# pyright: reportImportCycles=false
"""Enabling declarative definition of lxml custom element classes."""
from __future__ import annotations
import re
from typing import (
TYPE_CHECKING,
Any,
Callable,
Dict,
List,
Sequence,
Tuple,
Type,
TypeVar,
)
from lxml import etree
from lxml.etree import ElementBase, _Element # pyright: ignore[reportPrivateUsage]
from docx.oxml.exceptions import InvalidXmlError
from docx.oxml.ns import NamespacePrefixedTag, nsmap, qn
from docx.shared import lazyproperty
if TYPE_CHECKING:
from docx.enum.base import BaseXmlEnum
from docx.oxml.simpletypes import BaseSimpleType
def serialize_for_reading(element: ElementBase):
"""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(str):
"""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(r"( *</?[\w:]+)(.*?)(/?>)([^<]*</[\w:]+>)?$")
def __eq__(self, other: object) -> bool:
if not isinstance(other, str):
return False
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: object) -> bool:
return not self.__eq__(other)
def _attr_seq(self, attrs: str) -> List[str]:
"""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: str, line_2: str):
"""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: str) -> Tuple[str, str, str, str]:
"""(front, attrs, close, text) 4-tuple result of parsing XML element `line`."""
match = cls._xml_elm_line_patt.match(line)
if match is None:
return "", "", "", ""
front, attrs, close, text = [match.group(n) for n in range(1, 5)]
return front, attrs, close, text
_T = TypeVar("_T")
class MetaOxmlElement(type):
"""Metaclass for BaseOxmlElement."""
def __init__(cls, clsname: str, bases: Tuple[type, ...], namespace: Dict[str, Any]):
dispatchable = (
OneAndOnlyOne,
OneOrMore,
OptionalAttribute,
RequiredAttribute,
ZeroOrMore,
ZeroOrOne,
ZeroOrOneChoice,
)
for key, value in namespace.items():
if isinstance(value, dispatchable):
value.populate_class_members(cls, key)
class BaseAttribute:
"""Base class for OptionalAttribute and RequiredAttribute.
Provides common methods.
"""
def __init__(self, attr_name: str, simple_type: Type[BaseXmlEnum] | Type[BaseSimpleType]):
super(BaseAttribute, self).__init__()
self._attr_name = attr_name
self._simple_type = simple_type
def populate_class_members(self, element_cls: MetaOxmlElement, prop_name: str) -> None:
"""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.
The property 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
@property
def _getter(self) -> Callable[[BaseOxmlElement], Any | None]: ...
@property
def _setter(
self,
) -> Callable[[BaseOxmlElement, Any | None], None]: ...
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, but still returns the default value when
one is specified.
"""
def __init__(
self,
attr_name: str,
simple_type: Type[BaseXmlEnum] | Type[BaseSimpleType],
default: BaseXmlEnum | BaseSimpleType | str | bool | None = None,
):
super(OptionalAttribute, self).__init__(attr_name, simple_type)
self._default = default
@property
def _docstring(self):
"""String to use as `__doc__` attribute of attribute property."""
return (
f"{self._simple_type.__name__} type-converted value of"
f" ``{self._attr_name}`` attribute, or |None| (or specified default"
f" value) if not present. Assigning the default value causes the"
f" attribute to be removed from the element."
)
@property
def _getter(
self,
) -> Callable[[BaseOxmlElement], Any | None]:
"""Function suitable for `__get__()` method on attribute property descriptor."""
def get_attr_value(
obj: BaseOxmlElement,
) -> Any | None:
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 _setter(self) -> Callable[[BaseOxmlElement, Any], None]:
"""Function suitable for `__set__()` method on attribute property descriptor."""
def set_attr_value(obj: BaseOxmlElement, value: Any | None):
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)
if str_value is None:
if self._clark_name in obj.attrib:
del obj.attrib[self._clark_name]
return
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 _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 _getter(self) -> Callable[[BaseOxmlElement], Any]:
"""function object suitable for "get" side of attr property descriptor."""
def get_attr_value(obj: BaseOxmlElement) -> Any | None:
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 _setter(self) -> Callable[[BaseOxmlElement, Any], None]:
"""function object suitable for "set" side of attribute property descriptor."""
def set_attr_value(obj: BaseOxmlElement, value: Any):
str_value = self._simple_type.to_xml(value)
if str_value is None:
raise ValueError(f"cannot assign {value} to this required attribute")
obj.set(self._clark_name, str_value)
return set_attr_value
class _BaseChildElement:
"""Base class for the child-element classes.
The child-element sub-classes correspond to varying cardinalities, such as ZeroOrOne
and ZeroOrMore.
"""
def __init__(self, nsptagname: str, successors: Tuple[str, ...] = ()):
super(_BaseChildElement, self).__init__()
self._nsptagname = nsptagname
self._successors = successors
def populate_class_members(self, element_cls: MetaOxmlElement, prop_name: str) -> None:
"""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: BaseOxmlElement, **attrs: Any):
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: BaseOxmlElement, child: BaseOxmlElement):
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: BaseOxmlElement):
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: str, method: Callable[..., Any]):
"""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) -> Callable[[BaseOxmlElement], BaseOxmlElement]:
"""Callable that creates an empty element of the right type, with no attrs."""
from docx.oxml.parser import OxmlElement
def new_child_element(obj: BaseOxmlElement):
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: BaseOxmlElement):
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: BaseOxmlElement):
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( # pyright: ignore[reportIncompatibleMethodOverride]
self,
element_cls: MetaOxmlElement,
group_prop_name: str,
successors: Tuple[str, ...],
) -> None:
"""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: BaseOxmlElement):
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):
"""Property name computed from tag name, e.g. a:schemeClr -> schemeClr."""
start = self._nsptagname.index(":") + 1 if ":" in self._nsptagname else 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: str):
super(OneAndOnlyOne, self).__init__(nsptagname, ())
def populate_class_members(self, element_cls: MetaOxmlElement, prop_name: str) -> None:
"""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: BaseOxmlElement):
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: MetaOxmlElement, prop_name: str) -> None:
"""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: MetaOxmlElement, prop_name: str) -> None:
"""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: MetaOxmlElement, prop_name: str) -> None:
"""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: BaseOxmlElement):
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: BaseOxmlElement):
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: Sequence[Choice], successors: Tuple[str, ...] = ()):
self._choices = choices
self._successors = successors
def populate_class_members(self, element_cls: MetaOxmlElement, prop_name: str) -> None:
"""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: BaseOxmlElement):
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: BaseOxmlElement):
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
# -- lxml typing isn't quite right here, just ignore this error on _Element --
class BaseOxmlElement(etree.ElementBase, metaclass=MetaOxmlElement):
"""Effective base class for all custom element classes.
Adds standardized behavior to all classes in one place.
"""
def __repr__(self):
return "<%s '<%s>' at 0x%0x>" % (
self.__class__.__name__,
self._nsptag,
id(self),
)
def first_child_found_in(self, *tagnames: str) -> _Element | None:
"""First child 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: ElementBase, *tagnames: str):
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: str) -> None:
"""Remove child elements with tagname (e.g. "a:p") in `tagnames`."""
for tagname in tagnames:
matching = self.findall(qn(tagname))
for child in matching:
self.remove(child)
@property
def xml(self) -> str:
"""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: str) -> Any: # pyright: ignore[reportIncompatibleMethodOverride]
"""Override of `lxml` _Element.xpath() method.
Provides standard Open XML namespace mapping (`nsmap`) in centralized location.
"""
return super().xpath(xpath_str, namespaces=nsmap)
@property
def _nsptag(self) -> str:
return NamespacePrefixedTag.from_clark_name(self.tag)
