Source code for aioxmpp.xso.model

"""
:mod:`aioxmpp.xso.model` --- Declarative-style XSO definition
#############################################################

See :mod:`aioxmpp.xso` for documentation.
"""
import abc
import collections
import copy
import logging
import sys
import xml.sax.handler

import lxml.sax

import orderedset  # get it from PyPI

import multidict  # get it from PyPI

from enum import Enum

from aioxmpp.utils import etree, namespaces

from . import query as xso_query
from . import types as xso_types
from . import tag_to_str, normalize_tag
from .. import structs


logger = logging.getLogger(__name__)


class UnknownChildPolicy(Enum):
    """
    Describe the event which shall take place whenever a child element is
    encountered for which no descriptor can be found to parse it.

    .. attribute:: FAIL

       Raise a :class:`ValueError`

    .. attribute:: DROP

       Drop and ignore the element and all of its children

    """

    FAIL = 0
    DROP = 1


class UnknownAttrPolicy(Enum):
    """
    Describe the event which shall take place whenever a XML attribute is
    encountered for which no descriptor can be found to parse it.

    .. attribute:: FAIL

       Raise a :class:`ValueError`

    .. attribute:: DROP

       Drop and ignore the attribute

    """
    FAIL = 0
    DROP = 1


class UnknownTextPolicy(Enum):
    """
    Describe the event which shall take place whenever XML character data is
    encountered on an object which does not support it.

    .. attribute:: FAIL

       Raise a :class:`ValueError`

    .. attribute:: DROP

       Drop and ignore the text

    """
    FAIL = 0
    DROP = 1


class ValidateMode(Enum):
    """
    Control which ways to set a value in a descriptor are passed through a
    validator.

    .. attribute:: FROM_RECV

       Values which are obtained from XML source are validated.

    .. attribute:: FROM_CODE

       Values which are set through attribute access are validated.

    .. attribute:: ALWAYS

       All values, whether set by attribute or obtained from XML source, are
       validated.

    """

    FROM_RECV = 1
    FROM_CODE = 2
    ALWAYS = 3

    @property
    def from_recv(self):
        return self.value & 1

    @property
    def from_code(self):
        return self.value & 2


class UnknownTopLevelTag(ValueError):
    """
    Subclass of :class:`ValueError`. `ev_args` must be the arguments of the
    ``"start"`` event and are stored as the :attr:`ev_args` attribute for
    inspection.

    .. attribute:: ev_args

       The `ev_args` passed to the constructor.

    """

    def __init__(self, msg, ev_args):
        super().__init__(msg + ": {}".format((ev_args[0], ev_args[1])))
        self.ev_args = ev_args


[docs]class XSOList(list): """ A :class:`list` subclass; it provides the complete :class:`list` interface with the addition of the following methods: .. automethod:: filter .. automethod:: filtered In the future, methods to add indices to :class:`XSOList` instances may be added; right now, there is no need for the huge complexity which would arise from keeping the indices up-to-date with changes in the elements attributes. """ def _filter_type(self, chained_results, type_): return (obj for obj in chained_results if isinstance(obj, type_)) def _filter_lang(self, chained_results, lang): # first, filter on availability of the "lang" attribute result = [item for item in chained_results if hasattr(item, "lang") and item.lang is not None] # get a sorted list of all languages in the current result set languages = sorted( {item.lang for item in result} ) if not languages: # no languages -> no results result = iter([]) else: # lookup a matching language if isinstance(lang, structs.LanguageRange): lang = [lang] else: lang = list(lang) match = structs.lookup_language(languages, lang) # no language? fallback is using the first one if match is None: match = languages[0] result = (item for item in result if item.lang == match) return result def _filter_attrs(self, chained_results, attrs): result = chained_results for key, value in attrs.items(): result = (item for item in result if hasattr(item, key) and getattr(item, key) == value) return result
[docs] def filter(self, *, type_=None, lang=None, attrs={}): """ Return an iterable which produces a sequence of the elements inside this :class:`XSOList`, filtered by the criteria given as arguments. The fucntion starts with a working sequence consisting of the whole list. If `type_` is not :data:`None`, elements which are not an instance of the given type are excluded from the working sequence. If `lang` is not :data:`None`, it must be either a :class:`~.structs.LanguageRange` or an iterable of language ranges. The set of languages present among the working sequence is determined and used for a call to :class:`~.structs.lookup_language`. If the lookup returns a language, all elements whose :attr:`lang` is different from that value are excluded from the working sequence. .. note:: If an iterable of language ranges is given, it is evaluated into a list. This may be of concern if a huge iterable is about to be used for language ranges, but it is an requirement of the :class:`~.structs.lookup_language` function which is used under the hood. .. note:: Filtering by language assumes that the elements have a :class:`~aioxmpp.xso.LangAttr` descriptor named ``lang``. If `attrs` is not empty, the filter iterates over each `key`-`value` pair. For each iteration, all elements which do not have an attribute of the name in `key` or where that attribute has a value not equal to `value` are excluded from the working sequence. In general, the iterable returned from :meth:`filter` can only be used once. It is dynamic in the sense that changes to elements which are in the list *behind* the last element returned from the iterator will still be picked up when the iterator is resumed. """ result = self if type_ is not None: result = self._filter_type(result, type_) if lang is not None: result = self._filter_lang(result, lang) if attrs: result = self._filter_attrs(result, attrs) return result
[docs] def filtered(self, *, type_=None, lang=None, attrs={}): """ This method is a convencience wrapper around :meth:`filter` which evaluates the result into a list and returns that list. """ return list(self.filter(type_=type_, lang=lang, attrs=attrs))
class PropBaseMeta(type): def __instancecheck__(self, instance): if (isinstance(instance, xso_query.BoundDescriptor) and super().__instancecheck__(instance.xq_descriptor)): return True return super().__instancecheck__(instance) class _PropBase(metaclass=PropBaseMeta): class NO_DEFAULT: def __repr__(self): return "no default" def __bool__(self): raise TypeError("cannot convert NO_DEFAULT to bool") NO_DEFAULT = NO_DEFAULT() def __init__(self, default=NO_DEFAULT, *, validator=None, validate=ValidateMode.FROM_RECV): super().__init__() self.default = default self.validate = validate self.validator = validator def _set(self, instance, value): instance._xso_contents[self] = value def __set__(self, instance, value): if (self.validate.from_code and self.validator and not self.validator.validate(value)): raise ValueError("invalid value") self._set(instance, value) def _set_from_code(self, instance, value): self.__set__(instance, value) def _set_from_recv(self, instance, value): if (self.validate.from_recv and self.validator and not self.validator.validate(value)): raise ValueError("invalid value") self._set(instance, value) def __get__(self, instance, type_): if instance is None: return xso_query.BoundDescriptor( type_, self, xso_query.GetDescriptor, ) try: return instance._xso_contents[self] except KeyError: if self.default is self.NO_DEFAULT: raise AttributeError( "attribute is unset ({} on instance of {})".format( self, type_) ) from None return self.default def validate_contents(self, instance): try: self.__get__(instance, type(instance)) except AttributeError as exc: raise ValueError(str(exc)) from None def to_node(self, instance, parent): handler = lxml.sax.ElementTreeContentHandler( makeelement=parent.makeelement) handler.startDocument() handler.startElementNS((None, "_"), None, {}) self.to_sax(instance, handler) parent.extend(handler.etree.getroot()) class _TypedPropBase(_PropBase): def __init__(self, *, type_=xso_types.String(), **kwargs): super().__init__(**kwargs) self.type_ = type_ def __set__(self, instance, value): if value is not None: value = self.type_.coerce(value) super().__set__(instance, value) class Text(_TypedPropBase): """ When assigned to a class’ attribute, it collects all character data of the XML element. Note that this destroys the relative ordering of child elements and character data pieces. This is known and a WONTFIX, as it is not required in XMPP to keep that relative order: Elements either have character data *or* other elements as children. The `type_`, `validator`, `validate` and `default` arguments behave like in :class:`Attr`. .. automethod:: from_value .. automethod:: to_sax """ def from_value(self, instance, value): """ Convert the given value using the set `type_` and store it into `instance`’ attribute. """ self._set_from_recv(instance, self.type_.parse(value)) def to_sax(self, instance, dest): """ Assign the formatted value stored at `instance`’ attribute to the text of `el`. If the `value` is :data:`None`, no text is generated. """ value = self.__get__(instance, type(instance)) if value is None: return dest.characters(self.type_.format(value)) class _ChildPropBase(_PropBase): """ This is a base class for descriptors related to child :class:`XSO` instances. It provides a few implementation parts shared between :class:`Child`, :class:`ChildList` and :class:`ChildMap`. """ def __init__(self, classes, default=None): super().__init__(default) self._classes = set() self._tag_map = {} for cls in classes: self._register(cls) def _process(self, instance, ev_args, ctx): cls = self._tag_map[ev_args[0], ev_args[1]] return (yield from cls.parse_events(ev_args, ctx)) def get_tag_map(self): """ Return a dictionary mapping the tags of the supported classes to the classes themselves. Can be used to obtain a set of supported tags. """ return self._tag_map def _register(self, cls): if cls.TAG in self._tag_map: raise ValueError("ambiguous children: {} and {} share the same " "TAG".format( self._tag_map[cls.TAG], cls)) self._tag_map[cls.TAG] = cls self._classes.add(cls) class Child(_ChildPropBase): """ When assigned to a class’ attribute, it collects any child which matches any :attr:`XSO.TAG` of the given `classes`. The tags among the `classes` must be unique, otherwise :class:`ValueError` is raised on construction. Instead of the `default` argument like supplied by :class:`Attr`, :class:`Child` only supports `required`: if `required` is a false value (the default), a missing child is tolerated and :data:`None` is valid value for the described attribute. Otherwise, a missing matching child is an error and the attribute cannot be set to :data:`None`. .. automethod:: get_tag_map .. automethod:: from_events .. automethod:: to_sax """ def __init__(self, classes, required=False): super().__init__( classes, default=_PropBase.NO_DEFAULT if required else None ) @property def required(self): return self.default is _PropBase.NO_DEFAULT def __set__(self, instance, value): if value is None and self.required: raise ValueError("cannot set required member to None") super().__set__(instance, value) def __delete__(self, instance): if self.required: raise AttributeError("cannot delete required member") try: del instance._xso_contents[self] except KeyError: pass def from_events(self, instance, ev_args, ctx): """ Detect the object to instanciate from the arguments `ev_args` of the ``"start"`` event. The new object is stored at the corresponding descriptor attribute on `instance`. This method is suspendable. """ obj = yield from self._process(instance, ev_args, ctx) self.__set__(instance, obj) return obj def validate_contents(self, instance): try: obj = self.__get__(instance, type(instance)) except AttributeError: raise ValueError("missing required member") if obj is not None: obj.validate() def to_sax(self, instance, dest): """ Take the object associated with this descriptor on `instance` and serialize it as child into the given :class:`lxml.etree.Element` `parent`. If the object is :data:`None`, no content is generated. """ obj = self.__get__(instance, type(instance)) if obj is None: return obj.unparse_to_sax(dest) class ChildList(_ChildPropBase): """ The :class:`ChildList` works like :class:`Child`, with two key differences: * multiple children which are matched by this descriptor get collected into an :class:`~aioxmpp.xso.model.XSOList`. * the default is fixed at an empty list. * `required` is not supported .. automethod:: from_events .. automethod:: to_sax """ def __init__(self, classes): super().__init__(classes) def __get__(self, instance, type_): if instance is None: return xso_query.BoundDescriptor( type_, self, xso_query.GetSequenceDescriptor, ) return instance._xso_contents.setdefault(self, XSOList()) def _set(self, instance, value): if not isinstance(value, list): raise TypeError("expected list, but found {}".format(type(value))) return super()._set(instance, value) def from_events(self, instance, ev_args, ctx): """ Like :meth:`.Child.from_events`, but instead of replacing the attribute value, the new object is appended to the list. """ obj = yield from self._process(instance, ev_args, ctx) self.__get__(instance, type(instance)).append(obj) return obj def validate_contents(self, instance): for child in self.__get__(instance, type(instance)): child.validate() def to_sax(self, instance, dest): """ Like :meth:`.Child.to_node`, but instead of serializing a single object, all objects in the list are serialized. """ for obj in self.__get__(instance, type(instance)): obj.unparse_to_sax(dest) class Collector(_PropBase): """ When assigned to a class’ attribute, it collects all children which are not known to any other descriptor into a list of XML subtrees. The default is fixed at an empty list. .. automethod:: from_events .. automethod:: to_sax """ def __init__(self): super().__init__(default=[]) def __get__(self, instance, type_): if instance is None: return xso_query.BoundDescriptor( type_, self, xso_query.GetSequenceDescriptor, ) return instance._xso_contents.setdefault(self, []) def _set(self, instance, value): if not isinstance(value, list): raise TypeError("expected list, but found {}".format(type(value))) return super()._set(instance, value) def from_events(self, instance, ev_args, ctx): """ Collect the events and convert them to a single XML subtree, which then gets appended to the list at `instance`. `ev_args` must be the arguments of the ``"start"`` event of the new child. This method is suspendable. """ # goal: collect all elements starting with the element for which we got # the start-ev_args in a lxml.etree.Element. def make_from_args(ev_args, parent): if parent is not None: el = etree.SubElement(parent, tag_to_str((ev_args[0], ev_args[1]))) else: el = etree.Element(tag_to_str((ev_args[0], ev_args[1]))) for key, value in ev_args[2].items(): el.set(tag_to_str(key), value) return el root_el = make_from_args(ev_args, None) # create an element stack stack = [root_el] while stack: # we get send all sax-ish events until we return. we return when # the stack is empty, i.e. when our top element ended. ev_type, *ev_args = yield if ev_type == "start": # new element started, create and push to stack stack.append(make_from_args(ev_args, stack[-1])) elif ev_type == "text": # text for current element curr = stack[-1] if curr.text is not None: curr.text += ev_args[0] else: curr.text = ev_args[0] elif ev_type == "end": # element ended, remove from stack (it is already appended to # the current element) stack.pop() else: # not in coverage -- this is more like an assertion raise ValueError(ev_type) self.__get__(instance, type(instance)).append(root_el) def to_sax(self, instance, dest): for node in self.__get__(instance, type(instance)): lxml.sax.saxify(node, dest) class Attr(Text): """ When assigned to a class’ attribute, it binds that attribute to the XML attribute with the given `tag`. `tag` must be a valid input to :func:`normalize_tag`. The following arguments occur at several of the descriptor classes, and are all available at :class:`Attr`. :param type_: An object which fulfills the type interface proposed by :class:`~.xso.AbstractType`. Usually, this is defaulted to a :class:`~aioxmpp.xso.String` instance. :param validator: An object which has a :meth:`validate` method. That method receives a value which was either assigned to the property (depending on the `validate` argument) or parsed from XML (after it passed through `type_`). :param validate: A value from the :class:`ValidateMode` enum, which defines which values have to pass through the validator. At some points it makes sense to only validate outgoing values, but be liberal with incoming values. This defaults to :attr:`ValidateMode.FROM_RECV`. :param default: The value which the attribute has if no value has been assigned. This must be given to allow the attribute to be missing. It defaults to a special value. If the attribute has not been assigned to and `default` has not been set, accessing the attribute for reading raises :class:`AttributeError`. An attribute with `default` value is not emitted in the output. :param missing: A callable which takes a :class:`Context` instance. It is called whenever the attribute is missing (independent from the fact whether it is required or not). The callable shall return a not-:data:`None` value for the attribute to use. If the value is :data:`None`, the usual handling of missing attributes takes place. .. seealso:: :class:`LangAttr`, which is a subclass of :class:`Attr` specialized for describing ``xml:lang`` attributes. .. note:: The `default` argument does not need to comply with either `type_` or `validator`. This can be used to convey meaning with the absence of the attribute. Note that assigning the default value is not possible if it does not comply with `type_` or `validator` and the ``del`` operator must be used instead. .. automethod:: from_value .. automethod:: handle_missing .. automethod:: to_dict """ def __init__(self, tag, *, type_=xso_types.String(), missing=None, **kwargs): super().__init__(type_=type_, **kwargs) self.tag = normalize_tag(tag) self.missing = missing def __set__(self, instance, value): super().__set__(instance, value) def __delete__(self, instance): try: del instance._xso_contents[self] except KeyError: pass def handle_missing(self, instance, ctx): """ Handle a missing attribute on `instance`. This is called whenever no value for the attribute is found during parsing. The call to :meth:`missing` is independent of the value of `required`. If the `missing` callback is not :data:`None`, it is called with the `instance` and the `ctx` as arguments. If the returned value is not :data:`None`, it is used as the value of the attribute (validation takes place as if the value had been set from the code, not as if the value had been received from XML) and the handler returns. If the `missing` callback is :data:`None` or returns :data:`None`, the handling continues as normal: if `required` is true, a :class:`ValueError` is raised. """ if self.missing is not None: value = self.missing(instance, ctx) if value is not None: self._set_from_code(instance, value) return if self.default is _PropBase.NO_DEFAULT: raise ValueError("missing attribute {} on {}".format( tag_to_str(self.tag), tag_to_str(instance.TAG), )) # no need to set explicitly, it will be handled by _PropBase.__get__ def validate_contents(self, instance): try: self.__get__(instance, type(instance)) except AttributeError: raise ValueError("non-None value required for {}".format( tag_to_str(self.tag) )) from None def to_dict(self, instance, d): """ Override the implementation from :class:`Text` by storing the formatted value in the XML attribute instead of the character data. If the value is :data:`None`, no element is generated. """ value = self.__get__(instance, type(instance)) if value == self.default: return d[self.tag] = self.type_.format(value) class LangAttr(Attr): """ The :class:`LangAttr` is identical to :class:`Attr`, except that the `type_`, `tag` and `missing` arguments are already bound. The `tag` is set to the ``(namespaces.xml, "lang")`` value to match ``xml:lang`` attributes. `type_` is a :class:`xso.LanguageTag` instance and `missing` is set to :func:`lang_attr`. Note that :class:`LangAttr` overrides `default` to be :data:`None` by default. """ def __init__(self, default=None, **kwargs): super().__init__( (namespaces.xml, "lang"), default=default, type_=xso_types.LanguageTag(), missing=lang_attr ) class ChildText(_TypedPropBase): """ When assigned to a class’ attribute, it binds that attribute to the XML character data of a child element with the given `tag`. `tag` must be a valid input to :func:`normalize_tag`. The `type_`, `validate`, `validator` and `default` arguments behave like in :class:`Attr`. `child_policy` is applied when :meth:`from_events` encounters an element in the child element of which it is supposed to extract text. Likewise, `attr_policy` is applied if an attribute is encountered on the element. `declare_prefix` works as for :class:`ChildTag`. .. automethod:: get_tag_map .. automethod:: from_events .. automethod:: to_sax """ def __init__(self, tag, *, child_policy=UnknownChildPolicy.FAIL, attr_policy=UnknownAttrPolicy.FAIL, declare_prefix=False, **kwargs): super().__init__(**kwargs) self.tag = normalize_tag(tag) self.child_policy = child_policy self.attr_policy = attr_policy self.declare_prefix = declare_prefix def get_tag_map(self): """ Return an iterable yielding :attr:`tag`. This is for compatiblity with the :class:`Child` interface. """ return {self.tag} def from_events(self, instance, ev_args, ctx): """ Starting with the element to which the start event information in `ev_args` belongs, parse text data. If any children are encountered, :attr:`child_policy` is enforced (see :class:`UnknownChildPolicy`). Likewise, if the start event contains attributes, :attr:`attr_policy` is enforced (c.f. :class:`UnknownAttrPolicy`). The extracted text is passed through :attr:`type_` and :attr:`validator` and if it passes, stored in the attribute on the `instance` with which the property is associated. This method is suspendable. """ # goal: take all text inside the child element and collect it as # attribute value attrs = ev_args[2] if attrs and self.attr_policy == UnknownAttrPolicy.FAIL: raise ValueError("unexpected attribute (at text only node)") parts = [] while True: ev_type, *ev_args = yield if ev_type == "text": # collect ALL TEH TEXT! parts.append(ev_args[0]) elif ev_type == "start": # ok, a child inside the child was found, we look at our policy # to see what to do yield from enforce_unknown_child_policy( self.child_policy, ev_args) elif ev_type == "end": # end of our element, return break self._set_from_recv(instance, self.type_.parse("".join(parts))) def to_sax(self, instance, dest): """ Create a child node at `parent` with the tag :attr:`tag`. Set the text contents to the value of the attribute which this descriptor represents at `instance`. If the value is :data:`None`, no element is generated. """ value = self.__get__(instance, type(instance)) if value == self.default: return if self.declare_prefix is not False and self.tag[0]: dest.startPrefixMapping(self.declare_prefix, self.tag[0]) dest.startElementNS(self.tag, None, {}) try: dest.characters(self.type_.format(value)) finally: dest.endElementNS(self.tag, None) if self.declare_prefix is not False and self.tag[0]: dest.endPrefixMapping(self.declare_prefix) class ChildMap(_ChildPropBase): """ The :class:`ChildMap` class works like :class:`ChildList`, but instead of storing the child objects in a list, they are stored in a map which contains an :class:`~aioxmpp.xso.model.XSOList` of objects for each tag. `key` may be callable. If it is given, it is used while parsing to determine the dictionary key under which a newly parsed XSO will be put. For that, the `key` callable is called with the newly parsed XSO as the only argument and is expected to return the key. .. automethod:: from_events .. automethod:: to_sax The following utility function is useful when filling data into descriptors using this class: .. automethod:: fill_into_dict """ def __init__(self, classes, *, key=None): super().__init__(classes) self.key = key or (lambda obj: obj.TAG) def __get__(self, instance, type_): if instance is None: return xso_query.BoundDescriptor( type_, self, xso_query.GetMappingDescriptor, ) return instance._xso_contents.setdefault( self, collections.defaultdict(XSOList) ) def __set__(self, instance, value): raise AttributeError("ChildMap attribute cannot be assigned to") def _set(self, instance, value): if not isinstance(value, dict): raise TypeError("expected dict, but found {}".format(type(value))) return super()._set(instance, value) def fill_into_dict(self, items, dest): """ Take an iterable of `items` and group it into the given `dest` dict, using the :attr:`key` function. The `dest` dict must either already contain the keys which are generated by the :attr:`key` function for the items in `items`, or must default them suitably. The values of the affected keys must be sequences or objects with an :meth:`append` method which does what you want it to do. """ for item in items: dest[self.key(item)].append(item) def from_events(self, instance, ev_args, ctx): """ Like :meth:`.ChildList.from_events`, but the object is appended to the list associated with its tag in the dict. """ tag = ev_args[0], ev_args[1] cls = self._tag_map[tag] obj = yield from cls.parse_events(ev_args, ctx) mapping = self.__get__(instance, type(instance)) mapping[self.key(obj)].append(obj) def validate_contents(self, instance): mapping = self.__get__(instance, type(instance)) for objects in mapping.values(): for obj in objects: obj.validate() def to_sax(self, instance, dest): """ Serialize all objects in the dict associated with the descriptor at `instance` to the given `parent`. The order of elements within a tag is preserved; the order of the tags relative to each other is undefined. """ for items in self.__get__(instance, type(instance)).values(): for obj in items: obj.unparse_to_sax(dest) class ChildLangMap(ChildMap): """ The :class:`ChildLangMap` class is a specialized version of the :class:`ChildMap`, which uses a `key` function to group the children by their XML language tag. It is expected that the language tag is available as ``lang`` attribute on the objects stored in this map. """ @staticmethod def _lang_key(obj): return obj.lang def __init__(self, classes, **kwargs): super().__init__(classes, key=self._lang_key, **kwargs) class ChildTag(_PropBase): """ When assigned to a class’ attribute, this descriptor represents the presence or absence of a single child with a tag from a given set of valid tags. `tags` must be an iterable of valid arguments to :func:`normalize_tag`. If :func:`normalize_tag` returns a false value (such as :data:`None`) as `namespace_uri`, it is replaced with `default_ns` (defaulting to :data:`None`, which makes this sentence a no-op). This allows a benefit to readability if you have many tags which share the same namespace. `text_policy`, `child_policy` and `attr_policy` describe the behaviour if the child element unexpectedly has text, children or attributes, respectively. The default for each is to fail with a :class:`ValueError`. If `allow_none` is :data:`True`, assignment of :data:`None` to the attribute to which this descriptor belongs is allowed and represents the absence of the child element. If `declare_prefix` is not :data:`False` (note that :data:`None` is a valid, non-:data:`False` value in this context!), the namespace is explicitly declared using the given prefix when serializing to SAX. .. automethod:: from_events .. automethod:: to_sax """ class ElementTreeTag(xso_types.AbstractType): """ Parse an element-tree-format tag to a tuple-format tag. This type operates on strings and should not be used in general. """ def parse(self, v): return normalize_tag(v) def format(self, v): return tag_to_str(v) def __init__(self, tags, *, default_ns=None, text_policy=UnknownTextPolicy.FAIL, child_policy=UnknownChildPolicy.FAIL, attr_policy=UnknownAttrPolicy.FAIL, allow_none=False, declare_prefix=False): tags = { (ns or default_ns, localname) for ns, localname in map(normalize_tag, tags) } if allow_none: tags.add(None) super().__init__( default=None if allow_none else _PropBase.NO_DEFAULT, validator=xso_types.RestrictToSet(tags), validate=ValidateMode.ALWAYS) self.type_ = self.ElementTreeTag() self.text_policy = text_policy self.attr_policy = attr_policy self.child_policy = child_policy self.declare_prefix = declare_prefix @property def allow_none(self): return self.default is not _PropBase.NO_DEFAULT def get_tag_map(self): return self.validator.values def from_events(self, instance, ev_args, ctx): attrs = ev_args[2] if attrs and self.attr_policy == UnknownAttrPolicy.FAIL: raise ValueError("unexpected attributes") tag = ev_args[0], ev_args[1] while True: ev_type, *ev_args = yield if ev_type == "text": if self.text_policy == UnknownTextPolicy.FAIL: raise ValueError("unexpected text") elif ev_type == "start": yield from enforce_unknown_child_policy( self.child_policy, ev_args) elif ev_type == "end": break self._set_from_recv(instance, tag) def to_sax(self, instance, dest): value = self.__get__(instance, type(instance)) if value is None: return if self.declare_prefix is not False and value[0]: dest.startPrefixMapping(self.declare_prefix, value[0]) dest.startElementNS(value, None, {}) dest.endElementNS(value, None) if self.declare_prefix is not False and value[0]: dest.endPrefixMapping(self.declare_prefix) class ChildValueList(_ChildPropBase): """ A list of values, generated by child tags. This descriptor requires a single argument, the :class:`.xso.AbstractType` which implements the packing/unpacking of the native python values to XSOs. The `type_` must return a :class:`.xso.XSO` subclass from :meth:`.xso.AbstractType.get_formatted_type`. The :meth:`~.xso.AbstractType.parse` method receives the XSO as parsed from the events and is expected to return a non-XSO object. The :meth:`~.xso.AbstractType.format` method is called to prepare the values in the list for serialisation. It must return instances of :meth:`~.xso.AbstractType.get_formatted_type`, holding the value passed to :meth:`~.xso.AbstractType.format`. The XSO is then serialised as child of the object this descriptor is applied to. The optional `container_type` argument must, if given, be a callable which returns a mutable container supporting either :meth:`add` or :meth:`append` of the values used with the `type_` and iteration. It will be used instead of :class:`list` to create the values for the descriptor. .. versionadded:: 0.5 """ def __init__(self, type_, *, container_type=list): super().__init__([type_.get_formatted_type()]) self.type_ = type_ self.container_type = container_type try: self._add = container_type.append except AttributeError: self._add = container_type.add def __get__(self, instance, type_): if instance is None: return xso_query.BoundDescriptor( type_, self, xso_query.GetSequenceDescriptor, expr_kwargs={"sequence_factory": self.container_type}, ) try: return instance._xso_contents[self] except KeyError: result = self.container_type() instance._xso_contents[self] = result return result def __set__(self, instance, value): raise AttributeError("child value list not writable") def from_events(self, instance, ev_args, ctx): obj = yield from self._process(instance, ev_args, ctx) value = self.type_.parse(obj) self._add(self.__get__(instance, type(instance)), value) def to_sax(self, instance, dest): for value in self.__get__(instance, type(instance)): self.type_.format(value).unparse_to_sax(dest) class ChildValueMap(_ChildPropBase): """ A mapping of keys to values, generated by child tags. This works very similar to :class:`ChildValueList`, but instead of a mutable sequence, the value of the descriptor is a mutable mapping. The `type_` must return key-value pairs from :meth:`.xso.AbstractType.parse` and must accept such key-value pairs in :meth:`.xso.AbstractType.format`. The optional `mapping_type` argument must, if given, be a callable which returns a :class:`collections.abc.MutableMapping` supporting the keys and values used by the `type_`. It will be used instead of :class:`dict` to create the values for the descriptor. A possible use-case is using :class:`.structs.LanguageMap` together with :class:`~.xso.TextChildMap`. .. seealso:: :class:`ChildTextMap` for a specialised version to deal with :class:`AbstractTextChild` subclasses. .. versionadded:: 0.5 """ def __init__(self, type_, *, mapping_type=dict): super().__init__([type_.get_formatted_type()]) self.type_ = type_ self.mapping_type = mapping_type def __get__(self, instance, type_): if instance is None: return xso_query.BoundDescriptor( type_, self, xso_query.GetMappingDescriptor, expr_kwargs={"mapping_factory": self.mapping_type} ) try: return instance._xso_contents[self] except KeyError: result = self.mapping_type() instance._xso_contents[self] = result return result def __set__(self, instance, value): raise AttributeError("child value map not writable") def to_sax(self, instance, dest): for item in self.__get__(instance, type(instance)).items(): self.type_.format(item).unparse_to_sax(dest) def from_events(self, instance, ev_args, ctx): obj = yield from self._process(instance, ev_args, ctx) key, value = self.type_.parse(obj) self.__get__(instance, type(instance))[key] = value class ChildValueMultiMap(_ChildPropBase): """ A mapping of keys to lists of values, representing child tags. This is very similar to :class:`ChildValueMultiMap`, but it uses a :class:`multidict.MultiDict` as storage. Interface-compatible classes can be substituted by passing them to `mapping_type`. Candidate for that are :class:`multidict.CIMultiDict`. The `type_` must return key-value pairs from :meth:`.xso.AbstractType.parse` and must accept such key-value pairs in :meth:`.xso.AbstractType.format`. Each key-value pair consists of the respective dictionary key and a value from the list of values belonging to that dictionary key. .. versionadded:: 0.6 """ def __init__(self, type_, *, mapping_type=multidict.MultiDict): super().__init__([type_.get_formatted_type()]) self.type_ = type_ self.mapping_type = mapping_type def __get__(self, instance, type_): if instance is None: return xso_query.BoundDescriptor( type_, self, xso_query.GetMappingDescriptor, expr_kwargs={"mapping_factory": self.mapping_type}, ) try: return instance._xso_contents[self] except KeyError: result = self.mapping_type() instance._xso_contents[self] = result return result def __set__(self, instance, value): raise AttributeError("child value multi map not writable") def to_sax(self, instance, dest): for key, values in self.__get__(instance, type(instance)).items(): for value in values: self.type_.format((key, value)).unparse_to_sax(dest) def from_events(self, instance, ev_args, ctx): obj = yield from self._process(instance, ev_args, ctx) key, value = self.type_.parse(obj) self.__get__(instance, type(instance)).add(key, value) class ChildTextMap(ChildValueMap): """ A specialised version of :class:`ChildValueMap` which uses :class:`TextChildMap` together with :class:`.structs.LanguageMap` to convert the :class:`AbstractTextChild` subclass `xso_type` to and from a language-text mapping. For an example, see :class:`.stanza.Message`. """ def __init__(self, xso_type): super().__init__( xso_types.TextChildMap(xso_type), mapping_type=structs.LanguageMap )
[docs]class XMLStreamClass(xso_query.Class, abc.ABCMeta): """ This metaclass is used to implement the fancy features of :class:`.XSO` classes and instances. Its documentation details on some of the restrictions and features of XML Stream Classes. .. note:: There should be no need to use this metaclass directly when implementing your own XSO classes. Instead, derive from :class:`~.xso.XSO`. The following restrictions apply when a class uses the :class:`XMLStreamClass` metaclass: 1. At no point in the inheritance tree there must exist more than one distinct :class:`~.xso.Text` descriptor. It is possible to inherit two identical text descriptors from several base classes though. 2. The above applies equivalently for :class:`~.xso.Collector` descriptors. 3. At no point in the inheritance tree there must exist more than one :class:`~.xso.Attr` descriptor which handles a given attribute tag. Like with :class:`~.xso.Text`, it is allowed that the same :class:`~.xso.Attr` descriptor is inherited through multiple paths from parent classes. 4. The above applies likewise for element tags and :class:`~.xso.Child` (or similar) descriptors. Objects of this metaclass (i.e. classes) have some useful attributes. The following attributes are gathered from the namespace of the class, by collecting the different XSO-related descriptors: .. attribute:: TEXT_PROPERTY The :class:`~.xso.Text` descriptor object associated with this class. This is :data:`None` if no attribute using that descriptor is declared on the class. .. attribute:: COLLECTOR_PROPERTY The :class:`~.xso.Collector` descriptor object associated with this class. This is :data:`None` if no attribute using that descriptor is declared on the class. .. attribute:: ATTR_MAP A dictionary mapping attribute tags to the :class:`~.xso.Attr` descriptor objects for these attributes. .. attribute:: CHILD_MAP A dictionary mapping element tags to the :class:`~.xso.Child` (or similar) descriptor objects which accept these child elements. .. attribute:: CHILD_PROPS A set of all :class:`~.xso.Child` (or :class:`~.xso.ChildList`) descriptor objects of this class. .. attribute:: DECLARE_NS A dictionary which defines the namespace mappings which shall be declared when serializing this element. It must map namespace prefixes (such as :data:`None` or ``"foo"``) to namespace URIs. For maximum compatibility with legacy XMPP implementations (I’m looking at you, ejabberd!), :attr:`DECLARE_NS` is set by this metaclass unless it is provided explicitly when declaring the class: * If no :attr:`TAG` is set, :attr:`DECLARE_NS` is also not set. The attribute does not exist on the class in that case, unless it is inherited from a base class. * If :attr:`TAG` is set and at least one base class has a :attr:`DECLARE_NS`, :attr:`DECLARE_NS` is not auto generated, so that inheritance can take place. * If :attr:`TAG` is set and has a namespace (and no base class has a :attr:`DECLARE_NS`), :attr:`DECLARE_NS` is set to ``{ None: namespace }``, where ``namespace`` is the namespace of the :attr:`TAG`. * If :attr:`TAG` is set and does not have a namespace, :attr:`DECLARE_NS` is set to the empty dict. This should not occur outside testing, and support for tags without namespace might be removed in future versions. .. warning:: It is discouraged to use namespace prefixes of the format ``"ns{:d}".format(n)``, for any given number `n`. These prefixes are reserved for ad-hoc namespace declarations, and attempting to use them may have unwanted side-effects. .. versionchanged:: 0.4 The automatic generation of the :attr:`DECLARE_NS` attribute was added in 0.4. .. attribute:: __slots__ The metaclass automatically sets this attribute to the empty tuple, unless a different value is set in the class or `protect` is passed as false to the metaclass. Thus, to disable the automatic setting of :attr:`__slots__`, inherit for example like this:: class MyXSO(xso.XSO, protect=False): pass The rationale for this is that attributes on XSO instances are magic. Having a typo in an attribute may fail non-obviously, if it causes an entirely different semantic to be invoked at the peer (for example the :attr:`.stanza.Message.type_` attribute). Setting :attr:`__slots__` to empty by default prevents assigning any attribute not bound to an descriptor.` .. seealso:: :ref:`slots` The official Python documentation describes the semantics of the :attr:`__slots__` attribute in more detail. :class:`~.xso.XSO` automatically sets a sensible :attr:`__slots__` (including ``__weakref__``, but not ``__dict__``). .. versionadded:: 0.6 .. note:: If you need to stay compatible with versions before 0.6 *and* have arbitrary attributes writable, the correct way of doing things is to explicitly set :attr:`__slots__` to ``("__dict__",)`` in your class. You cannot use `protect` because it is not known in pre-0.6 versions. .. note:: :class:`~.xso.XSO` defines defaults for more attributes which also must be present on objects which are used as XSOs. When inheriting from :class:`XMLStreamClass` objects, the properties are merged sensibly. Rebinding attributes of :class:`XMLStreamClass` instances (i.e. classes using this metaclass) is somewhat restricted. The following rules cannot be broken, attempting to do so will result in :class:`TypeError` being raised when setting the attribute: 1. Existing descriptors for XSO purposes (such as :class:`.xso.Attr`) cannot be removed (either by assigning a new value to the name they are bound to or deleting the name). 2. New descriptors can only be added if they do not violate the rules stated at the beginning of the :class:`XMLStreamClass` documentation. 3. New descriptors can only be added if no subclasses exist (see :meth:`.xso.XSO.register_child` for reasons why). """ def __new__(mcls, name, bases, namespace, protect=True): text_property = None child_map = {} child_props = orderedset.OrderedSet() attr_map = {} collector_property = None for base in reversed(bases): if not isinstance(base, XMLStreamClass): continue if base.TEXT_PROPERTY is not None: if (text_property is not None and base.TEXT_PROPERTY.xq_descriptor is not text_property): raise TypeError("multiple text properties in inheritance") text_property = base.TEXT_PROPERTY.xq_descriptor for key, prop in base.CHILD_MAP.items(): try: existing = child_map[key] except KeyError: child_map[key] = prop else: if existing is not prop: raise TypeError("ambiguous Child properties inherited") child_props |= base.CHILD_PROPS for key, prop in base.ATTR_MAP.items(): try: existing = attr_map[key] except KeyError: attr_map[key] = prop else: if existing is not prop: raise TypeError("ambiguous Attr properties inherited") if base.COLLECTOR_PROPERTY is not None: if (collector_property is not None and base.COLLECTOR_PROPERTY.xq_descriptor is not collector_property): raise TypeError("multiple collector properties in " "inheritance") collector_property = base.COLLECTOR_PROPERTY.xq_descriptor for attrname, obj in namespace.items(): if isinstance(obj, Attr): if obj.tag in attr_map: raise TypeError("ambiguous Attr properties") attr_map[obj.tag] = obj elif isinstance(obj, Text): if text_property is not None: raise TypeError("multiple Text properties on XSO class") text_property = obj elif isinstance(obj, (_ChildPropBase, ChildText, ChildTag)): for key in obj.get_tag_map(): if key in child_map: raise TypeError("ambiguous Child properties: {} and {}" " both use the same tag".format( child_map[key], obj)) child_map[key] = obj child_props.add(obj) elif isinstance(obj, Collector): if collector_property is not None: raise TypeError("multiple Collector properties on XSO " "class") collector_property = obj namespace["TEXT_PROPERTY"] = text_property namespace["CHILD_MAP"] = child_map namespace["CHILD_PROPS"] = child_props namespace["ATTR_MAP"] = attr_map namespace["COLLECTOR_PROPERTY"] = collector_property try: tag = namespace["TAG"] except KeyError: tag = None else: try: namespace["TAG"] = tag = normalize_tag(tag) except ValueError: raise TypeError("TAG attribute has incorrect format") if (tag is not None and "DECLARE_NS" not in namespace and not any(hasattr(base, "DECLARE_NS") for base in bases)): if tag[0] is None: namespace["DECLARE_NS"] = {} else: namespace["DECLARE_NS"] = { None: tag[0] } if protect: namespace.setdefault("__slots__", ()) return super().__new__(mcls, name, bases, namespace) def __init__(cls, name, bases, namespace, protect=True): super().__init__(name, bases, namespace) def __setattr__(cls, name, value): try: existing = getattr(cls, name).xq_descriptor except AttributeError: pass else: if isinstance(existing, _PropBase): raise AttributeError("cannot rebind XSO descriptors") if isinstance(value, _PropBase) and cls.__subclasses__(): raise TypeError("adding descriptors is forbidden on classes with" " subclasses (subclasses: {})".format( ", ".join(map(str, cls.__subclasses__())) )) if isinstance(value, Attr): if value.tag in cls.ATTR_MAP: raise TypeError("ambiguous Attr properties") cls.ATTR_MAP[value.tag] = value elif isinstance(value, Text): if cls.TEXT_PROPERTY is not None: raise TypeError("multiple Text properties on XSO class") super().__setattr__("TEXT_PROPERTY", value) elif isinstance(value, (_ChildPropBase, ChildText, ChildTag)): updates = {} for key in value.get_tag_map(): if key in cls.CHILD_MAP: raise TypeError("ambiguous Child properties: {} and {} " "both use the same tag".format( cls.CHILD_MAP[key], value)) updates[key] = value cls.CHILD_MAP.update(updates) cls.CHILD_PROPS.add(value) elif isinstance(value, Collector): if cls.COLLECTOR_PROPERTY is not None: raise TypeError("multiple Collector properties on XSO class") super().__setattr__("COLLECTOR_PROPERTY", value) super().__setattr__(name, value) def __delattr__(cls, name): try: existing = getattr(cls, name).xq_descriptor except AttributeError: pass else: if isinstance(existing, _PropBase): raise AttributeError("cannot unbind XSO descriptors") super().__delattr__(name) def __prepare__(name, bases, **kwargs): return collections.OrderedDict() def parse_events(cls, ev_args, parent_ctx): """ Create an instance of this class, using the events sent into this function. `ev_args` must be the event arguments of the ``"start"`` event. .. seealso:: You probably should not call this method directly, but instead use :class:`XSOParser` with a :class:`SAXDriver`. .. note:: While this method creates an instance of the class, ``__init__`` is not called. See the documentation of :meth:`.xso.XSO` for details. This method is suspendable. """ with parent_ctx as ctx: obj = cls.__new__(cls) attrs = ev_args[2] attr_map = cls.ATTR_MAP.copy() for key, value in attrs.items(): try: prop = attr_map.pop(key) except KeyError: if cls.UNKNOWN_ATTR_POLICY == UnknownAttrPolicy.DROP: continue else: raise ValueError( "unexpected attribute {!r} on {}".format( key, tag_to_str((ev_args[0], ev_args[1])) )) from None try: prop.from_value(obj, value) except: logger.debug("while parsing XSO", exc_info=True) # true means suppress if not obj.xso_error_handler( prop, value, sys.exc_info()): raise for key, prop in attr_map.items(): try: prop.handle_missing(obj, ctx) except: logger.debug("while parsing XSO", exc_info=True) # true means suppress if not obj.xso_error_handler( prop, None, sys.exc_info()): raise try: prop = cls.ATTR_MAP[namespaces.xml, "lang"] except KeyError: pass else: lang = prop.__get__(obj, cls) if lang is not None: ctx.lang = lang collected_text = [] while True: ev_type, *ev_args = yield if ev_type == "end": break elif ev_type == "text": if not cls.TEXT_PROPERTY: if ev_args[0].strip(): # true means suppress if not obj.xso_error_handler( None, ev_args[0], None): raise ValueError("unexpected text") else: collected_text.append(ev_args[0]) elif ev_type == "start": try: handler = cls.CHILD_MAP[ev_args[0], ev_args[1]] except KeyError: if cls.COLLECTOR_PROPERTY: handler = cls.COLLECTOR_PROPERTY.xq_descriptor else: yield from enforce_unknown_child_policy( cls.UNKNOWN_CHILD_POLICY, ev_args, obj.xso_error_handler) continue try: yield from guard( handler.from_events(obj, ev_args, ctx), ev_args ) except: logger.debug("while parsing XSO", exc_info=True) # true means suppress if not obj.xso_error_handler( handler, ev_args, sys.exc_info()): raise if collected_text: collected_text = "".join(collected_text) try: cls.TEXT_PROPERTY.xq_descriptor.from_value( obj, collected_text ) except: logger.debug("while parsing XSO", exc_info=True) # true means suppress if not obj.xso_error_handler( cls.TEXT_PROPERTY.xq_descriptor, collected_text, sys.exc_info()): raise obj.validate() obj.xso_after_load() return obj def register_child(cls, prop, child_cls): """ Register a new :class:`XMLStreamClass` instance `child_cls` for a given :class:`Child` descriptor `prop`. .. warning:: This method cannot be used after a class has been derived from this class. This is for consistency: the method modifies the bookkeeping attributes of the class. There would be two ways to deal with the situation: 1. Updating all the attributes at all the subclasses and re-evaluate the constraints of inheritance. This is simply not implemented, although it would be the preferred way. 2. Only update the bookkeeping attributes on *this* class, hiding the change from any existing subclasses. New subclasses would pick the change up, however, which is inconsistent. This is the way which was previously documented here and is not supported anymore. Obviously, (2) is bad, which is why it is not supported anymore. (1) might be supported at some point in the future. Attempting to use :meth:`register_child` on a class which already has subclasses results in a :class:`TypeError`. Note that *first* using :meth:`register_child` and only *then* deriving clasess is a valid use: it will still lead to a consistent inheritance hierarchy and is a convenient way to break reference cycles (e.g. if an XSO may be its own child). """ if cls.__subclasses__(): raise TypeError( "register_child is forbidden on classes with subclasses" " (subclasses: {})".format( ", ".join(map(str, cls.__subclasses__())) )) if child_cls.TAG in cls.CHILD_MAP: raise ValueError("ambiguous Child") prop.xq_descriptor._register(child_cls) cls.CHILD_MAP[child_cls.TAG] = prop.xq_descriptor # I know it makes only partially sense to have a separate metasubclass for # this, but I like how :meth:`parse_events` is *not* accessible from # instances.
class CapturingXMLStreamClass(XMLStreamClass): """ This is a subclass of :meth:`XMLStreamClass`. It overrides the :meth:`parse_events` to capture the incoming events, including the initial event. .. see:: :class:`CapturingXSO` .. automethod:: parse_events """ def parse_events(cls, ev_args, parent_ctx): """ Capture the events sent to :meth:`.XSO.parse_events`, including the initial `ev_args` to a list and call :meth:`_set_captured_events` on the result of :meth:`.XSO.parse_events`. Like the method it overrides, :meth:`parse_events` is suspendable. """ dest = [("start", )+tuple(ev_args)] result = yield from capture_events( super().parse_events(ev_args, parent_ctx), dest ) result._set_captured_events(dest) return result class XSO(metaclass=XMLStreamClass): """ XSO is short for **X**\ ML **S**\ tream **O**\ bject and means an object which represents a subtree of an XML stream. These objects can also be created and validated on-the-fly from SAX-like events using :class:`XSOParser`. The constructor does not require any arguments and forwards them directly the next class in the resolution order. Note that during deserialization, ``__init__`` is not called. It is assumed that all data is loaded from the XML stream and thus no initialization is required. This is beneficial to applications, as it allows them to define mandatory arguments for ``__init__``. This would not be possible if ``__init__`` was called during deserialization. A way to execute code after successful deserialization is provided through :meth:`xso_after_load`. :class:`XSO` objects support copying. Like with deserialisation, ``__init__`` is not called during copy. The default implementation only copies the XSO descriptors’ values (with deepcopy, they are copied deeply). If you have more attributes to copy, you need to override ``__copy__`` and ``__deepcopy__`` methods. .. versionchanged:: 0.4 Copy and deepcopy support has been added. Previously, copy copied not enough data, while deepcopy copied too much data (including descriptor objects). To declare an XSO, inherit from :class:`XSO` and provide the following attributes on your class: * A ``TAG`` attribute, which is a tuple ``(namespace_uri, localname)`` representing the tag of the XML element you want to match. * An arbitrary number of :class:`Text`, :class:`Collector`, :class:`Child`, :class:`ChildList` and :class:`Attr`-based attributes. .. seealso:: :class:`.xso.model.XMLStreamClass` is the metaclass of :class:`XSO`. The documentation of the metaclass holds valuable information with respect to modifying :class:`XSO` *classes* and subclassing. .. note:: Attributes whose name starts with ``xso_`` or ``_xso_`` are reserved for use by the :mod:`aioxmpp.xso` implementation. Do not use these in your code if you can possibly avoid it. :class:`XSO` subclasses automatically declare a :attr:`~.xso.model.XMLStreamClass.__slots__` attribute which does not include the ``__dict__`` value. This effectively prevents any attributes not declared on the class as descriptors from being written. The rationale is detailed on in the linked documentation. To prevent this from happening in your subclass, inherit with `protect` set to false:: class MyXSO(xso.XSO, protect=False): pass .. versionadded:: 0.6 The handling of the :attr:`~.xso.model.XMLStreamClass.__slots__` attribute was added. To further influence the parsing behaviour of a class, two attributes are provided which give policies for unexpected elements in the XML tree: .. attribute:: UNKNOWN_CHILD_POLICY = UnknownChildPolicy.DROP A value from the :class:`UnknownChildPolicy` enum which defines the behaviour if a child is encountered for which no matching attribute is found. Note that this policy has no effect if a :class:`Collector` descriptor is present, as it takes all children for which no other descriptor exists, thus all children are known. .. attribute:: UNKNOWN_ATTR_POLICY = UnknownAttrPolicy.DROP A value from the :class:`UnknownAttrPolicy` enum which defines the behaviour if an attribute is encountered for which no matching descriptor is found. Example:: class Body(aioxmpp.xso.XSO): TAG = ("jabber:client", "body") text = aioxmpp.xso.Text() class Message(aioxmpp.xso.XSO): TAG = ("jabber:client", "message") UNKNOWN_CHILD_POLICY = aioxmpp.xso.UnknownChildPolicy.DROP type_ = aioxmpp.xso.Attr(tag="type", required=True) from_ = aioxmpp.xso.Attr(tag="from", required=True) to = aioxmpp.xso.Attr(tag="to") id_ = aioxmpp.xso.Attr(tag="id") body = aioxmpp.xso.Child([Body]) Beyond the validation of the individual descriptor values, it is possible to implement more complex validation steps by overriding the :meth:`validate` method: .. automethod:: validate The following methods are available on instances of :class:`XSO`: .. automethod:: unparse_to_sax The following **class methods** are provided by the metaclass: .. automethod:: parse_events(ev_args) .. automethod:: register_child(prop, child_cls) To customize behaviour of deserialization, these methods are provided which can be re-implemented by subclasses: .. automethod:: xso_after_load .. automethod:: xso_error_handler """ UNKNOWN_CHILD_POLICY = UnknownChildPolicy.DROP UNKNOWN_ATTR_POLICY = UnknownAttrPolicy.DROP __slots__ = ("_xso_contents", "__weakref__") def __new__(cls, *args, **kwargs): # XXX: is it always correct to omit the arguments here? # the semantics of the __new__ arguments are odd to say the least result = super().__new__(cls) result._xso_contents = dict() return result def __init__(self, *args, **kwargs): super().__init__(*args, **kwargs) def __copy__(self): result = type(self).__new__(type(self)) result._xso_contents.update(self._xso_contents) return result def __deepcopy__(self, memo): result = type(self).__new__(type(self)) result._xso_contents = { k: copy.deepcopy(v, memo) for k, v in self._xso_contents.items() } return result def validate(self): """ Validate the objects structure beyond the values of individual fields (which have their own validators). This first calls :meth:`_PropBase.validate_contents` recursively on the values of all child descriptors. These may raise (or re-raise) errors which occur during validation of the child elements. To implement your own validation logic in a subclass of :class:`XSO`, override this method and call it via :func:`super` before doing your own validation. Validate is called by the parsing stack after an object has been fully deserialized from the SAX event stream. If the deserialization fails due to invalid values of descriptors or due to validation failures in child objects, this method is obviously not called. """ for descriptor in self.CHILD_PROPS: descriptor.validate_contents(self) def xso_after_load(self): """ After an object has been successfully deserialized, this method is called. Note that ``__init__`` is never called on objects during deserialization. """ def xso_error_handler(self, descriptor, ev_args, exc_info): """ This method is called whenever an error occurs while parsing. If an exception is raised by the parsing function of a descriptor attribute, such as :class:`Attr`, the `descriptor` is passed as first argument, the `exc_info` tuple as third argument and the arguments which led to the descriptor being invoked as second argument. If an unknown child is encountered and the :attr:`UNKNOWN_CHILD_POLICY` is set to :attr:`UnknownChildPolicy.FAIL`, `descriptor` and `exc_info` are passed as :data:`None` and `ev_args` are the arguments to the ``"start"`` event of the child (i.e. a triple ``(namespace_uri, localname, attributes)``). If the error handler wishes to suppress the exception, it must return a true value. Otherwise, the exception is propagated (or a new exception is raised, if the error was not caused by an exception). The error handler may also raise its own exception. .. warning:: Suppressing exceptions can cause invalid input to reside in the object or the object in general being in a state which violates the schema. For example, suppressing exceptions about missing attributes will cause the attribute to remain uninitialized (i.e. left at its :attr:`default` value). Even if the error handler suppresses an exception caused by a broken child, that child will not be added to the object. """ def unparse_to_sax(self, dest): cls = type(self) attrib = {} for prop in cls.ATTR_MAP.values(): prop.to_dict(self, attrib) if cls.DECLARE_NS: for prefix, uri in cls.DECLARE_NS.items(): dest.startPrefixMapping(prefix, uri) dest.startElementNS(self.TAG, None, attrib) try: if cls.TEXT_PROPERTY: cls.TEXT_PROPERTY.to_sax(self, dest) for prop in cls.CHILD_PROPS: prop.to_sax(self, dest) if cls.COLLECTOR_PROPERTY: cls.COLLECTOR_PROPERTY.to_sax(self, dest) finally: dest.endElementNS(self.TAG, None) if cls.DECLARE_NS: for prefix, uri in cls.DECLARE_NS.items(): dest.endPrefixMapping(prefix) def unparse_to_node(self, parent): handler = lxml.sax.ElementTreeContentHandler( makeelement=parent.makeelement) handler.startDocument() handler.startElementNS((None, "root"), None) self.unparse_to_sax(handler) handler.endElementNS((None, "root"), None) handler.endDocument() parent.extend(handler.etree.getroot()) class CapturingXSO(XSO, metaclass=CapturingXMLStreamClass): """ The following **class methods** is provided by the metaclass (which is not publicly available, but a subclass of :class:`~.XMLStreamClass`): .. automethod:: parse_events The :meth:`_set_captured_events` method can be overriden by subclasses to make use of the captured events: .. automethod:: _set_captured_events An example use case for this class is :class:`.disco.InfoQuery`, combined with :mod:`aioxmpp.entitycaps`. We want to be able to store hashes and the generating XML data for use with future versions, including XML data which cannot be parsed by an XSO in the current process (for example, due to an unknown namespace or a plugin which is available but not loaded). With the captured events, it is possible to re-create XML semantically equivalent to the XML originally received. .. versionadded:: 0.5 """ @abc.abstractmethod def _set_captured_events(self, events): """ This method is called by :meth:`parse_events` after parsing the object. `events` is the list of event tuples which this object was deserialised from. Subclasses must override this method. """ class SAXDriver(xml.sax.handler.ContentHandler): """ This is a :class:`xml.sax.handler.ContentHandler` subclass which *only* supports namespace-conforming SAX event sources. `dest_generator_factory` must be a function which returns a new suspendable method supporting the interface of :class:`XSOParser`. The SAX events are converted to an internal event format and sent to the suspendable function in order. `on_emit` may be a callable. Whenever a suspendable function returned by `dest_generator_factory` returns, with the return value as sole argument. When you are done with a :class:`SAXDriver`, you should call :meth:`close` to clean up internal parser state. .. automethod:: close """ def __init__(self, dest_generator_factory, on_emit=None): self._on_emit = on_emit self._dest_factory = dest_generator_factory self._dest = None def _emit(self, value): if self._on_emit: self._on_emit(value) def _send(self, value): if self._dest is None: self._dest = self._dest_factory() self._dest.send(None) try: self._dest.send(value) except StopIteration as err: self._emit(err.value) self._dest = None except: self._dest = None raise def startElementNS(self, name, qname, attributes): uri, localname = name self._send(("start", uri, localname, dict(attributes))) def characters(self, data): self._send(("text", data)) def endElementNS(self, name, qname): self._send(("end",)) def close(self): """ Clean up all internal state. """ if self._dest is not None: self._dest.close() self._dest = None class Context: def __init__(self): super().__init__() self.lang = None def __enter__(self): new_ctx = Context() new_ctx.__dict__ = self.__dict__.copy() return new_ctx def __exit__(self, *args): pass class XSOParser: """ A generic XSO parser which supports a dynamic set of XSOs to parse. :class:`XSOParser` objects are callable and they are suspendable methods (i.e. calling a :class:`XSOParser` returns a generator which parses stanzas from sax-ish events. Use with :class:`SAXDriver`). Example use:: # let Message be a XSO class, like in the XSO example result = None def catch_result(value): nonlocal result result = value parser = aioxmpp.xso.XSOParser() parser.add_class(Message, catch_result) sd = aioxmpp.xso.SAXDriver(parser) lxml.sax.saxify(lmxl.etree.fromstring( "<message id='foo' from='bar' type='chat' />" )) The following methods can be used to dynamically add and remove top-level :class:`XSO` classes. .. automethod:: add_class .. automethod:: remove_class .. automethod:: get_tag_map """ def __init__(self): self._class_map = {} self._tag_map = {} def add_class(self, cls, callback): """ Add a class `cls` for parsing as root level element. When an object of `cls` type has been completely parsed, `callback` is called with the object as argument. """ if cls.TAG in self._tag_map: raise ValueError( "duplicate tag: {!r} is already handled by {}".format( cls.TAG, self._tag_map[cls.TAG])) self._class_map[cls] = callback self._tag_map[cls.TAG] = (cls, callback) def get_tag_map(self): """ Return the internal mapping which maps tags to tuples of ``(cls, callback)``. .. warning:: The results of modifying this dict are undefined. Make a copy if you need to modify the result of this function. """ return self._tag_map def get_class_map(self): """ Return the internal mapping which maps classes to the associated callbacks. .. warning:: The results of modifying this dict are undefined. Make a copy if you need to modify the result of this function. """ return self._class_map def remove_class(self, cls): """ Remove a XSO class `cls` from parsing. This method raises :class:`KeyError` with the classes :attr:`TAG` attribute as argument if removing fails because the class is not registered. """ del self._tag_map[cls.TAG] del self._class_map[cls] def __call__(self): ctx = Context() while True: ev_type, *ev_args = yield if ev_type == "text" and not ev_args[0].strip(): continue tag = ev_args[0], ev_args[1] try: cls, cb = self._tag_map[tag] except KeyError: raise UnknownTopLevelTag( "unhandled top-level element", ev_args) cb((yield from cls.parse_events(ev_args, ctx))) def drop_handler(ev_args): depth = 1 while depth: ev = yield if ev[0] == "start": depth += 1 elif ev[0] == "end": depth -= 1 def enforce_unknown_child_policy(policy, ev_args, error_handler=None): if policy == UnknownChildPolicy.DROP: yield from drop_handler(ev_args) else: if error_handler is not None: if error_handler(None, ev_args, None): yield from drop_handler(ev_args) return raise ValueError("unexpected child") def guard(dest, ev_args): next(dest) depth = 1 while True: ev = yield if ev[0] == "start": depth += 1 elif ev[0] == "end": depth -= 1 try: dest.send(ev) except StopIteration as exc: return exc.value except Exception as exc: error = exc break while depth > 0: ev_type, *_ = yield if ev_type == "end": depth -= 1 raise error def lang_attr(instance, ctx): """ A `missing` handler for :class:`Attr` descriptors. If any parent object has a ``xml:lang`` attribute set, its value is used. Pass as `missing` argument to :class:`Attr` constructors to use this behaviour for a given attribute. """ return ctx.lang def capture_events(receiver, dest): """ Capture all events sent to `receiver` in the sequence `dest`. This is a generator, and it is best used with ``yield from``. The observable effect of using this generator with ``yield from`` is identical to the effect of using `receiver` with ``yield from`` directly (including the return value), but in addition, the values which are *sent* to the receiver are captured in `dest`. If `receiver` raises an exception or the generator is closed prematurely using its :meth:`close`, `dest` is cleared. This is used to implement :class:`CapturingXSO`. See the documentation there for use cases. .. versionadded:: 0.5 """ # the following code is a copy of the formal definition of `yield from` # in PEP 380, with modifications to capture the value sent during yield _i = iter(receiver) try: _y = next(_i) except StopIteration as _e: return _e.value try: while True: try: _s = yield _y except GeneratorExit as _e: try: _m = _i.close except AttributeError: pass else: _m() raise _e except BaseException as _e: _x = sys.exc_info() try: _m = _i.throw except AttributeError: raise _e else: try: _y = _m(*_x) except StopIteration as _e: _r = _e.value break else: dest.append(_s) try: if _s is None: _y = next(_i) else: _y = _i.send(_s) except StopIteration as _e: _r = _e.value break except: dest.clear() raise return _r def events_to_sax(events, dest): """ Convert an iterable `events` of XSO events to SAX events by calling the matching SAX methods on `dest` """ name_stack = [] for ev_type, *ev_args in events: if ev_type == "start": name = (ev_args[0], ev_args[1]) dest.startElementNS(name, None, ev_args[2]) name_stack.append(name) elif ev_type == "end": name = name_stack.pop() dest.endElementNS(name, None) elif ev_type == "text": dest.characters(ev_args[0])