Add a SassScript repl.

lib/haml/exec.rb

@@ -185,9 +185,20 @@ END
                 'Line Comments. Emit comments in the generated CSS indicating the corresponding sass line.') do
           @options[:for_engine][:line_comments] = true
         end
+        opts.on('-i', '--interactive',
+                'Run an interactive SassScript shell.') do
+          @options[:interactive] = true
+        end
       end
 
       def process_result
+        if @options[:interactive]
+          require 'sass'
+          require 'sass/repl'
+          ::Sass::Repl.run
+          return
+        end
+
         super
         input = @options[:input]
         output = @options[:output]

lib/sass/repl.rb

@@ -0,0 +1,42 @@
+require 'readline'
+
+module Sass
+  module Repl
+    class << self
+      def run
+        environment = Environment.new
+        environment.set_var('important', Script::String.new('!important'))
+        loop do
+          unless text = Readline.readline('>> ')
+            puts
+            return
+          end
+
+          Readline::HISTORY << text
+          parse_input(environment, text)
+        end
+      end
+
+      private
+
+      def parse_input(environment, text)
+        case text
+        when Script::MATCH
+          name = $1
+          guarded = $2 == '||='
+          val = Script::Parser.parse($3)
+
+          unless guarded && environment.var(name)
+            environment.set_var(name, val.perform(environment))
+          end
+
+          p environment.var(name)
+        else
+          p Script::Parser.parse(text).perform(environment)
+        end
+      rescue Sass::SyntaxError => e
+        puts "SyntaxError: #{e.message}"
+      end
+    end
+  end
+end