Avoiding repetition of javascript version numbers in Rails manifest file - ruby-on-rails

Question

We require a number of different manifest files in order to only serve up the appropriate JS files for various functional areas of our site, however I'm currently having to replicate the JS file name and version number in each file so our manifests look like:
libs.js
//= require json2
//= require underscore-1.3.1
//= require jquery
//= require jquery-ui-1.8.17.custom.min
//= require jquery_ujs
//= require farbtastic-1.3u.gizmos
//= require bootstrap-2.0.1
//= require highstock-1.1.4.src
//= require exporting-1.1.4.src
//= require modernizr-2.5.3
//= require application
//= require validation
//= require navigation
//= require styles
libs-embedded.js
//= require json2
//= require jquery
//= require highstock-1.1.4.src
//= require exporting-1.1.4.src
I've tried to fix this by changing these manifest files with these .js.erb equivalents:
libs.js
<%= ManifestHelper.require_json2%>
<%= ManifestHelper.require_underscore%>
<%= ManifestHelper.require_jquery%>
<%= ManifestHelper.require_jquery_ui%>
<%= ManifestHelper.require_jquery_ujs%>
<%= ManifestHelper.require_farbtastic%>
<%= ManifestHelper.require_bootstrap%>
<%= ManifestHelper.require_highstock%>
<%= ManifestHelper.require_exporting%>
<%= ManifestHelper.require_modernizr%>
<%= ManifestHelper.require_application%>
<%= ManifestHelper.require_validation%>
<%= ManifestHelper.require_navigation%>
<%= ManifestHelper.require_styles%>
libs-embedded.js
<%= ManifestHelper.require_json2%>
<%= ManifestHelper.require_jquery%>
<%= ManifestHelper.require_highstock%>
<%= ManifestHelper.require_exporting%>
The ManifestHelper class includes methods such as:
def self.require_underscore
'//= require underscore-1.3.1'
end
This is intended to allow me to manage the JS file and version numbers in one place even though they are used in many manifest files.
However, when I try to do this, my libs.js files looks like:
//= require json2
//= require underscore-1.3.1
//= require jquery
//= require jquery-ui-1.8.17.custom.min
//= require jquery_ujs
//= require farbtastic-1.3u.gizmos
//= require bootstrap-2.0.1
//= require highstock-1.1.4
//= require exporting-1.1.4
//= require modernizr-2.5.3
//= require application
//= require validation
//= require styles
//= require navigation;
There are two problems with this. Firstly a semicolon is introduced for some reason. The second is that the generated .js file is not being populated with the concatenated js files defined in the //= requires directives.... It appears that although the .erb substitution is happening in the .js.erb file, it appears to be happening after the manifest file has read through the directives.
My question is... Can anyone suggest a way to fix this problem or suggest an alternate solution for me to stop replicating the js file and version numbers in each of my manifests...
Thanks,
Ian

Answer 1

One possible workaround would be to move shared javascript files into a "shared" subdirectory, then from your manifest file, use the require_directory directive to pull in the shared files.
//= require_directory shared
One bonus of this method is that you only have to drop a javascript file into the "shared" directory for it to be available for all the parent manifests that have the require_directory statement. No updating manifests or helper files.
Only potential issue there is that you can't control the order of the loading of the shared files if you have load order dependencies for those files. But that can be sorted out with a little more effort using an index manifest in the subdirectory to statically list the order of the files, then point to the index manifest from the parent manifest.

Answer 2

We managed to use this problem by using gems that wrap up the javascript libraries, for example we've been using the following gems:
gem 'jquery-rails'
gem 'jquery-ui-rails'
gem 'twitter-bootstrap-rails'
gem 'select2-rails'
gem 'underscore-rails'
gem 'underscore-string-rails'
This then allows you to include the relevant javascript library in your manifest using just the name of the library. For example: //= require select2 instead of //= require select2-x.y.z
Obviously the gems do many good things like managing the asset pipeline integration but we didn't have the library version numbers all over the place which I liked.