# Licensed under a 3-clause BSD style license - see LICENSE.rst

"""

Functions to do XML schema and DTD validation. At the moment, this

makes a subprocess call to xmllint. This could use a Python-based

library at some point in the future, if something appropriate could be

found.

"""

import os

import subprocess

def validate_schema(filename, schema_file):

"""

Validates an XML file against a schema or DTD.

Parameters

----------

filename : str

The path to the XML file to validate

schema_file : str

The path to the XML schema or DTD

Returns

-------

returncode, stdout, stderr : int, str, str

Returns the returncode from xmllint and the stdout and stderr

as strings

"""

base, ext = os.path.splitext(schema_file)

if ext == '.xsd':

schema_part = '--schema ' + schema_file

elif ext == '.dtd':

schema_part = '--dtdvalid ' + schema_file

else:

raise TypeError("schema_file must be a path to an XML Schema or DTD")

p = subprocess.Popen(

"xmllint --noout --nonet {} {}".format(schema_part, filename),

shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE)

stdout, stderr = p.communicate()

if p.returncode == 127:

raise OSError(

"xmllint not found, so can not validate schema")

elif p.returncode < 0:

from ..misc import signal_number_to_name

raise OSError(

"xmllint was terminated by signal '{0}'".format(

signal_number_to_name(-p.returncode)))

return p.returncode, stdout, stderr