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# encoding: utf-8
"""
Provides a wrapper around lxml that enables declarative definition of custom
element classes.
"""
from __future__ import absolute_import
from lxml import etree
import re
from . import OxmlElement
from ..compat import Unicode
from .exceptions import InvalidXmlError
from .ns import NamespacePrefixedTag, nsmap, qn
from ..shared import lazyproperty
def serialize_for_reading(element):
"""
Serialize *element* to human-readable XML suitable for tests. No XML
declaration.
"""
xml = etree.tostring(element, encoding='unicode', pretty_print=True)
return XmlString(xml)
class XmlString(Unicode):
"""
Provides string comparison override suitable for serialized XML that is
useful for tests.
"""
# ' <w:xyz xmlns:a="http://ns/decl/a" attr_name="val">text</w:xyz>'
# | | || |
# +----------+------------------------------------------++-----------+
# front attrs | text
# close
_xml_elm_line_patt = re.compile(
'( *</?[\w:]+)(.*?)(/?>)([^<]*</[\w:]+>)?$'
)
def __eq__(self, other):
lines = self.splitlines()
lines_other = other.splitlines()
if len(lines) != len(lines_other):
return False
for line, line_other in zip(lines, lines_other):
if not self._eq_elm_strs(line, line_other):
return False
return True
def __ne__(self, other):
return not self.__eq__(other)
def _attr_seq(self, attrs):
"""
Return a sequence of attribute strings parsed from *attrs*. Each
attribute string is stripped of whitespace on both ends.
"""
attrs = attrs.strip()
attr_lst = attrs.split()
return sorted(attr_lst)
def _eq_elm_strs(self, line, line_2):
"""
Return True if the element in *line_2* is XML equivalent to the
element in *line*.
"""
front, attrs, close, text = self._parse_line(line)
front_2, attrs_2, close_2, text_2 = self._parse_line(line_2)
if front != front_2:
return False
if self._attr_seq(attrs) != self._attr_seq(attrs_2):
return False
if close != close_2:
return False
if text != text_2:
return False
return True
@classmethod
def _parse_line(cls, line):
"""
Return front, attrs, close, text 4-tuple result of parsing XML element
string *line*.
"""
match = cls._xml_elm_line_patt.match(line)
front, attrs, close, text = [match.group(n) for n in range(1, 5)]
return front, attrs, close, text
class MetaOxmlElement(type):
"""
Metaclass for BaseOxmlElement
"""
def __init__(cls, clsname, bases, clsdict):
dispatchable = (
OneAndOnlyOne, OneOrMore, OptionalAttribute, RequiredAttribute,
ZeroOrMore, ZeroOrOne, ZeroOrOneChoice
)
for key, value in clsdict.items():
if isinstance(value, dispatchable):
value.populate_class_members(cls, key)
class BaseAttribute(object):
"""
Base class for OptionalAttribute and RequiredAttribute, providing common
methods.
"""
def __init__(self, attr_name, simple_type):
super(BaseAttribute, self).__init__()
self._attr_name = attr_name
self._simple_type = simple_type
def populate_class_members(self, element_cls, prop_name):
"""
Add the appropriate methods to *element_cls*.
"""
self._element_cls = element_cls
self._prop_name = prop_name
self._add_attr_property()
def _add_attr_property(self):
"""
Add a read/write ``{prop_name}`` property to the element class that
returns the interpreted value of this attribute on access and changes
the attribute value to its ST_* counterpart on assignment.
"""
property_ = property(self._getter, self._setter, None)
# assign unconditionally to overwrite element name definition
setattr(self._element_cls, self._prop_name, property_)
@property
def _clark_name(self):
if ':' in self._attr_name:
return qn(self._attr_name)
return self._attr_name
class OptionalAttribute(BaseAttribute):
"""
Defines an optional attribute on a custom element class. An optional
attribute returns a default value when not present for reading. When
assigned |None|, the attribute is removed.
"""
def __init__(self, attr_name, simple_type, default=None):
super(OptionalAttribute, self).__init__(attr_name, simple_type)
self._default = default
@property
def _getter(self):
"""
Return a function object suitable for the "get" side of the attribute
property descriptor.
"""
def get_attr_value(obj):
attr_str_value = obj.get(self._clark_name)
if attr_str_value is None:
return self._default
return self._simple_type.from_xml(attr_str_value)
get_attr_value.__doc__ = self._docstring
return get_attr_value
@property
def _docstring(self):
"""
Return the string to use as the ``__doc__`` attribute of the property
for this attribute.
"""
return (
'%s type-converted value of ``%s`` attribute, or |None| (or spec'
'ified default value) if not present. Assigning the default valu'
'e causes the attribute to be removed from the element.' %
(self._simple_type.__name__, self._attr_name)
)
@property
def _setter(self):
"""
Return a function object suitable for the "set" side of the attribute
property descriptor.
"""
def set_attr_value(obj, value):
if value is None or value == self._default:
if self._clark_name in obj.attrib:
del obj.attrib[self._clark_name]
return
str_value = self._simple_type.to_xml(value)
obj.set(self._clark_name, str_value)
return set_attr_value
class RequiredAttribute(BaseAttribute):
"""
Defines a required attribute on a custom element class. A required
attribute is assumed to be present for reading, so does not have
a default value; its actual value is always used. If missing on read,
an |InvalidXmlError| is raised. It also does not remove the attribute if
|None| is assigned. Assigning |None| raises |TypeError| or |ValueError|,
depending on the simple type of the attribute.
"""
@property
def _getter(self):
"""
Return a function object suitable for the "get" side of the attribute
property descriptor.
"""
def get_attr_value(obj):
attr_str_value = obj.get(self._clark_name)
if attr_str_value is None:
raise InvalidXmlError(
"required '%s' attribute not present on element %s" %
(self._attr_name, obj.tag)
)
return self._simple_type.from_xml(attr_str_value)
get_attr_value.__doc__ = self._docstring
return get_attr_value
@property
def _docstring(self):
"""
Return the string to use as the ``__doc__`` attribute of the property
for this attribute.
"""
return (
'%s type-converted value of ``%s`` attribute.' %
(self._simple_type.__name__, self._attr_name)
)
@property
def _setter(self):
"""
Return a function object suitable for the "set" side of the attribute
property descriptor.
"""
def set_attr_value(obj, value):
str_value = self._simple_type.to_xml(value)
obj.set(self._clark_name, str_value)
return set_attr_value
class _BaseChildElement(object):
"""
Base class for the child element classes corresponding to varying
cardinalities, such as ZeroOrOne and ZeroOrMore.
"""
def __init__(self, nsptagname, successors=()):
super(_BaseChildElement, self).__init__()
self._nsptagname = nsptagname
self._successors = successors
def populate_class_members(self, element_cls, prop_name):
"""
Baseline behavior for adding the appropriate methods to
*element_cls*.
"""
self._element_cls = element_cls
self._prop_name = prop_name
def _add_adder(self):
"""
Add an ``_add_x()`` method to the element class for this child
element.
"""
def _add_child(obj, **attrs):
new_method = getattr(obj, self._new_method_name)
child = new_method()
for key, value in attrs.items():
setattr(child, key, value)
insert_method = getattr(obj, self._insert_method_name)
insert_method(child)
return child
_add_child.__doc__ = (
'Add a new ``<%s>`` child element unconditionally, inserted in t'
'he correct sequence.' % self._nsptagname
)
self._add_to_class(self._add_method_name, _add_child)
def _add_creator(self):
"""
Add a ``_new_{prop_name}()`` method to the element class that creates
a new, empty element of the correct type, having no attributes.
"""
creator = self._creator
creator.__doc__ = (
'Return a "loose", newly created ``<%s>`` element having no attri'
'butes, text, or children.' % self._nsptagname
)
self._add_to_class(self._new_method_name, creator)
def _add_getter(self):
"""
Add a read-only ``{prop_name}`` property to the element class for
this child element.
"""
property_ = property(self._getter, None, None)
# assign unconditionally to overwrite element name definition
setattr(self._element_cls, self._prop_name, property_)
def _add_inserter(self):
"""
Add an ``_insert_x()`` method to the element class for this child
element.
"""
def _insert_child(obj, child):
obj.insert_element_before(child, *self._successors)
return child
_insert_child.__doc__ = (
'Return the passed ``<%s>`` element after inserting it as a chil'
'd in the correct sequence.' % self._nsptagname
)
self._add_to_class(self._insert_method_name, _insert_child)
def _add_list_getter(self):
"""
Add a read-only ``{prop_name}_lst`` property to the element class to
retrieve a list of child elements matching this type.
"""
prop_name = '%s_lst' % self._prop_name
property_ = property(self._list_getter, None, None)
setattr(self._element_cls, prop_name, property_)
@lazyproperty
def _add_method_name(self):
return '_add_%s' % self._prop_name
def _add_public_adder(self):
"""
Add a public ``add_x()`` method to the parent element class.
"""
def add_child(obj):
private_add_method = getattr(obj, self._add_method_name)
child = private_add_method()
return child
add_child.__doc__ = (
'Add a new ``<%s>`` child element unconditionally, inserted in t'
'he correct sequence.' % self._nsptagname
)
self._add_to_class(self._public_add_method_name, add_child)
def _add_to_class(self, name, method):
"""
Add *method* to the target class as *name*, unless *name* is already
defined on the class.
"""
if hasattr(self._element_cls, name):
return
setattr(self._element_cls, name, method)
@property
def _creator(self):
"""
Return a function object that creates a new, empty element of the
right type, having no attributes.
"""
def new_child_element(obj):
return OxmlElement(self._nsptagname)
return new_child_element
@property
def _getter(self):
"""
Return a function object suitable for the "get" side of the property
descriptor. This default getter returns the child element with
matching tag name or |None| if not present.
"""
def get_child_element(obj):
return obj.find(qn(self._nsptagname))
get_child_element.__doc__ = (
'``<%s>`` child element or |None| if not present.'
% self._nsptagname
)
return get_child_element
@lazyproperty
def _insert_method_name(self):
return '_insert_%s' % self._prop_name
@property
def _list_getter(self):
"""
Return a function object suitable for the "get" side of a list
property descriptor.
"""
def get_child_element_list(obj):
return obj.findall(qn(self._nsptagname))
get_child_element_list.__doc__ = (
'A list containing each of the ``<%s>`` child elements, in the o'
'rder they appear.' % self._nsptagname
)
return get_child_element_list
@lazyproperty
def _public_add_method_name(self):
"""
add_childElement() is public API for a repeating element, allowing
new elements to be added to the sequence. May be overridden to
provide a friendlier API to clients having domain appropriate
parameter names for required attributes.
"""
return 'add_%s' % self._prop_name
@lazyproperty
def _remove_method_name(self):
return '_remove_%s' % self._prop_name
@lazyproperty
def _new_method_name(self):
return '_new_%s' % self._prop_name
class Choice(_BaseChildElement):
"""
Defines a child element belonging to a group, only one of which may
appear as a child.
"""
@property
def nsptagname(self):
return self._nsptagname
def populate_class_members(
self, element_cls, group_prop_name, successors):
"""
Add the appropriate methods to *element_cls*.
"""
self._element_cls = element_cls
self._group_prop_name = group_prop_name
self._successors = successors
self._add_getter()
self._add_creator()
self._add_inserter()
self._add_adder()
self._add_get_or_change_to_method()
def _add_get_or_change_to_method(self):
"""
Add a ``get_or_change_to_x()`` method to the element class for this
child element.
"""
def get_or_change_to_child(obj):
child = getattr(obj, self._prop_name)
if child is not None:
return child
remove_group_method = getattr(
obj, self._remove_group_method_name
)
remove_group_method()
add_method = getattr(obj, self._add_method_name)
child = add_method()
return child
get_or_change_to_child.__doc__ = (
'Return the ``<%s>`` child, replacing any other group element if'
' found.'
) % self._nsptagname
self._add_to_class(
self._get_or_change_to_method_name, get_or_change_to_child
)
@property
def _prop_name(self):
"""
Calculate property name from tag name, e.g. a:schemeClr -> schemeClr.
"""
if ':' in self._nsptagname:
start = self._nsptagname.index(':')+1
else:
start = 0
return self._nsptagname[start:]
@lazyproperty
def _get_or_change_to_method_name(self):
return 'get_or_change_to_%s' % self._prop_name
@lazyproperty
def _remove_group_method_name(self):
return '_remove_%s' % self._group_prop_name
class OneAndOnlyOne(_BaseChildElement):
"""
Defines a required child element for MetaOxmlElement.
"""
def __init__(self, nsptagname):
super(OneAndOnlyOne, self).__init__(nsptagname, None)
def populate_class_members(self, element_cls, prop_name):
"""
Add the appropriate methods to *element_cls*.
"""
super(OneAndOnlyOne, self).populate_class_members(
element_cls, prop_name
)
self._add_getter()
@property
def _getter(self):
"""
Return a function object suitable for the "get" side of the property
descriptor.
"""
def get_child_element(obj):
child = obj.find(qn(self._nsptagname))
if child is None:
raise InvalidXmlError(
"required ``<%s>`` child element not present" %
self._nsptagname
)
return child
get_child_element.__doc__ = (
'Required ``<%s>`` child element.'
% self._nsptagname
)
return get_child_element
class OneOrMore(_BaseChildElement):
"""
Defines a repeating child element for MetaOxmlElement that must appear at
least once.
"""
def populate_class_members(self, element_cls, prop_name):
"""
Add the appropriate methods to *element_cls*.
"""
super(OneOrMore, self).populate_class_members(
element_cls, prop_name
)
self._add_list_getter()
self._add_creator()
self._add_inserter()
self._add_adder()
self._add_public_adder()
delattr(element_cls, prop_name)
class ZeroOrMore(_BaseChildElement):
"""
Defines an optional repeating child element for MetaOxmlElement.
"""
def populate_class_members(self, element_cls, prop_name):
"""
Add the appropriate methods to *element_cls*.
"""
super(ZeroOrMore, self).populate_class_members(
element_cls, prop_name
)
self._add_list_getter()
self._add_creator()
self._add_inserter()
self._add_adder()
self._add_public_adder()
delattr(element_cls, prop_name)
class ZeroOrOne(_BaseChildElement):
"""
Defines an optional child element for MetaOxmlElement.
"""
def populate_class_members(self, element_cls, prop_name):
"""
Add the appropriate methods to *element_cls*.
"""
super(ZeroOrOne, self).populate_class_members(element_cls, prop_name)
self._add_getter()
self._add_creator()
self._add_inserter()
self._add_adder()
self._add_get_or_adder()
self._add_remover()
def _add_get_or_adder(self):
"""
Add a ``get_or_add_x()`` method to the element class for this
child element.
"""
def get_or_add_child(obj):
child = getattr(obj, self._prop_name)
if child is None:
add_method = getattr(obj, self._add_method_name)
child = add_method()
return child
get_or_add_child.__doc__ = (
'Return the ``<%s>`` child element, newly added if not present.'
) % self._nsptagname
self._add_to_class(self._get_or_add_method_name, get_or_add_child)
def _add_remover(self):
"""
Add a ``_remove_x()`` method to the element class for this child
element.
"""
def _remove_child(obj):
obj.remove_all(self._nsptagname)
_remove_child.__doc__ = (
'Remove all ``<%s>`` child elements.'
) % self._nsptagname
self._add_to_class(self._remove_method_name, _remove_child)
@lazyproperty
def _get_or_add_method_name(self):
return 'get_or_add_%s' % self._prop_name
class ZeroOrOneChoice(_BaseChildElement):
"""
Correspondes to an ``EG_*`` element group where at most one of its
members may appear as a child.
"""
def __init__(self, choices, successors=()):
self._choices = choices
self._successors = successors
def populate_class_members(self, element_cls, prop_name):
"""
Add the appropriate methods to *element_cls*.
"""
super(ZeroOrOneChoice, self).populate_class_members(
element_cls, prop_name
)
self._add_choice_getter()
for choice in self._choices:
choice.populate_class_members(
element_cls, self._prop_name, self._successors
)
self._add_group_remover()
def _add_choice_getter(self):
"""
Add a read-only ``{prop_name}`` property to the element class that
returns the present member of this group, or |None| if none are
present.
"""
property_ = property(self._choice_getter, None, None)
# assign unconditionally to overwrite element name definition
setattr(self._element_cls, self._prop_name, property_)
def _add_group_remover(self):
"""
Add a ``_remove_eg_x()`` method to the element class for this choice
group.
"""
def _remove_choice_group(obj):
for tagname in self._member_nsptagnames:
obj.remove_all(tagname)
_remove_choice_group.__doc__ = (
'Remove the current choice group child element if present.'
)
self._add_to_class(
self._remove_choice_group_method_name, _remove_choice_group
)
@property
def _choice_getter(self):
"""
Return a function object suitable for the "get" side of the property
descriptor.
"""
def get_group_member_element(obj):
return obj.first_child_found_in(*self._member_nsptagnames)
get_group_member_element.__doc__ = (
'Return the child element belonging to this element group, or '
'|None| if no member child is present.'
)
return get_group_member_element
@lazyproperty
def _member_nsptagnames(self):
"""
Sequence of namespace-prefixed tagnames, one for each of the member
elements of this choice group.
"""
return [choice.nsptagname for choice in self._choices]
@lazyproperty
def _remove_choice_group_method_name(self):
return '_remove_%s' % self._prop_name
class _OxmlElementBase(etree.ElementBase):
"""
Effective base class for all custom element classes, to add standardized
behavior to all classes in one place. Actual inheritance is from
BaseOxmlElement below, needed to manage Python 2-3 metaclass declaration
compatibility.
"""
__metaclass__ = MetaOxmlElement
def __repr__(self):
return "<%s '<%s>' at 0x%0x>" % (
self.__class__.__name__, self._nsptag, id(self)
)
def first_child_found_in(self, *tagnames):
"""
Return the first child found with tag in *tagnames*, or None if
not found.
"""
for tagname in tagnames:
child = self.find(qn(tagname))
if child is not None:
return child
return None
def insert_element_before(self, elm, *tagnames):
successor = self.first_child_found_in(*tagnames)
if successor is not None:
successor.addprevious(elm)
else:
self.append(elm)
return elm
def remove_all(self, *tagnames):
"""
Remove all child elements whose tagname (e.g. 'a:p') appears in
*tagnames*.
"""
for tagname in tagnames:
matching = self.findall(qn(tagname))
for child in matching:
self.remove(child)
@property
def xml(self):
"""
Return XML string for this element, suitable for testing purposes.
Pretty printed for readability and without an XML declaration at the
top.
"""
return serialize_for_reading(self)
def xpath(self, xpath_str):
"""
Override of ``lxml`` _Element.xpath() method to provide standard Open
XML namespace mapping (``nsmap``) in centralized location.
"""
return super(BaseOxmlElement, self).xpath(
xpath_str, namespaces=nsmap
)
@property
def _nsptag(self):
return NamespacePrefixedTag.from_clark_name(self.tag)
BaseOxmlElement = MetaOxmlElement(
'BaseOxmlElement', (etree.ElementBase,), dict(_OxmlElementBase.__dict__)
)