.precompile += %w( search.css )` to `config/application.rb` and restart your server
Add this gem and you get that error.
Raise When Dependencies Improperly Used
This one may be a bit of an edge case for most people, but the difficulty in debugging (hours, days, weeks) is well worth the check.
If a dependency is used in an ERB asset that references another asset, it will not be updated when the reference asset is updated. The fix is to use //= depend_on or its cousin //= depend_on_asset however this is easy to forget. See rails/sprockets-rails#95 for more information.
Currently Rails/Sprockets hides this problem, and only surfaces it when the app is deployed with precompilation to production multiple times. We know that you will have this problem if you are referencing assets from within other assets and not declaring them as dependencies. This PR checks if you've declared a given file as a dependency before including it via asset_path. If not a helpful error is raised:
Asset depends on 'bootstrap.js' to generate properly but has not declared the dependency
Please add: `//= depend_on_asset "bootstrap.js"` to '/Users/schneems/Documents/projects/codetriage/app/assets/javascripts/application.js.erb'
Implementation is quite simple and limited to helper.rb, additional code is all around tests.
Upstream
Why not add this code upstream? I already tried, there are several PR awaiting merge. If you found this Gem useful maybe give them a :+1:.
- Raise On Dev asset not in Precompile list
- Raise on improper dependency use
- Bonus, not mine: Raise if ERB
Tests
Here's a one liner to running tests
$ export RAILS_VERSION=4.0.0; bundle update; bundle exec rake test
License
MIT