Same Xpath returns different values in Centos, Ubuntu

[Lorenzo]

Note: I've opened the same request here: http://stackoverflow.com/questions/39899632/same-xpath-returns-different-values-on-centos-ubuntu

Given this simple XML:

<root>
    <outer>
        <inner>
            <el/>
        </inner>
        <inner>
            <el/>
        </inner>
    </outer>
</root>

This code:

from lxml import etree
r = etree.parse('foo.xml')
print 'One: ', r.xpath('.//el[2]')
print 'Two: ', r.xpath('(.//el)[2]')

Returns different output on different versions of Linux:

On Centos (python 2.7.5):

One: [<Element el at 0x25fdcf8>]
Two: [<Element el at 0x25fdcf8>]

Library versions:

Python : sys.version_info(major=2, minor=7, micro=5, releaselevel='final', serial=0)
lxml.etree : (3, 6, 4, 0)
libxml used : (2, 9, 1)
libxml compiled : (2, 9, 1)
libxslt used : (1, 1, 28)
libxslt compiled : (1, 1, 28)

On RedHat Enterprise 6.6 (python 2.7.11)

One: []
Two: [<Element el at 0x7fa27198cd40>]

Library versions:

Python : sys.version_info(major=2, minor=7, micro=11, releaselevel='final', serial=0)
lxml.etree : (3, 6, 0, 0)
libxml used : (2, 7, 6)
libxml compiled : (2, 7, 6)
libxslt used : (1, 1, 26)
libxslt compiled : (1, 1, 26)

On Debian and Ubuntu (python 2.7.9 and 2.7.12):

One: []
Two: [<Element el at 0x7f94ed6cf200>]

Debian library versions:

Python : sys.version_info(major=2, minor=7, micro=9, releaselevel='final', serial=0)
lxml.etree : (3, 6, 4, 0)
libxml used : (2, 9, 1)
libxml compiled : (2, 9, 1)
libxslt used : (1, 1, 28)
libxslt compiled : (1, 1, 28)

Ubuntu library versions:

Python : sys.version_info(major=2, minor=7, micro=12, releaselevel='final', serial=0)
lxml.etree : (3, 6, 4, 0)
libxml used : (2, 9, 3)
libxml compiled : (2, 9, 3)
libxslt used : (1, 1, 28)
libxslt compiled : (1, 1, 28)

[Lorenzo (lorenzo-grespan)]

A helpful comment from SO (http://stackoverflow.com/questions/39899632/same-xpath-returns-different-values-on-centos-ubuntu/39956501#39956501) suggests the issue is with Centos' libxml (2.9.1) which does not fix https://bugzilla.redhat.com/show_bug.cgi?id=1357971 and https://bugzilla.gnome.org/show_bug.cgi?id=695699.

I think this bug can be closed as it's related to libxml and not lxml.

[Lorenzo (lorenzo-grespan)]

Problem is with libxml, not lxml.