Rails 4 Asset Pipeline: Asset missing fingerprint in asset_path from js

Question

I am deploying a Rails 4.0 application which includes HTML partial templates as assets for our front-end javascript framework. Although these templates are part of the asset pipeline and are properly precompiled, when I call asset_path from embedded ruby in our js files, it returns the path to our templates without the fingerprint.

I am quite certain that this is purely a Asset Pipeline question, but to give you a complete sense of our tech stack: We use Rails 4.0, Ruby 2.1, AngularJS for our front-end MVC framework, and AssetSync to synchronize our assets between Rails and our CDN.

An example of where this occurs (in a file included in app/assets/application.js.erb:

$routeProvider
    .when('/', {
      templateUrl: "<%= asset_path 'home.html' %>",
      controller: "HomeController"
    });

This works great locally, but as soon as config.assets.digest = true in production, the call to asset_path does not properly factor in the fingerprint. The templates are in the app/assets directory within a new subdirectory templates. So in the above example, the home.html asset is at app/assets/templates/home.html. Our javascript has itself been precompiled at that point, so I'm thinking that it might be an issue of which order the assets are precompiled in.

I've noticed a few issues on the Rails Github (1, 2, 3) and a couple of SO posts about fingerprints not being set properly (1, 2), but can't find anything about them not being included at all...

Any help or ideas that you can provide would be much appreciated.

Edit 4/15: forgot to include that the extensions on my application javascript file DOES include .erb (app/assets/application.js.erb). Thanks Alex for catching that. I've updated it above. Also, following instructions in this article on Heroku, I confirmed that running puts helper.asset_path("home.html") from within a Rails console running in production prints a properly fingerprinted URL for that asset.

Answer 1

This appears to be an issue with the AssetSync gem. I removed it, reconfigured the app so that Rails serves the assets, and the fingerprinting works fine.

If anyone else finds this question and is running into the same issue, I would recommend against using AssetSync. According to Heroku:

Many developers make use of Amazon’s S3 service for serving static assets that 
have been uploaded previously, either manually or by some form of build process.
Whilst this works, this is not recommended as S3 was designed as a file storage 
service and not for optimal delivery of files under load. Therefore, serving 
static assets from S3 is not recommended.

Amazon CloudFront is the preferred method of serving assets through a CDN, and is very easy to configure with a Rails app that serves its own static assets, accomplishing the same goals as AssetSync.

Answer 2

I'm pretty new to this stuff, but to get the asset_path to work, don't you need a .erb on the end of that file?

Check out the bottom of this article for more info:

https://devcenter.heroku.com/articles/rails-4-asset-pipeline

If it works in development, that may not help. There is a helpful section on debugging at the bottom of the article though.

Update

Here's another article that could help:

https://medium.com/self-directed-learning/9ba1f595102a

Flipping on this configuration in Heroku made some of my asset pipeline problems go away:

heroku labs:enable user-env-compile -a yourapp

Hope this helps!

Alex