Allow the use of custom SASS importers

[alem0lars]

By default SASS allows the definition of custom importers. Using this gem, you won't have that ability anymore because the importer choice is wired. This pull request allows the use of a custom importer (inheriting Sprockets::Sass::Importer) instead of the default one, if specified in the sass :importer configuration.

[petebrowne]

Thanks for this - can you add a test and I'll merge it in? I'm curious though, what's the use case? Wouldn't a custom importer defeat the purpose of using Sprockets::Sass?

[alem0lars]

The custom importer specified should be a Sprockets::Sass::Importer so it will have the basic features of the base importer and the custom behaviour..

There are many use cases for an importer, a common one is to interpret the path specified in @import, e.g.:

module SmartFS
  module Sass

    ##
    # Importer allowing smart files finding.
    #
    # Usage example in Middleman:
    #
    # - Edit the `config.rb` file:
    #
    #   set :sass, {:importer => SmartFS::Sass::Importer.new}
    #
    class Importer < Sprockets::Sass::Importer

      SMARTFS_REG = /@(?<what>[^:]+):(?<name>[^:]+)(?::(?<entry_point>[^:]+))?/

      def find_relative(uri, base, options, *args)
        middleman_app = options[:custom][:sprockets_context].app
        md = SMARTFS_REG.match(uri)
        unless md.nil? || md[:what].nil? || md[:name].nil?
          if md[:entry_point].nil?
            uri = middleman_app.c_css_path(md[:what], md[:name])
          else
            uri = middleman_app.c_css_path(md[:what], md[:name], md[:entry_point])
          end
        end
        super(uri, base, options, *args)
      end

      # Override because `super()` implementation is bad
      # (raises exception for `context` not found).
      def to_s
        self.class.name
      end

    end

  end
end

That importer (the one that I uses in my projects) will allow to make decisions about the physical path from the specified logical path.. For example one could use:

@import "@component:foobar"

to import the foobar component. In fact it underlies into c_css_path which will build the path using Middleman configuration variables.

Of course, this is just one opinionated use case. You can also define more sophisticated DSL-like syntaxes for importing stuff...

BTW, if you want to play with that importer this is the c_css_path definition: https://gist.github.com/alem0lars/d1cbf3bfa2ec52f83653

Sorry if I went OFT..

---

Coming back to our pull-request :smile:, to use that you need to configure SASS accordingly.. One example in Middleman would be:

set :sass, {:importer => SmartFS::Sass::Importer.new}

inside the config.rb file.

Of course the way to select the importer is not Middleman-specific: the code above just sets the Sass engine options, which is the standard way to configure Sass.

[petebrowne]

Ahh I see - that's a cool idea

[alem0lars]

I've added the test that ensures that the custom importer is used instead of the default one when specifying it in the SASS options.

BTW, you can selectively run that spec:

$ rspec -P spec/custom_importer_spec.rb

[petebrowne]

Thanks!

[alem0lars]

Could you maybe create a new gem so we can start using right now?

Thanks :smiley:

[petebrowne]

Release: http://rubygems.org/gems/sprockets-sass