Slow assets compilation in development mode

Question

I have a large rails app with hundreds of coffee script files.

Sometimes when I make a tiny change in a coffeescript file or I switch the branch the whole assets are

Answer 1

As others have pointed out, optimizing your assets is the #1 way to increase compilation speed (eliminate unnecessary files and pre-processors, import carefully, and use partials with caution). However, why are you turning config.assets.debug = false in development mode anyway? When it's false, sprockets will concatenate all your files together, and this can take quite a while if you have a large number of files.

Instead, turn config.assets.debug = true, so assets are compiled and cached on the first request. Sprockets sets a Cache-Control HTTP header to reduce request overhead on subsequent requests. The browser gets a 304 (Not Modified) response. See the Rails Asset Pipeline documentation.

Answer 2

Take a look at this middleware from the Discourse team. We've had great success with it in our rails 4 app -- took reload times down from a minute to 5 seconds in development.

Answer 3

It's a sad truth, but you don't. There is not a clean way to solve this.

However, there are some patterns you could follow to minimize your pain which if I understand correctly is having to wait a lot in development to see the changes.

As said these have been seen here1 and here2.

1. Take a look at item 2 from here1.
2. Break your assets in many files. This will imply in fewer lines being processed when changes occur.
3. Prefer css/js, they may not be as cool but require no compilation.
4. Find something interesting to do while assets precompile. It may lower productivity but sure kills the pain.