xml module: Error w/ valid Xpath

[quocvu]

ISSUE TYPE

• Bug Report

COMPONENT NAME

XML Module

ANSIBLE VERSION

ansible 2.4.0.0
  config file = /Users/i857085/quoc/code/ansible/test_playbook/ansible.cfg
  configured module search path = [u'/Users/i857085/.ansible/plugins/modules', u'/usr/share/ansible/plugins/modules']
  ansible python module location = /Library/Python/2.7/site-packages/ansible
  executable location = /usr/local/bin/ansible
  python version = 2.7.10 (default, Feb  7 2017, 00:08:15) [GCC 4.2.1 Compatible Apple LLVM 8.0.0 (clang-800.0.34)]

CONFIGURATION

[defaults]

inventory = ./hosts
roles_path = ~/.ansible/roles:../
ansible_python_interpreter = python2

OS / ENVIRONMENT

OSX running ansible against a ArchLinux VM

SUMMARY

Getting invalid XPath

STEPS TO REPRODUCE

- name: Configure the number of virtual desktops
  xml:
    path: /home/{{ ansible_ssh_user }}/.config/openbox/rc.xml
    xpath: /openbox_config/desktops/number
    value: 3

I want to set the value of the xml tag to 3. XML file looks like this

<?xml version="1.0" encoding="UTF-8"?>

<!-- Do not edit this file, it will be overwritten on install.
        Copy the file to $HOME/.config/openbox/ instead. -->

<openbox_config xmlns="http://openbox.org/3.4/rc"
                xmlns:xi="http://www.w3.org/2001/XInclude">

<desktops>
  <!-- this stuff is only used at startup, pagers allow you to change them
       during a session

       these are default values to use when other ones are not already set
       by other applications, or saved in your session

       use obconf if you want to change these without having to log out
       and back in -->
  <number>4</number>
  <firstdesk>1</firstdesk>
  <names>
    <!-- set names up here if you want to, like this:
    <name>desktop 1</name>
    <name>desktop 2</name>
    -->
  </names>
  <popupTime>875</popupTime>
  <!-- The number of milliseconds to show the popup for when switching
       desktops.  Set this to 0 to disable the popup. -->
</desktops>
</openbox_config>

EXPECTED RESULTS

Expected the value changed from 4 to 3

ACTUAL RESULTS

getting this error

TASK [openbox-archlinux : Configure the number of virtual desktops] *************************
task path: /xyz/code/ansible/openbox-archlinux/tasks/main.yml:71
fatal: [172.28.128.3]: FAILED! => {"changed": false, "failed": true, "module_stderr": "Shared connection to 172.28.128.3 closed.\r\n", "module_stdout": "Traceback (most recent call last):\r\n  File \"/tmp/ansible_rh0r4yaw/ansible_module_xml.py\", line 546, in set_target_inner\r\n    changed = check_or_make_target(module, tree, xpath, namespaces)\r\n  File \"/tmp/ansible_rh0r4yaw/ansible_module_xml.py\", line 474, in check_or_make_target\r\n    changed = check_or_make_target(module, tree, inner_xpath, namespaces)\r\n  File \"/tmp/ansible_rh0r4yaw/ansible_module_xml.py\", line 474, in check_or_make_target\r\n    changed = check_or_make_target(module, tree, inner_xpath, namespaces)\r\n  File \"/tmp/ansible_rh0r4yaw/ansible_module_xml.py\", line 473, in check_or_make_target\r\n    if not is_node(tree, inner_xpath, namespaces):\r\n  File \"/tmp/ansible_rh0r4yaw/ansible_module_xml.py\", line 318, in is_node\r\n    if xpath_matches(tree, xpath, namespaces):\r\n  File \"/tmp/ansible_rh0r4yaw/ansible_module_xml.py\", line 342, in xpath_matches\r\n    if tree.xpath(xpath, namespaces=namespaces):\r\n  File \"src/lxml/lxml.etree.pyx\", line 2287, in lxml.etree._ElementTree.xpath (src/lxml/lxml.etree.c:68382)\r\n  File \"src/lxml/xpath.pxi\", line 359, in lxml.etree.XPathDocumentEvaluator.__call__ (src/lxml/lxml.etree.c:173282)\r\n  File \"src/lxml/xpath.pxi\", line 227, in lxml.etree._XPathEvaluatorBase._handle_result (src/lxml/lxml.etree.c:171653)\r\nlxml.etree.XPathEvalError: Invalid expression\r\n\r\nDuring handling of the above exception, another exception occurred:\r\n\r\nTraceback (most recent call last):\r\n  File \"/tmp/ansible_rh0r4yaw/ansible_module_xml.py\", line 853, in <module>\r\n    main()\r\n  File \"/tmp/ansible_rh0r4yaw/ansible_module_xml.py\", line 839, in main\r\n    set_target(module, doc, xpath, namespaces, attribute, value)\r\n  File \"/tmp/ansible_rh0r4yaw/ansible_module_xml.py\", line 573, in set_target\r\n    changed = set_target_inner(module, tree, xpath, namespaces, attribute, value)\r\n  File \"/tmp/ansible_rh0r4yaw/ansible_module_xml.py\", line 549, in set_target_inner\r\n    (xpath, e, etree.tostring(tree, pretty_print=True)), exception=traceback.format_exc(e))\r\n  File \"/usr/lib/python3.6/traceback.py\", line 163, in format_exc\r\n    return \"\".join(format_exception(*sys.exc_info(), limit=limit, chain=chain))\r\n  File \"/usr/lib/python3.6/traceback.py\", line 117, in format_exception\r\n    type(value), value, tb, limit=limit).format(chain=chain))\r\n  File \"/usr/lib/python3.6/traceback.py\", line 497, in __init__\r\n    capture_locals=capture_locals)\r\n  File \"/usr/lib/python3.6/traceback.py\", line 332, in extract\r\n    if limit >= 0:\r\nTypeError: '>=' not supported between instances of 'XPathEvalError' and 'int'\r\n", "msg": "MODULE FAILURE", "rc": 0}
	to retry, use: --limit @/xyz/code/ansible/test_playbook/playbook.retry

PLAY RECAP **********************************************************************************
172.28.128.3               : ok=7    changed=2    unreachable=0    failed=1

[ansibot]

cc @cmprescott @dagwieers @sm4rk0 @tbielawa
click here for bot help

[sm4rk0]

This is a common mistake. There's XML namespace set in your XML document: xmlns="http://openbox.org/3.4/rc" and you should use it in XPath. See the namespaces module argument and the last example in documentation.
Please close the issue if this comment helped.

[quocvu]

worked! Thanks @sm4rk0

[sm4rk0]

BTW, @dagwieers - this bug report reveals three things. (Should I open a new issue(s) for them?)

First is a need for specific error message in case of XPath exceptions due to the missing namespace argument (I'm adding this as an idea to the Module wiki).

Second is missing try block around a call to tree.xpath here:

def xpath_matches(tree, xpath, namespaces):
    """ Test if a node exists """
    if tree.xpath(xpath, namespaces=namespaces):
        return True
return False

Third is a bug in exception handling introduced by this commit prior to module upstreaming. This is the solution that should work (not tested).

Here's the formatted module_stdout from above (Actual results):

Traceback (most recent call last):
  File "/tmp/ansible_rh0r4yaw/ansible_module_xml.py", line 546, in set_target_inner
    changed = check_or_make_target(module, tree, xpath, namespaces)
  File "/tmp/ansible_rh0r4yaw/ansible_module_xml.py", line 474, in check_or_make_target
    changed = check_or_make_target(module, tree, inner_xpath, namespaces)
  File "/tmp/ansible_rh0r4yaw/ansible_module_xml.py", line 474, in check_or_make_target
    changed = check_or_make_target(module, tree, inner_xpath, namespaces)
  File "/tmp/ansible_rh0r4yaw/ansible_module_xml.py", line 473, in check_or_make_target
    if not is_node(tree, inner_xpath, namespaces):
  File "/tmp/ansible_rh0r4yaw/ansible_module_xml.py", line 318, in is_node
    if xpath_matches(tree, xpath, namespaces):
  File "/tmp/ansible_rh0r4yaw/ansible_module_xml.py", line 342, in xpath_matches
    if tree.xpath(xpath, namespaces=namespaces):
  File "src/lxml/lxml.etree.pyx", line 2287, in lxml.etree._ElementTree.xpath (src/lxml/lxml.etree.c:68382)
  File "src/lxml/xpath.pxi", line 359, in lxml.etree.XPathDocumentEvaluator.__call__ (src/lxml/lxml.etree.c:173282)
  File "src/lxml/xpath.pxi", line 227, in lxml.etree._XPathEvaluatorBase._handle_result (src/lxml/lxml.etree.c:171653)
lxml.etree.XPathEvalError: Invalid expression

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/tmp/ansible_rh0r4yaw/ansible_module_xml.py", line 853, in <module>
    main()
  File "/tmp/ansible_rh0r4yaw/ansible_module_xml.py", line 839, in main
    set_target(module, doc, xpath, namespaces, attribute, value)
  File "/tmp/ansible_rh0r4yaw/ansible_module_xml.py", line 573, in set_target
    changed = set_target_inner(module, tree, xpath, namespaces, attribute, value)
  File "/tmp/ansible_rh0r4yaw/ansible_module_xml.py", line 549, in set_target_inner
    (xpath, e, etree.tostring(tree, pretty_print=True)), exception=traceback.format_exc(e))
  File "/usr/lib/python3.6/traceback.py", line 163, in format_exc
    return "".join(format_exception(*sys.exc_info(), limit=limit, chain=chain))
  File "/usr/lib/python3.6/traceback.py", line 117, in format_exception
    type(value), value, tb, limit=limit).format(chain=chain))
  File "/usr/lib/python3.6/traceback.py", line 497, in __init__
    capture_locals=capture_locals)
  File "/usr/lib/python3.6/traceback.py", line 332, in extract
    if limit >= 0:
TypeError: '>=' not supported between instances of 'XPathEvalError' and 'int'

[dagwieers]

@sm4rk0 Please open issues for everything you consider needs a discussion, and PRs for everything you'd like to see changed. And thanks again for your help.