Layout filter for rake-pipeline

layout_filter.rb

# Support for rendering views in layout
# Example usage in Assetfile:
#
#  match "views/*.md" do
#    markdown
#    layout path: "app/views/layout.erb"
#    concat { |input| input.sub(%r{views/}, "").sub(/\.md/, ".html") }
#  end

require "rake-pipeline"
require "tilt"

module Rake
  class Pipeline
    module Layout
      class Filter < Rake::Pipeline::Filter
        attr_reader :options

        def initialize(options={}, &block)
          super(&block)

          @options = options
        end

        def generate_output(inputs, output)
          template = ::Tilt.new(options[:path])

          inputs.each do |input|
            output.write(template.render { input.read })
          end
        end
      end

      module Helpers
        def layout(*args, &block)
          filter(Rake::Pipeline::Layout::Filter, *args, &block)
        end
      end
    end
  end
end

Rake::Pipeline::DSL::PipelineDSL.send(:include, Rake::Pipeline::Layout::Helpers)