Implements outline parser

Per specs on http://www.w3.org/TR/CSS21/ui.html#propdef-outline and
http://www.w3.org/TR/CSS/

Author: zmoazeni

lib/csscss.rb

@@ -26,4 +26,5 @@
 require "csscss/parser/border_style"
 require "csscss/parser/border_side"
 require "csscss/parser/border"
+require "csscss/parser/outline"
 

lib/csscss/parser/outline.rb

@@ -0,0 +1,45 @@
+module Csscss
+  module Parser
+    module Outline
+      extend Parser::Base
+
+      class Parser < Parslet::Parser
+        include Color
+
+        rule(:outline_width) { BorderWidth::Parser.new.border_width_side }
+        rule(:outline_style) { BorderStyle::Parser.new.border_style_side }
+        rule(:outline_color) { BorderColor::Parser.new.border_color_side }
+
+        rule(:outline) {
+          (
+           symbol("inherit") >> eof | (
+             outline_width.maybe.as(:outline_width) >>
+             outline_style.maybe.as(:outline_style) >>
+             outline_color.maybe.as(:outline_color)
+           )
+          ).as(:outline)
+        }
+        root(:outline)
+      end
+
+      class Transformer < Parslet::Transform
+        extend Color::Transformer
+        extend Color::PlainColorValue
+
+        rule(outline: simple(:inherit)) {[]}
+
+        rule(outline: {
+          outline_width:simple(:width),
+          outline_style:simple(:style),
+          outline_color:simple(:color)
+        }) {
+          [].tap do |declarations|
+            declarations << Declaration.from_parser("outline-width", width) if width
+            declarations << Declaration.from_parser("outline-style", style) if style
+            declarations << Declaration.from_parser("outline-color", color) if color
+          end
+        }
+      end
+    end
+  end
+end

lib/csscss/redundancy_analyzer.rb

@@ -118,6 +118,7 @@ def shorthand_parser(property)
       when "border-width" then Parser::BorderWidth
       when "border-style" then Parser::BorderStyle
       when "border-color" then Parser::BorderColor
+      when "outline"      then Parser::Outline
       when "border-top", "border-right", "border-bottom", "border-left"
         Parser::BorderSide
       end

test/csscss/parser/outline_test.rb

@@ -0,0 +1,26 @@
+require "test_helper"
+
+module Csscss::Parser
+  module Outline
+    describe self do
+      include CommonParserTests
+
+      before do
+        @parser = Parser.new
+        @trans = Transformer.new
+      end
+
+      it "converts shorthand rules to longhand" do
+        trans("1px solid blue").must_equal([
+          dec("outline-width", "1px"),
+          dec("outline-style", "solid"),
+          dec("outline-color", "blue")
+        ])
+
+        trans("solid").must_equal([
+          dec("outline-style", "solid")
+        ])
+      end
+    end
+  end
+end