/usr/lib/python3/dist-packages/provisioningserver/utils/xpath.py is in python3-maas-provisioningserver 2.4.0~beta2-6865-gec43e47e6-0ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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# GNU Affero General Public License version 3 (see the file LICENSE).
"""XPath-related utilities."""
__all__ = [
'try_match_xpath',
]
import logging
from lxml import etree
def is_compiled_xpath(xpath):
"""Is `xpath` a compiled expression?"""
return isinstance(xpath, etree.XPath)
def is_compiled_doc(doc):
"""Is `doc` a compiled XPath document evaluator?"""
return isinstance(doc, etree.XPathDocumentEvaluator)
def match_xpath(xpath, doc):
"""Return a match of expression `xpath` against document `doc`.
:type xpath: Either `unicode` or `etree.XPath`
:type doc: Either `etree._ElementTree` or `etree.XPathDocumentEvaluator`
:rtype: bool
"""
is_xpath_compiled = is_compiled_xpath(xpath)
is_doc_compiled = is_compiled_doc(doc)
if is_xpath_compiled and is_doc_compiled:
return doc(xpath.path)
elif is_xpath_compiled:
return xpath(doc)
elif is_doc_compiled:
return doc(xpath)
else:
return doc.xpath(xpath)
def try_match_xpath(xpath, doc, logger=logging):
"""See if the XPath expression matches the given XML document.
Invalid XPath expressions are logged, and are returned as a
non-match.
:type xpath: Either `unicode` or `etree.XPath`
:type doc: Either `etree._ElementTree` or `etree.XPathDocumentEvaluator`
:rtype: bool
"""
try:
# Evaluating an XPath expression against a document with LXML
# can return a list or a string, and perhaps other types.
# Casting the return value into a boolean context appears to
# be the most reliable way of detecting a match.
return bool(match_xpath(xpath, doc))
except etree.XPathEvalError as error:
# Get a plaintext version of `xpath`.
expr = xpath.path if is_compiled_xpath(xpath) else xpath
logger.warning("Invalid expression '%s': %s", expr, str(error))
return False
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