fix all *-child pseudo selectors when used with a class and remove ne…

…ed for preprocessing the node tree

lib/nokogiri/css/node.rb

@@ -22,60 +22,10 @@ def accept visitor
       ###
       # Convert this CSS node to xpath with +prefix+ using +visitor+
       def to_xpath prefix = '//', visitor = XPathVisitor.new
-        self.preprocess!
         prefix = '.' if ALLOW_COMBINATOR_ON_SELF.include?(type) && value.first.nil?
         prefix + visitor.accept(self)
       end
 
-      # Preprocess this node tree
-      def preprocess!
-        ### Deal with nth-child
-        matches = find_by_type(
-          [:CONDITIONAL_SELECTOR,
-            [:ELEMENT_NAME],
-            [:PSEUDO_CLASS,
-              [:FUNCTION]
-            ]
-          ]
-        )
-        matches.each do |match|
-          if match.value[1].value[0].value[0] =~ /^nth-(last-)?child/
-            tag_name = match.value[0].value.first
-            match.value[0].value = ['*']
-            match.value[1] = Node.new(:COMBINATOR, [
-              match.value[1].value[0],
-              Node.new(:FUNCTION, ['self(', tag_name])
-            ])
-          end
-        end
-
-        ### Deal with first-child, last-child
-        matches = find_by_type(
-          [:CONDITIONAL_SELECTOR,
-            [:ELEMENT_NAME], [:PSEUDO_CLASS]
-        ])
-        matches.each do |match|
-          if ['first-child', 'last-child'].include?(match.value[1].value.first)
-            which = match.value[1].value.first.gsub(/-\w*$/, '')
-            tag_name = match.value[0].value.first
-            match.value[0].value = ['*']
-            match.value[1] = Node.new(:COMBINATOR, [
-              Node.new(:FUNCTION, ["#{which}("]),
-              Node.new(:FUNCTION, ['self(', tag_name])
-            ])
-          elsif 'only-child' == match.value[1].value.first
-            tag_name = match.value[0].value.first
-            match.value[0].value = ['*']
-            match.value[1] = Node.new(:COMBINATOR, [
-              Node.new(:FUNCTION, ["#{match.value[1].value.first}("]),
-              Node.new(:FUNCTION, ['self(', tag_name])
-            ])
-          end
-        end
-
-        self
-      end
-
       # Find a node by type using +types+
       def find_by_type types
         matches = []

lib/nokogiri/css/xpath_visitor.rb

@@ -2,7 +2,7 @@ module Nokogiri
   module CSS
     class XPathVisitor # :nodoc:
       def visit_function node
-        #  note that nth-child and nth-last-child are preprocessed in css/node.rb.
+
         msg = :"visit_function_#{node.value.first.gsub(/[(]/, '')}"
         return self.send(msg, node) if self.respond_to?(msg)
 
@@ -13,19 +13,31 @@ def visit_function node
           "self::#{node.value[1]}"
         when /^eq\(/
           "position() = #{node.value[1]}"
-        when /^(nth|nth-of-type|nth-child)\(/
+        when /^(nth|nth-of-type)\(/
           if node.value[1].is_a?(Nokogiri::CSS::Node) and node.value[1].type == :NTH
             nth(node.value[1])
           else
             "position() = #{node.value[1]}"
           end
-        when /^(nth-last-child|nth-last-of-type)\(/
+        when /^nth-child\(/
+          if node.value[1].is_a?(Nokogiri::CSS::Node) and node.value[1].type == :NTH
+            nth(node.value[1], :child => true)
+          else
+            "count(preceding-sibling::*) = #{node.value[1].to_i-1}"
+          end
+        when /^nth-last-of-type\(/
           if node.value[1].is_a?(Nokogiri::CSS::Node) and node.value[1].type == :NTH
             nth(node.value[1], :last => true)
           else
             index = node.value[1].to_i - 1
             index == 0 ? "position() = last()" : "position() = last() - #{index}"
           end
+        when /^nth-last-child\(/
+          if node.value[1].is_a?(Nokogiri::CSS::Node) and node.value[1].type == :NTH
+            nth(node.value[1], :last => true, :child => true)
+          else
+            "count(following-sbiling::*) = #{node.value[1].to_i-1}"
+          end
         when /^(first|first-of-type)\(/
           "position() = 1"
         when /^(last|last-of-type)\(/
@@ -105,11 +117,13 @@ def visit_pseudo_class node
           return self.send(msg, node) if self.respond_to?(msg)
 
           case node.value.first
-          when "first", "first-child" then "position() = 1"
-          when "last", "last-child" then "position() = last()"
+          when "first" then "position() = 1"
+          when "first-child" then "count(preceding-sibling::*) = 0"
+          when "last" then "position() = last()"
+          when "last-child" then "count(following-sibling::*) = 0"
           when "first-of-type" then "position() = 1"
           when "last-of-type" then "position() = last()"
-          when "only-child" then "last() = 1"
+          when "only-child" then "count(preceding-sibling::*) = 0 and count(following-sibling::*) = 0"
           when "only-of-type" then "last() = 1"
           when "empty" then "not(node())"
           when "parent" then "node()"
@@ -163,7 +177,11 @@ def nth node, options={}
         raise ArgumentError, "expected an+b node to contain 4 tokens, but is #{node.value.inspect}" unless node.value.size == 4
 
         a, b = read_a_and_positive_b node.value
-        position = options[:last] ? "(last()-position()+1)" : "position()"
+        position = if options[:child]
+          options[:last] ? "(count(following-sibling::*) + 1)" : "(count(preceding-sibling::*) + 1)"
+        else
+          options[:last] ? "(last()-position()+1)" : "position()"
+        end
 
         if (b == 0)
           return "(#{position} mod #{a}) = 0"

test/css/test_parser.rb

@@ -82,9 +82,9 @@ def test_includes
       end
 
       def test_function_with_arguments
-        assert_xpath  "//*[position() = 2 and self::a]",
+        assert_xpath  "//a[count(preceding-sibling::*) = 1]",
                       @parser.parse("a[2]")
-        assert_xpath  "//*[position() = 2 and self::a]",
+        assert_xpath  "//a[count(preceding-sibling::*) = 1]",
                       @parser.parse("a:nth-child(2)")
       end
 
@@ -174,15 +174,15 @@ def test_standard_nth_selectors
       end
 
       def test_nth_child_selectors
-        assert_xpath '//*[position() = 1 and self::a]',           @parser.parse('a:first-child')
-        assert_xpath '//*[position() = 99 and self::a]',          @parser.parse('a:nth-child(99)')
-        assert_xpath '//*[position() = last() and self::a]',      @parser.parse('a:last-child')
-        assert_xpath '//*[position() = last() and self::a]',      @parser.parse('a:nth-last-child(1)')
-        assert_xpath '//*[position() = last() - 98 and self::a]', @parser.parse('a:nth-last-child(99)')
+        assert_xpath '//a[count(preceding-sibling::*) = 0]',         @parser.parse('a:first-child')
+        assert_xpath '//a[count(preceding-sibling::*) = 98]',          @parser.parse('a:nth-child(99)')
+        assert_xpath '//a[count(following-sibling::*) = 0]',      @parser.parse('a:last-child')
+        assert_xpath '//a[count(following-sbiling::*) = 0]',      @parser.parse('a:nth-last-child(1)')
+        assert_xpath '//a[count(following-sbiling::*) = 98]', @parser.parse('a:nth-last-child(99)')
       end
 
       def test_miscellaneous_selectors
-        assert_xpath '//*[last() = 1 and self::a]',  @parser.parse('a:only-child')
+        assert_xpath '//a[count(preceding-sibling::*) = 0 and count(following-sibling::*) = 0]',  @parser.parse('a:only-child')
         assert_xpath '//a[last() = 1]', @parser.parse('a:only-of-type')
         assert_xpath '//a[not(node())]', @parser.parse('a:empty')
       end

test/css/test_xpath_visitor.rb

@@ -13,12 +13,12 @@ def test_not_simple_selector
       end
 
       def test_not_last_child
-        assert_xpath('//ol/*[not(position() = last())]',
+        assert_xpath('//ol/*[not(count(following-sibling::*) = 0)]',
           @parser.parse('ol > *:not(:last-child)'))
       end
 
       def test_not_only_child
-        assert_xpath('//ol/*[not(last() = 1)]',
+        assert_xpath('//ol/*[not(count(preceding-sibling::*) = 0 and count(following-sibling::*) = 0)]',
           @parser.parse('ol > *:not(:only-child)'))
       end