Raises an exception if assets are missing from config.assets.precompile during development
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Assets Precompile Enforcer

This gem ensures that developers won't forget to add assets to config.assets.precompile while they are developing. An exception will be raised if you include an asset via javascript_include_tag or stylesheet_link_tag, and it doesn't match a filter in config.assets.precompile.


Add this line to your application's Gemfile, in the development group:

group :development do
  gem 'assets_precompile_enforcer'

And then execute:

$ bundle

Or install it yourself as:

$ gem install assets_precompile_enforcer


You will need to move your config.assets.precompile += ... setting into config/application.rb, instead of config/environments/production.rb. (This setting needs to be shared across development and production.)

You also need to add the following line to config/environments/development.rb:

# Forces included assets to be added to config.assets.precompile
config.assets.enforce_precompile = true

You can also specify a predicate to be tested when the check is about to be enforced:

# Forces included assets to be added to config.assets.precompile
config.assets.enforce_precompile = ->{ !Konacha || Konacha.config.blank? }

You will need to restart your Rails server whenever you make any changes to config.assets.precompile.


Whenever you call javascript_include_tag or stylesheet_link_tag for an asset that doesn't exist in the config.assets.precompile array, Rails will throw an error in your development environment:

<asset file> must be added to config.assets.precompile, otherwise it won't be precompiled for production!

Ignored assets

If you have any assets that you don't want to precompile for production, then you can ignore them:

config.assets.ignore_for_precompile = ['development_helpers.js']

Advanced Usage

To avoid restarting your server when you change config.assets.precompile, add the following lines to config/application.rb:

# Reload config/assets_precompile when changed
config.assets.original_precompile = config.assets.precompile.dup
config.to_prepare { load 'config/assets_precompile.rb' }
config.watchable_files << 'config/assets_precompile.rb'

Then move your config.assets.precompile settings to a new file at config/assets_precompile.rb:

# Precompile additional assets (application.js, application.css, and all non-JS/CSS are already added)
assets = Rails.application.config.assets
assets.precompile = assets.original_precompile + %w( extra_assets.js )

Now you will be able to make changes to config/assets_precompile.rb without needing to restart your server.

You can also configure a custom error message so that other developers know where to register their missing assets:

config.assets.precompile_error_message_proc = -> asset_file { "#{File.basename(asset_file)} must be added to `config/assets_precompile.rb`, otherwise it won't be precompiled for production!" }


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