Ampersands in Sass selectors refer to the parent selectors.

git-svn-id: svn://hamptoncatlin.com/haml/trunk@420 7063305b-7217-0410-af8c-cdc13e5119b9

lib/sass.rb

@@ -142,6 +142,57 @@ $LOAD_PATH << dir unless $LOAD_PATH.include?(dir)
 #     #main pre {
 #       font-size: 3em; }
 #
+# === Referencing Parent Rules
+#
+# In addition to the default behavior of inserting the parent selector
+# as a CSS parent of the current selector
+# (e.g. above, "#main" is the parent of "p"),
+# you can have more fine-grained control over what's done with the parent selector
+# by using the ampersand character "&" in your selectors.
+#
+# The ampersand is automatically replaced by the parent selector,
+# instead of having it prepended.
+# This allows you to cleanly create pseudo-attributes:
+#
+#   a
+#     :font-weight bold
+#     :text-decoration none
+#     &:hover
+#       :text-decoration underline
+#     &:visited
+#       :font-weight normal
+#
+# Which would become:
+#
+#   a {
+#     font-weight: bold;
+#     text-decoration: none; }
+#     a:hover {
+#       text-decoration: underline; }
+#     a:visited {
+#       font-weight: normal; }
+#
+# It also allows you to add selectors at the base of the hierarchy,
+# which can be useuful for targeting certain styles to certain browsers:
+#
+#   #main
+#     :width 90%
+#     #sidebar
+#       :float left
+#       :margin-left 20%
+#       .ie6 &
+#         :margin-left 40%
+#
+# Which would become:
+#
+#   #main {
+#     width: 90%; }
+#     #main #sidebar {
+#       float: left;
+#       margin-left: 20%; }
+#       .ie6 #main #sidebar {
+#         margin-left: 40%; }
+#
 # === Attribute Namespaces
 #
 # CSS has quite a few attributes that are in "namespaces;"

lib/sass/tree/rule_node.rb

@@ -3,16 +3,26 @@ require 'sass/tree/attr_node'
 
 module Sass::Tree
   class RuleNode < ValueNode
+    # The character used to include the parent selector
+    PARENT = '&'
+
     alias_method :rule, :value
     alias_method :rule=, :value=
     
     def to_s(tabs, super_rules = nil)
       attributes = []
       sub_rules = []
+      refs_parent = self.rule.include? PARENT
       total_rule = if super_rules
         super_rules.split(/,\s*/).collect! do |s|
-          self.rule.split(/,\s*/).collect! {|r| "#{s} #{r}"}.join(", ")
+          if refs_parent
+            self.rule.gsub(PARENT, s)
+          else
+            self.rule.split(/,\s*/).collect {|r| "#{s} #{r}"}.join(", ")
+          end
         end.join(", ")
+      elsif refs_parent
+        raise Sass::SyntaxError.new("Base-level rules cannot contain the parent-selector-referencing character '#{PARENT}'", line)
       else
         self.rule
       end

test/sass/engine_test.rb

@@ -32,7 +32,8 @@ class SassEngineTest < Test::Unit::TestCase
     "a\n :b c" => "Illegal Indentation: Only two space characters are allowed as tabulation.",
     "a\n    :b c" => "Illegal Indentation: Only two space characters are allowed as tabulation.",
     "a\n  :b\n  !c = 3" => "Constants may only be declared at the root of a document.",
-    "!a = 1b + 2c" => "Incompatible units: b and c"
+    "!a = 1b + 2c" => "Incompatible units: b and c",
+    "& a\n  :b c" => "Base-level rules cannot contain the parent-selector-referencing character '&'"
   }
   
   def test_basic_render

test/sass/plugin_test.rb

@@ -8,7 +8,7 @@ RAILS_ENV  = 'testing'
 require 'sass/plugin'
 
 class SassPluginTest < Test::Unit::TestCase
-  @@templates = %w{ complex constants }
+  @@templates = %w{ complex constants parent_ref }
 
   def setup
     Sass::Plugin.options = {