Rails Engines: Common Assets

Question

I am writing a Rails 3.1 mounted engine that adds functions to the main application (i.e. it is not isolated). The JS engine depends on jQuery , jQueryUI , DataTables, and JSTree (among other libraries), so the engine manifest looks something like this:

// my_engine.js

//= require jquery
//= require jquery_ujs
//= require jquery-ui
//= require jstree_pre1.0_fix_1/jquery.jstree.js
//= require_tree .

Then I can conditionally load this file into the main application layout using:

<%= javascript_include_tag 'application' %>
<%= javascript_include_tag 'my_engine/my_engine' if user_logged_in? %>

However, if the main manifest of the application already includes one of the dependencies (most likely jQuery and jQuery_UJS), then these dependencies will be loaded twice. I will see something like:

<script src="/assets/jquery.js?body=1" type="text/javascript"></script>
<script src="/assets/jquery_ujs.js?body=1" type="text/javascript"></script>
...
<script src="/assets/application.js?body=1" type="text/javascript"></script>

<script src="/assets/jquery.js?body=1" type="text/javascript"></script>
<script src="/assets/jquery_ujs.js?body=1" type="text/javascript"></script>
<script src="/assets/jquery-ui.js?body=1" type="text/javascript"></script>
<script src="/assets/jstree_pre1.0_fix_1/jquery.jstree.js?body=1" type="text/javascript"></script>
...
<script src="/assets/cms/application.js?body=1" type="text/javascript"></script>

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Answer 1

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, my_engine.js :

//= require_tree .

:

application.js:

//= require jquery
//= require jquery_ujs
//= require_tree .

my_engine_requirements.js:

//= require jquery-ui
//= require jstree_pre1.0_fix_1/jquery.jstree.js
//= require my_engine/my_engine

application.html.erb:

<%= javascript_include_tag 'application' %>
<%= javascript_include_tag 'my_engine_requirements' if user_logged_in? %>

, , .