# !/usr/bin/env python
#
# xml.py
"""
Functions and classes for handling XML files.
"""
#
# Copyright © 2019-2020 Dominic Davis-Foster <dominic@davis-foster.co.uk>
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU Lesser General Public License as published by
# the Free Software Foundation; either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
# MA 02110-1301, USA.
#
# stdlib
import pathlib
from abc import ABC, abstractmethod
from typing import Optional
# 3rd party
import lxml # type: ignore
from domdf_python_tools.typing import PathLike
from lxml import etree, objectify
from lxml.etree import _ElementTree # type: ignore
from lxml.objectify import ObjectifiedElement # type: ignore
__all__ = ["get_validated_tree", "XMLFileMixin"]
[docs]def get_validated_tree(xml_file: PathLike, schema_file: Optional[PathLike] = None) -> _ElementTree:
"""
Returns a validated lxml objectify from the given XML file, validated against the schema file.
:param xml_file: The XML file to validate.
:param schema_file: The schema file to validate against.
:returns: An lxml ElementTree object. When .getroot() us called on the tree the root will be an instance of
:class:`lxml.objectify.ObjectifiedElement`.
"""
if not isinstance(xml_file, pathlib.Path):
xml_file = pathlib.Path(xml_file)
if not xml_file.is_file():
raise FileNotFoundError(f"XML file '{xml_file}' not found.")
schema: Optional[etree.XMLSchema] = None
if schema_file is not None:
if not isinstance(schema_file, pathlib.Path):
schema_file = pathlib.Path(schema_file)
if not schema_file.is_file():
raise FileNotFoundError(f"XML schema '{schema_file}' not found.")
schema = etree.XMLSchema(etree.parse(str(schema_file)))
parser = objectify.makeparser(schema=schema)
tree: _ElementTree = objectify.parse(str(xml_file), parser=parser)
if schema:
assert schema.validate(tree)
return tree
[docs]class XMLFileMixin(ABC):
"""
ABC mixin to provide a function for instantiating the class from an XML file.
"""
_schema: Optional[str] = None
[docs] @classmethod
def from_xml_file(cls, filename: PathLike):
"""
Generate an instance of this class by parsing an from an XML file.
:param filename: The filename of the XML file.
"""
tree = get_validated_tree(filename, cls._schema)
root: ObjectifiedElement = tree.getroot()
return cls.from_xml(root)
[docs] @classmethod
@abstractmethod
def from_xml(cls, element: lxml.objectify.ObjectifiedElement):
"""
Construct an object from an XML element.
"""