Disable Sprockets asset caching in development

Question

I'm using Rails 3.2.13 and the Rails Asset Pipeline. I want to use the Asset Pipeline so I can use SASS and CoffeeScript and ERB for my assets and have the Pipeline automatically compile them, so I cannot turn off the pipeline in development. I am not precompiling assets in development ever and there is not even a public/assets/ directory.

However, when I make changes to an included file, such as to a _partial.html.erb file that is included (rendered) in a layout.html.erb file, without changing the file doing the including itself (in this example layout.html.erb), Sprockets doesn't detect the change and invalidate the cache, so I keep getting the same stale file. When I'm doing this in active development, I want to disable any caching of assets so I can get the changes on every request but I cannot figure out how to do this. I have set all of the following in my development.rb:

config.action_controller.perform_caching = false
config.action_dispatch.rack_cache =  nil
config.middleware.delete Rack::Cache
config.assets.debug = true
config.assets.compress = false
config.cache_classes = false

Still, even with this, files show up under tmp/cache/assets/ and tmp/cache/sass/ and changes are not available on future requests. Right now I have to manually delete those directories every time I want to see a change.

Unfortunately, the entire contents of the How Caching Works section of the RoR Guide for the Asset Pipeline is:

Sprockets uses the default Rails cache store to cache assets in development and production.

TODO: Add more about changing the default store.

So, how can I get Sprockets to compile assets on demand but not cache the results?

Answer 1

Here's the magic incantation:

config.assets.cache_store = :null_store  # Disables the Asset cache
config.sass.cache = false  # Disable the SASS compiler cache

The asset pipeline has it's own instance of a cache and setting config.assets.cache = false does nothing, so you have to set its cache to be the null_store to disable it.

Even then, the SASS compiler has it's own cache, and if you need to disable it, you have to disable it separately.