I was checking out an old rails 3.2.3 project, and no asset pipeline manifests would render. When I inspected the rendered result for application.css in the browser, I saw the following:

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/*
 *= require_tree .
 *= require_self
*/

Symptoms

The asset pipeline just didn’t touch the file application.css, same for application.js. No asset pipeline config flag was able to fix this, also bundle update brought no improvement.

Solution

Back then we didn’t write any .ruby-version file or the like. So I was using the system default Ruby 2.2.2.

When I wrote a file pointing to Ruby 1.9.3 (to be used by rbenv), everything worked correctly again.

Discussion

Why there was no error message and the asset pipeline just refused to work is still a mystery to me. Just putting this out there, hoping to save the random googler some time!