Missing assets in Rails 4.0 (part 2)

In addition to the asset path changes covered in part 1, there are some changes in how processed asset files are exposed to web clients.

In this case, the problem shows up with asset files that are referenced by name without the md5 fingerprint. Previously, plain-named asset files were also exposed to the webserver. Now they don’t seem to be.

The most likely culprit here are files referenced from within a CSS file, such as:

1src: font-url('custom-webfont.eot');
3background: url('background.png');

In this case, you’ll need to use the asset_path helper like so:

1src: url('<%= asset_path('custom-webfont.eot') %>');
3background: url('<%= asset_path('background.png') %>');

You may need to rename your css file to enable ERB parsing, eg: design.css becomes design.css.erb.

Another possibility are hard-coded asset references in your view templates somewhere. Once again, change such references to use the asset_path helper.


Missing assets in Rails 4.0 (part 1)

The asset pipeline was introduced in Rails 3.1. It continues to exist in Rails 4 and has seen a number of changes.

In one key change, Sprockets (the brains behind the asset pipeline) now looks in fewer places for asset files.

In Rails 3, Sprockets looked in app/assets, lib/assets, and vendor/assets for assets. Importantly, this applied not only to your main app, but also to any asset-providing gems, such as font-awesome-rails.

In Rails 4, Sprockets only looks in app/assets (both in your app and in gems). If you have any assets that aren’t working properly (most likely fonts, images, or CSS files not loading), first check for updated versions of any gems.

If it’s your own gem or a gem that hasn’t been updated, it may be as simple as moving lib/assets or vendor/assets to app/assets.