Engine's assets with Rails 3.1

Question

How should one provide assets in an engine in Rails 3.1? Where should they be located and can they be included automatically?

(originally asked by Tomas Celizna)

Answer 1

The paths to the all the engines' assets folders are automatically loaded.

The assets themselves are not loaded by default. This is understandable as the loading is done with require_tree ., which loads all css/js from the current folder (i.e. the main application assets' folder) but doesn't say anything about the engines assets.

The easy solution is to ask the user to require the js/css in application.js/css or wherever else it is needed. As the paths are loaded correctly, the user only need to specify the name of your asset (I'd recommend using the name of your engine). Example:

Appended to main_app/app/assets/javascripts/application.js:

//= require your_engine_name

If you have split your js in different files, your file your_engine_name/app/assets/javascripts/your_engine_name.js could have the following:

//= require_tree .

This will load all js files in your_engine_name/app/assets/javascripts/, as the "." refers to the local folder (in this case the folder of your engine's javascripts).

Note that ActionView::Helpers::AssetTagHelper.register_javascript_expansion appears not to have any effect when config.use_sprockets is set. I hope they'll at least put a warning in that case.

If you have a rake task to install your engine, then you could do the append to application.js.

Another way for the user to include it is to insert <%= javascript_include_tag "your_engine_name" %> in the erb layout.

I don't think there is a way to have it inserted automatically