XPath Comparison Unexpected Error

[mirko314]

Hi again,

There seems to be a bug regarding boolean comparisons in the XPath evaluation.

Executing false()>=false() throws a NoMethodError (undefined method '>=' for false:FalseClass) Error.
Expected result: true

This leads to more crashes e.g when comparing empty-node sets with a boolean:
The expression /nonexistent>=false() throws an error as well.

Executing false()=false() however leads to the correct result true.

Complete Error:

Testing library: rexml , xpath: false()>=false()
Traceback (most recent call last):
        10: from /app/libraries/rexml/rexml.rb:17:in `<main>'
         9: from /usr/local/rvm/gems/ruby-2.6.3/gems/rexml-3.2.1/lib/rexml/xpath.rb:78:in `match'
         8: from /usr/local/rvm/gems/ruby-2.6.3/gems/rexml-3.2.1/lib/rexml/xpath_parser.rb:70:in `parse'
         7: from /usr/local/rvm/gems/ruby-2.6.3/gems/rexml-3.2.1/lib/rexml/xpath_parser.rb:133:in `match'
         6: from /usr/local/rvm/gems/ruby-2.6.3/gems/rexml-3.2.1/lib/rexml/xpath_parser.rb:345:in `expr'
         5: from /usr/local/rvm/gems/ruby-2.6.3/gems/rexml-3.2.1/lib/rexml/xpath_parser.rb:811:in `equality_relational_compare'
         4: from /usr/local/rvm/gems/ruby-2.6.3/gems/rexml-3.2.1/lib/rexml/syncenumerator.rb:27:in `each'
         3: from /usr/local/rvm/gems/ruby-2.6.3/gems/rexml-3.2.1/lib/rexml/syncenumerator.rb:27:in `times'
         2: from /usr/local/rvm/gems/ruby-2.6.3/gems/rexml-3.2.1/lib/rexml/syncenumerator.rb:28:in `block in each'
         1: from /usr/local/rvm/gems/ruby-2.6.3/gems/rexml-3.2.1/lib/rexml/xpath_parser.rb:814:in `block in equality_relational_compare'
/usr/local/rvm/gems/ruby-2.6.3/gems/rexml-3.2.1/lib/rexml/xpath_parser.rb:893:in `compare': undefined method `>=' for false:FalseClass (NoMethodError)

Furthermore we found that executing number(false()) results in NaN which is incorrect. Instead zero should be returned.

I hope this helps and best regards,
Mirko

[kou]

Could you show a Ruby script that reproduces this case?

[mirko314]

For sure:

require "rexml/document"
include REXML
string = <<EOF
  <?xml version="1.0"?>
  <bookstore>
  </bookstore>
EOF
doc = Document.new string
puts XPath.match( doc, "number(false())")
puts XPath.match( doc, "false()>=false()")

[kou]

Thanks.
I've fixed them.