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# Copyright 2009 Canonical Ltd. This software is licensed under the
# GNU Affero General Public License version 3 (see the file LICENSE).
"""Validate XML documents against a schema."""
__all__ = [
'XMLValidator',
'RelaxNGValidator',
]
import os
from tempfile import NamedTemporaryFile
from canonical.launchpad.helpers import simple_popen2
class XMLValidator:
"""A validator for XML files against a schema."""
SCHEMA_ARGUMENT = 'schema'
def __init__(self, schema_filename):
"""Create a validator instance.
:param schema_filename: The name of a file containing the schema.
"""
self.schema_filename = schema_filename
self._errors = ''
def validate(self, xml):
"""Validate the string xml
:return: True, if xml is valid, else False.
"""
# XXX Abel Deuring, 2008-03-20
# The original implementation of the validation used the lxml
# package. Unfortunately, running lxml's Relax NG validator
# caused segfaults during PQM test runs, hence this class uses
# an external validator.
# Performance penalty of the external validator:
# Using the lxml validator, the tests in this module need ca.
# 3 seconds on a 2GHz Core2Duo laptop.
# If the xml data to be validated is passed to xmllint via
# canonical.launchpad.helpers.simple_popen2, the run time
# of the tests is 38..40 seconds; if the validation input
# is not passed via stdin but saved in a temporary file,
# the tests need 28..30 seconds.
xml_file = NamedTemporaryFile()
xml_file.write(xml)
xml_file.flush()
command = ['xmllint', '--noout', '--nonet',
'--%s' % self.SCHEMA_ARGUMENT,
self.schema_filename, xml_file.name]
local_catalog_path = os.path.abspath(
os.path.join(os.path.dirname(__file__), "tests",
"catalog", "catalog"))
catalogs = " ".join(
[local_catalog_path, "/etc/xml/catalog"])
env = {"XML_CATALOG_FILES": catalogs}
result = simple_popen2(command, '', env=env).strip()
# The output consists of lines describing possible errors; the
# last line is either "(file) fails to validate" or
# "(file) validates".
parts = result.rsplit('\n', 1)
if len(parts) > 1:
self._errors = parts[0]
status = parts[1]
else:
self._errors = ''
status = parts[0]
if status == xml_file.name + ' fails to validate':
return False
elif status == xml_file.name + ' validates':
return True
else:
raise AssertionError(
'Unexpected result of running xmllint: %s' % result)
@property
def error_log(self):
"""A string with the errors detected by the validator.
Each line contains one error; if the validation was successful,
error_log is the empty string.
"""
return self._errors
class RelaxNGValidator(XMLValidator):
"""A validator for Relax NG schemas."""
SCHEMA_ARGUMENT = 'relaxng'
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