Support prefixless CSS selectors for +, ~, and > (Issue #621)

lib/nokogiri/css/node.rb

@@ -1,6 +1,8 @@
 module Nokogiri
   module CSS
     class Node
+      ALLOW_COMBINATOR_ON_SELF = [:DIRECT_ADJACENT_SELECTOR, :FOLLOWING_SELECTOR, :CHILD_SELECTOR]
+
       # Get the type of this node
       attr_accessor :type
       # Get the value of this node
@@ -21,6 +23,7 @@ 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
 

lib/nokogiri/css/parser.y

@@ -9,12 +9,13 @@ rule
     : selector COMMA simple_selector_1toN {
         result = [val.first, val.last].flatten
       }
+    | prefixless_combinator_selector { result = val.flatten }
     | simple_selector_1toN { result = val.flatten }
     ;
   combinator
     : PLUS { result = :DIRECT_ADJACENT_SELECTOR }
     | GREATER { result = :CHILD_SELECTOR }
-    | TILDE { result = :PRECEDING_SELECTOR }
+    | TILDE { result = :FOLLOWING_SELECTOR }
     | S { result = :DESCENDANT_SELECTOR }
     | DOUBLESLASH { result = :DESCENDANT_SELECTOR }
     | SLASH { result = :CHILD_SELECTOR }
@@ -59,6 +60,11 @@ rule
         )
       }
     ;
+  prefixless_combinator_selector
+    : combinator simple_selector_1toN {
+        result = Node.new(val.first, [nil, val.last])
+      }
+    ;
   simple_selector_1toN
     : simple_selector combinator simple_selector_1toN {
         result = Node.new(val[1], [val.first, val.last])

lib/nokogiri/css/xpath_visitor.rb

@@ -126,13 +126,13 @@ def visit_class_condition node
       {
         'combinator'                => ' and ',
         'direct_adjacent_selector'  => "/following-sibling::*[1]/self::",
-        'preceding_selector'        => "/following-sibling::",
+        'following_selector'        => "/following-sibling::",
         'descendant_selector'       => '//',
         'child_selector'            => '/',
       }.each do |k,v|
         class_eval %{
           def visit_#{k} node
-            "\#{node.value.first.accept(self)}#{v}\#{node.value.last.accept(self)}"
+            "\#{node.value.first.accept(self) if node.value.first}#{v}\#{node.value.last.accept(self)}"
           end
         }
       end

test/css/test_parser.rb

@@ -214,6 +214,21 @@ def test_direct_preceding_selector
                       @parser.parse("E + F G")
       end
 
+      def test_prefixless_child_selector
+        assert_xpath("./a", @parser.parse('>a'))
+        assert_xpath("./a//b/i", @parser.parse('>a b>i'))
+      end
+
+      def test_prefixless_preceding_sibling_selector
+        assert_xpath("./following-sibling::a", @parser.parse('~a'))
+        assert_xpath("./following-sibling::a//b/following-sibling::i", @parser.parse('~a b~i'))
+      end
+
+      def test_prefixless_direct_adjacent_selector
+        assert_xpath("./following-sibling::*[1]/self::a", @parser.parse('+a'))
+        assert_xpath("./following-sibling::*[1]/self::a/following-sibling::*[1]/self::b", @parser.parse('+a+b'))
+      end
+
       def test_attribute
         assert_xpath  "//h1[@a = 'Tender Lovemaking']",
                       @parser.parse("h1[a='Tender Lovemaking']")