SprocketsUglifierWithSourceMaps

Create source maps when compressing assets in your Rails applications.

This gem uses Uglifier to create source maps for your concatenated javascripts in Rails. It is meant to be used as a replacement for javascript compressor.

Source maps are useful for debugging javascript and many errors monitoring services utilize them, for example Rollbar.

Rails versions supported: 4.2, 5. For Rails 3.2 see: https://github.com/leifcr/uglifier_with_source_maps

Installation

Add this line to your application's Gemfile:

gem 'sprockets_uglifier_with_source_maps'

And then execute:

$ bundle

Or install it yourself as:

$ gem install sprockets_uglifier_with_source_maps

Usage

In your Rails applications environment configuration:

config.assets.js_compressor = :uglifier_with_source_maps

If you need to pass options to uglifier:

config.assets.uglifier = {output: {beautify: true, indent_level: 2}, compress: {angular: true}}

Your assets will be built as normal, also maps and concatenated sources will be provided as well in public/assets/maps and public/assets/sources. These subdirs may be configured:

config.assets.sourcemaps_prefix = 'my_maps'
config.assets.uncompressed_prefix = 'my_sources'

Alternatively, sources can be embedded into sourcemaps' sourcesContent field:

config.assets.sourcemaps_embed_source = true

You can optionally skip gzipping your maps and sources:

config.assets.sourcemaps_gzip = false

By default maps and sources are defined relatively and will be fetched from the same domain your js file is served from. If you are using a CDN you may not want this - instead you might want to use a direct link to your site so you can more easily implement IP or Basic Auth protection:

# set to a url - js will be served from 'http://cdn.host.com' but source map links will use 'http://some.host.com/'

config.assets.sourcemaps_url_root = 'http://some.host.com/'

If you use CloudFront you might want to generate a signed url for these files that limits access based on IP address. You can do that by setting sourcemaps_url_root to a Proc and handling your URL signing there:

# using a Proc - see the AWS SDK docs for everything required to make this work
config.assets.sourcemaps_url_root = Proc.new { |file| MyApp.generate_a_signed_url_for file }

Example

$ rm -rf tmp/cache && rm -rf public/assets && DISABLE_SPRING=true RAILS_ENV=production bin/rake assets:precompile

$ tree public/assets
public/assets
├── application-f925f01bc55e9831029c1eb2c20ee889.js
├── maps
│   └── application-a3aff92c860f3876615c2d158f724865.js.map
└── sources
    └── application-73a007cf2d51c423a4420b649344b52e.js

$ tail -n1 public/assets/application-f925f01bc55e9831029c1eb2c20ee889.js
//# sourceMappingURL=/assets/maps/application-a3aff92c860f3876615c2d158f724865.js.map

$ head -c115 public/assets/maps/application-a3aff92c860f3876615c2d158f724865.js.map
{"version":3,"file":"application.js","sources":["/assets/sources/application-73a007cf2d51c423a4420b649344b52e.js"],

Troubleshooting

If sourcemaps are not generated, try rm -rf tmp/cache.

Contributing

1. Fork it
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -m 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create a new Pull Request