From: Kouhei Sutou <kou@...>
Date: 2006-12-30T13:00:36+09:00
Subject: REXML 3.1.6 has XPath problems

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Hi,

I found some bugs of REXML 3.1.6 related XPath.

The following code raises an exception:

  require 'rexml/document'

  source = <<-XML
  <a>
    <b number='1' str='abc'>TEXT1</b>
    <c number='1'/>
    <c number='2' str='def'>
      <b number='3'/>
      <d number='1' str='abc'>TEXT2</d>
      <b number='2'><!--COMMENT--></b>
    </c>
  </a>
  XML
  doc = REXML::Document.new(source)

  predicate = "count(child::node()|following-sibling::node()|preceding-sibling::node())=0"
  p REXML::XPath.match(doc, "/descendant-or-self::node()[#{predicate}]")

The exception is the following:
  /usr/lib/ruby/1.8/rexml/xpath_parser.rb:335:in `expr': undefined method `children' for nil:NilClass (NoMethodError)
          from /usr/lib/ruby/1.8/rexml/xpath_parser.rb:334:in `each'
          from /usr/lib/ruby/1.8/rexml/xpath_parser.rb:334:in `expr'
          from /usr/lib/ruby/1.8/rexml/xpath_parser.rb:422:in `expr'
          from /usr/lib/ruby/1.8/rexml/xpath_parser.rb:421:in `expr'
          from /usr/lib/ruby/1.8/rexml/xpath_parser.rb:447:in `expr'
          from /usr/lib/ruby/1.8/rexml/xpath_parser.rb:445:in `collect'
          from /usr/lib/ruby/1.8/rexml/xpath_parser.rb:445:in `expr'
          from /usr/lib/ruby/1.8/rexml/encoding.rb:47:in `each_with_index'
           ... 14 levels...
          from /usr/lib/ruby/1.8/rexml/xpath_parser.rb:125:in `match'
          from /usr/lib/ruby/1.8/rexml/xpath_parser.rb:56:in `parse'
          from /usr/lib/ruby/1.8/rexml/xpath.rb:63:in `match'
          from rexml-3.1.6-xpath-bug.rb:21


I'll attach a patch of test case and fixing.

Thanks,
--
kou

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diff -ru rexml_3.1.6.orig/src/rexml/xpath_parser.rb rexml_3.1.6/src/rexml/xpath_parser.rb
--- rexml_3.1.6.orig/src/rexml/xpath_parser.rb	2006-11-28 22:54:57.000000000 +0900
+++ rexml_3.1.6/src/rexml/xpath_parser.rb	2006-12-30 12:55:45.000000000 +0900
@@ -351,7 +351,8 @@
         when :following_sibling
           #puts "FOLLOWING_SIBLING 1: nodeset = #{nodeset}"
           results = []
-          for node in nodeset
+          nodeset.each do |node|
+            next if node.parent.nil?
             all_siblings = node.parent.children
             current_index = all_siblings.index( node )
             following_siblings = all_siblings[ current_index+1 .. -1 ]
@@ -362,13 +363,14 @@
 
         when :preceding_sibling
           results = []
-          for node in nodeset
+          nodeset.each do |node|
+            next if node.parent.nil?
             all_siblings = node.parent.children
             current_index = all_siblings.index( node )
-            preceding_siblings = all_siblings[ 0 .. current_index-1 ].reverse
-            #results += expr( path_stack.dclone, preceding_siblings )
+            preceding_siblings = all_siblings[ 0, current_index ].reverse
+            results += preceding_siblings
           end
-          nodeset = preceding_siblings || []
+          nodeset = results
           node_types = ELEMENTS
 
         when :preceding
diff -ru rexml_3.1.6.orig/test/xpath_test_pred.rb rexml_3.1.6/test/xpath_test_pred.rb
--- rexml_3.1.6.orig/test/xpath_test_pred.rb	2006-11-28 22:54:56.000000000 +0900
+++ rexml_3.1.6/test/xpath_test_pred.rb	2006-12-30 12:53:44.000000000 +0900
@@ -54,4 +54,27 @@
     #puts path, @parser.parse( path ).inspect
     return m
   end
+
+  def test_get_no_siblings_terminal_nodes
+    source = <<-XML
+<a>
+  <b number='1' str='abc'>TEXT1</b>
+  <c number='1'/>
+  <c number='2' str='def'>
+    <b number='3'/>
+    <d number='1' str='abc'>TEXT2</d>
+    <b number='2'><!--COMMENT--></b>
+  </c>
+</a>
+XML
+    doc = REXML::Document.new(source)
+    predicate = "count(child::node()|" +
+                      "following-sibling::node()|" +
+                      "preceding-sibling::node())=0"
+    m = REXML::XPath.match(doc, "/descendant-or-self::node()[#{predicate}]")
+    assert_equal( [REXML::Text.new("TEXT1"),
+                   REXML::Text.new("TEXT2"),
+                   REXML::Comment.new("COMMENT")],
+                  m )
+  end
 end

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