Automatic dependency detection

[tgecho]

So especially with the advent of the ExternalAssets branch, manually defining depends is getting even more old. I put together a proof of concept (https://gist.github.com/3915553) and it seems to be working out fairly well so far.

I'm not committed to the actual parsing method or the specific regexes, but they work for css/scss urls() and @imports.

Reading through the source, it seems that the biggest concern is in the performance of scanning all of the dependencies, especially as each of those can have dependencies and so on. I haven't put this through any serious paces yet, but personally I'm thinking it'll be worth it.

Thoughts?

[miracle2k]

This seems really cool. I'm not too worried about performance; it it really becomes a problem, various smartness could be imagined (say timestamp-based caching).

I would like to see an API where it's the filters that specify how the parsing is done. I believe it would make sense that multiple filters are used which each provide urls. Nested bundles also need to be supported. For example:

  Bundle('*.css', sass_stuff, filters='spritemapper')

This bundle would automatically have has dependencies then everything imported throughout sass, as well as the images to be sprited.

[tgecho]

I already rigged it up to cache based on filename/timestamp, and it checks all of the child dependencies each time as well.

I've definitely thought that something a little more sophisticated then a list of regexes would be good. The parsers don't have to be much more then a function that takes a filepath and return a list. One obvious missing parsing that can't be done with regex right now is one that can handle sass @imports without a file extension.

I wasn't really sure how/if filters could interact with the depends. So are you thinking that filters could basically return found dependancies alongside their usual output? Would it still be checked if it's a filter that doesn't always run? It doesn't really seem like a job for a filter to me, but I'm open.