xpath abbreviate: add a special case for only "//"

Author: kou

lib/rexml/parsers/xpathparser.rb

@@ -47,7 +47,6 @@ def abbreviate(path_or_parsed)
         end
         components = []
         component = nil
-        previous_op = nil
         while parsed.size > 0
           op = parsed.shift
           case op
@@ -119,10 +118,12 @@ def abbreviate(path_or_parsed)
             component << op.inspect
             component << ")"
           end
-          previous_op = op
         end
-        if components == [""]
+        case components
+        when [""]
           "/"
+        when ["", ""]
+          "//"
         else
           components.join("/")
         end

test/parser/test_xpath.rb

@@ -16,6 +16,11 @@ def test_document
                      abbreviate("/"))
       end
 
+      def test_descendant_or_self_only
+        assert_equal("//",
+                     abbreviate("/descendant-or-self::node()/"))
+      end
+
       def test_descendant_or_self_absolute
         assert_equal("//a/b",
                      abbreviate("/descendant-or-self::node()/a/b"))