Rails asset pipeline, sub-URI deployment with path prefix, image_tag

Question

I have a Rails 3.1 application.

I am deploying it via passenger to a SubURI, not to URI root. For instance, the app root is actually accessed as http://somewhere.com/application .

I have a stylesheet.css.erb in my app using the asset pipeline, that sets a background-image with

<%= asset_path 'something.gif' %>

However, when I run rake assets:precompile, it precompiles this to /assets/something.gif, not /application/assets/something.gif -- because when I'm running the rake task from the command line, it doesn't yet know about the path prefix ("/application") that's going to be operative when running under Passenger at a SubURI.

What's the right way to handle this? Is there a way to tell the assets:precompile task to use a particular path prefix, because we know when precompiling that we're actually going to deploy to a path prefix?

• note: The path's generated by the actual live app, for instance stylesheet_link_tag 'application' in the layout, do generate properly with the path prefix. So the asset pipeline does respect the path prefix when it's operative. The problem is clearly that when I run assets:precompile, it's got no way of knowing what the ultimate prefix is going to be, the way I'm running it. How do I tell it?)

Answer 1

Okay, I guess maybe I'll accept @Tigraine's to give him the karma, as he LED me to the solution.

Just setting RAILS_RELATIVE_URL_ROOT is not enough however in current released Rails 3.1.3 (it might be in master) -- it won't do anything. You need to actually monkey patch Rails to add this feature.

What I actually ended up doing is a modified version of the solution given in one of the answers he pointed to. I use alias_method_chain to monkey patch copy-and-pasting as little of existing Rails logic as possible: https://gist.github.com/1595405

@Tigraine suggests there's a fix in master, I haven't confirmed this. If so, I have no idea what release of rails it's slated for (next 3.1.x, 3.2, even later?), or exactly what form it will take (RAILS_RELATIVE_URL_ROOT)? If anyone knows the answer to these, perhaps in the future when such a version is released, please add a comment or answer.

Answer 2

This has come up before: Seems to be a limitation in Sprockets that is now merged into master: https://github.com/rails/rails/pull/2977

I guess you need to set the RAILS_RELATIVE_URL_ROOT

Sources:

• Broken precompiled assets in Rails 3.1 when deploying to a sub-URI
• Rails 3.1 SASS asset helpers not not including RAILS_RELATIVE_URL_ROOT / relative_url_root