Compass + Multiple Images Directories

compass.md

I have the following in my project:

  // in app/stylesheets/foo.scss:
  .foo {
    // foo.png is at app/images/foo.png
    background-image: image-url("foo.png");
  }

  // in vendor/stylesheets/bar.scss:
  .bar {
    // bar.png is at vendor/images/bar.png
    background-image: image-url("bar.png");
  }

If I try to compile both of those SCSS files, Compass will complain:

WARNING: 'foo.png' was not found (or cannot be read) in ./images WARNING: 'bar.png' was not found (or cannot be read) in ./images

The problem is that Compass assumes a single images_dir. There are a few solutions to this:

1. I set images_dir to . and use the relative paths (e.g. image-url("app/images/foo.png") in my stylesheets. That works great for my stylesheets, but it means I have to edit things in vendor to suit the structure of my application. Not nice.
2. I change Compass to support multiple image_dirs. This is certainly possible. I imagine they would work like load paths, so I could put images_dirs = [ "app/images", "vendor/images" ] and could thus override a vendor image with one of my own.
3. I change Compass to support per-compilation configuration. I could have project-wide defaults in the Compass configuration file. Then I would do something like

Compass.compile('vendor/stylehseets/bar.scss', :images_dir => 'vendor/images')

I'm equally happy with #2 and #3. I'd love to hear people's thoughts.

(NB: though this project is structured much like a Rails project, it's not Rails. Indeed, there's no Ruby server at all. It's a static site generator using rake-pipeline)

@chriseppstein suggested instead doing something like what sprockets-sass does. That is, monkey-patching the Functions::Urls methods to work with my environment. This is a proven method, but I believe the fact that that exists (and in several other repositories as well) shows that this is something that people would appreciate being able to do in Compass.

I've been working on this here https://github.com/buhrmi/compass/tree/multiple_image_dirs