# # Copyright (c), 2018-2026, SISSA (International School for Advanced Studies). # All rights reserved. # This file is distributed under the terms of the MIT License. # See the file 'LICENSE' in the root directory of the present # distribution, or http://opensource.org/licenses/MIT. # # @author Davide Brunato # """ XPath 2.0 implementation - part 1 (parser class and symbols) """ import copy from abc import ABCMeta import locale from collections.abc import Callable, MutableMapping from urllib.parse import urlparse from typing import Any, ClassVar, cast import elementpath.aliases as ta from elementpath.helpers import upper_camel_case, is_ncname from elementpath.exceptions import ElementPathTypeError, ElementPathValueError, xpath_error from elementpath.namespaces import XML_NAMESPACE, XSD_NAMESPACE, XPATH_FUNCTIONS_NAMESPACE, \ XQT_ERRORS_NAMESPACE, XSD_NOTATION, XSD_ANY_ATOMIC_TYPE from elementpath.namespaces import get_prefixed_name from elementpath.datatypes import QName, builtin_atomic_types from elementpath.collations import UNICODE_COLLATION_BASE_URI, UNICODE_CODEPOINT_COLLATION from elementpath.xpath_tokens import XPathToken, ProxyToken, XPathFunction, \ XPathConstructor, SchemaConstructor, ExternalFunction from elementpath.sequence_types import get_function_signatures, is_sequence_type, \ match_sequence_type from elementpath.schema_proxy import AbstractSchemaProxy from elementpath.xpath1 import XPath1Parser class XPath2Parser(XPath1Parser): """ XPath 2.0 expression parser class. This is the default parser used by XPath selectors. A parser instance represents also the XPath static context. With *variable_types* you can pass a dictionary with the types of the in-scope variables. Provide a *namespaces* dictionary argument for mapping namespace prefixes to URI inside expressions. If *strict* is set to `False` the parser enables also the parsing of QNames, like the ElementPath library. There are some additional XPath 2.0 related arguments. :param namespaces: a dictionary with mapping from namespace prefixes into URIs. :param variable_types: a dictionary with the static context's in-scope variable \ types. It defines the associations between variables and static types. :param strict: if strict mode is `False` the parser enables parsing of QNames, \ like the ElementPath library. Default is `True`. :param compatibility_mode: if set to `True` the parser instance works with \ XPath 1.0 compatibility rules. :param default_namespace: the default namespace to apply to unprefixed names. \ For default no namespace is applied (empty namespace ''). :param function_namespace: the default namespace to apply to unprefixed function \ names. For default the namespace "http://www.w3.org/2005/xpath-functions" is used. :param schema: the schema proxy class or instance to use for types, attributes and \ elements lookups. If an `AbstractSchemaProxy` subclass is provided then a schema \ proxy instance is built without the optional argument, that involves a mapping of \ only XSD builtin types. If it's not provided the XPath 2.0 schema's related \ expressions cannot be used. :param base_uri: an absolute URI maybe provided, used when necessary in the \ resolution of relative URIs. :param default_collation: the default string collation to use. If not set the \ environment's default locale setting is used. :param document_types: statically known documents, that is a dictionary from \ absolute URIs onto types. Used for type check when calling the *fn:doc* function \ with a sequence of URIs. The default type of a document is 'document-node()'. :param collection_types: statically known collections, that is a dictionary from \ absolute URIs onto types. Used for type check when calling the *fn:collection* \ function with a sequence of URIs. The default type of a collection is 'node()*'. :param default_collection_type: this is the type of the sequence of nodes that \ would result from calling the *fn:collection* function with no arguments. \ Default is 'node()*'. """ version = '2.0' DEFAULT_NAMESPACES: ClassVar[dict[str, str]] = { 'xml': XML_NAMESPACE, 'xs': XSD_NAMESPACE, 'fn': XPATH_FUNCTIONS_NAMESPACE, 'err': XQT_ERRORS_NAMESPACE } PATH_STEP_LABELS = ('axis', 'function', 'kind test') PATH_STEP_SYMBOLS = { '(integer)', '(string)', '(float)', '(decimal)', '(name)', '*', '@', '..', '.', '(', '{' } # https://www.w3.org/TR/xpath20/#id-reserved-fn-names RESERVED_FUNCTION_NAMES = { 'attribute', 'comment', 'document-node', 'element', 'empty-sequence', 'if', 'item', 'node', 'processing-instruction', 'schema-attribute', 'schema-element', 'text', 'typeswitch', } function_signatures: dict[tuple[QName, int], str] = XPath1Parser.function_signatures.copy() namespaces: dict[str, str] token: XPathToken next_token: XPathToken def __init__(self, namespaces: ta.NamespacesType | None = None, strict: bool = True, compatibility_mode: bool = False, default_collation: str | None = None, default_namespace: str | None = None, function_namespace: str | None = None, xsd_version: str | None = None, schema: AbstractSchemaProxy | None = None, base_uri: str | None = None, variable_types: dict[str, str] | None = None, document_types: dict[str, str] | None = None, collection_types: ta.NamespacesType | None = None, default_collection_type: str = 'node()*') -> None: super(XPath2Parser, self).__init__(namespaces, strict) self.compatibility_mode = compatibility_mode if default_collation is not None: self.default_collation = default_collation else: # Obtain the current collation locale using setlocale() with `None`. # Consider only configured UTF-8 encodings, otherwise keep Unicode # Codepoint Collation. _locale = locale.setlocale(locale.LC_COLLATE, None) if '.' in _locale: language_code, encoding = _locale.split('.') if encoding.lower() == 'utf-8': self.default_collation = f'{UNICODE_COLLATION_BASE_URI}?lang={language_code}' self._xsd_version = xsd_version if xsd_version is not None else '1.0' if default_namespace is not None: self.default_namespace = self.namespaces[''] = default_namespace else: self.default_namespace = self.namespaces.get('', '') if function_namespace is not None: self.function_namespace = function_namespace if schema is None: pass elif not isinstance(schema, AbstractSchemaProxy): msg = "argument 'schema' must be an instance of AbstractSchemaProxy" raise ElementPathTypeError(msg) else: schema.bind_parser(self) if not variable_types: self.variable_types = {} elif all(is_sequence_type(v, self) for v in variable_types.values()): self.variable_types = variable_types.copy() else: raise ElementPathValueError('invalid sequence type for in-scope variable types') self.base_uri = None if base_uri is None else urlparse(base_uri).geturl() if document_types: if any(not is_sequence_type(v, self) for v in document_types.values()): raise ElementPathValueError('invalid sequence type in document_types argument') self.document_types = document_types if collection_types: if any(not is_sequence_type(v, self) for v in collection_types.values()): raise ElementPathValueError('invalid sequence type in collection_types argument') self.collection_types = collection_types if not is_sequence_type(default_collection_type, self): raise ElementPathValueError('invalid sequence type for ' 'default_collection_type argument') self.default_collection_type = default_collection_type def __str__(self) -> str: args = [] if self.compatibility_mode: args.append('compatibility_mode=True') if self.default_collation != UNICODE_CODEPOINT_COLLATION: args.append(f'default_collation={self.default_collation!r}') if self.function_namespace != XPATH_FUNCTIONS_NAMESPACE: args.append(f'function_namespace={self.function_namespace!r}') if self._xsd_version != '1.0': args.append(f'xsd_version={self._xsd_version!r}') if self.schema is not None: args.append(f'schema={self.schema!r}') if self.base_uri is not None: args.append(f'base_uri={self.base_uri!r}') if self.variable_types: args.append(f'variable_types={self.variable_types!r}') if self.document_types: args.append(f'document_types={self.document_types!r}') if self.collection_types: args.append(f'collection_types={self.collection_types!r}') if self.default_collection_type != 'node()*': args.append(f'default_collection_type={self.default_collection_type!r}') if not args: return super().__str__() repr_string = super().__str__()[:-1] if repr_string.endswith('('): return f"{repr_string}{', '.join(args)})" return f"{repr_string}, {', '.join(args)})" def __getstate__(self) -> dict[str, Any]: state = self.__dict__.copy() state.pop('symbol_table', None) state.pop('tokenizer', None) return state @property def xsd_version(self) -> str: if self.schema is None: return self._xsd_version try: return self.schema.xsd_version except (AttributeError, NotImplementedError): return self._xsd_version def advance(self, *symbols: str, message: str | None = None) -> XPathToken: super(XPath2Parser, self).advance(*symbols, message=message) if self.next_token.symbol == '(:': # Parses and consumes an XPath 2.0 comment. A comment is delimited # by symbols '(:' and ':)' and can be nested. The current token is # saved and restored after parsing the entire comment. Comments # cannot be inside a prefixed name ':' specification. self.token.unexpected(':') token = self.token comment_level = 1 while comment_level: self.advance_until('(:', ':)') if self.next_token.symbol == ':)': comment_level -= 1 else: comment_level += 1 self.advance(':)') self.next_token.unexpected(':') self.token = token return self.token @classmethod def constructor(cls, symbol: str, bp: int = 90, nargs: ta.NargsType = 1, sequence_types: tuple[()] | tuple[str, ...] | list[str] = (), label: str | tuple[str, ...] = 'constructor function') \ -> Callable[[Callable[..., Any]], Callable[..., Any]]: """ Statically creates a constructor token class, that is registered in the globals of the module where the method is called. """ if not sequence_types: assert nargs == 1 sequence_types = ('xs:anyAtomicType?', 'xs:%s?' % symbol) type_name = f'{{{XSD_NAMESPACE}}}{symbol}' kwargs = { 'bases': (XPathConstructor,), 'label': label, 'nargs': nargs, 'lbp': bp, 'rbp': bp, 'sequence_types': sequence_types, 'name': type_name, 'type_class': builtin_atomic_types.get(type_name), } token_class = cls.register(symbol, **kwargs) def bind(func: Callable[..., Any]) -> Callable[..., Any]: method_name = func.__name__.partition('_')[0] if method_name != 'cast': raise ValueError("The function name must be 'cast' or starting with 'cast_'") setattr(token_class, method_name, func) return func return bind def _register(self, symbol: str, class_name: str, **kwargs: Any) \ -> type[ta.XPathTokenType]: """ Register/update a token class in the symbol table of a parser instance. :param symbol: The identifier symbol for the new class. :param class_name: The name of the new class. :param kwargs: Optional attributes/methods for the token class. :return: A token class. """ kwargs['symbol'] = symbol if 'lookup_name' not in kwargs: lookup_name = kwargs['lookup_name'] = symbol else: lookup_name = kwargs['lookup_name'] if 'label' not in kwargs: kwargs['label'] = 'symbol' token_class_bases = kwargs.get('bases', (self.token_base_class,)) kwargs.update({ '__module__': self.__module__, '__qualname__': class_name, '__return__': None }) token_class = cast( type[ta.XPathTokenType], cast(object, ABCMeta(class_name, token_class_bases, kwargs)) ) if self.symbol_table is self.__class__.symbol_table: self.symbol_table = copy.copy(self.symbol_table) self.symbol_table[lookup_name] = token_class self.tokenizer = None return token_class def schema_constructor(self, atomic_type_name: str, bp: int = 90) -> type[XPathFunction]: """ Dynamically register a token class for a schema atomic type constructor function. """ if atomic_type_name in (XSD_ANY_ATOMIC_TYPE, XSD_NOTATION): raise xpath_error('XPST0080') symbol = get_prefixed_name(atomic_type_name, self.namespaces) class_name = "_%sConstructorFunction" % symbol.replace(':', '_') kwargs = { 'bases': (SchemaConstructor,), 'name': atomic_type_name, 'nargs': 1, 'label': 'constructor function', 'pattern': r'\b%s(?=\s*\(|\s*\(\:.*\:\)\()' % symbol, 'lbp': bp, 'rbp': bp, } return cast(type[XPathFunction], self._register(symbol, class_name, **kwargs)) def external_function(self, callback: Callable[..., Any], name: str | None = None, prefix: str | None = None, sequence_types: tuple[str, ...] = (), bp: int = 90) -> type[XPathFunction]: """Registers a token class for an external function.""" import inspect symbol = name or callback.__name__ if not is_ncname(symbol): raise ElementPathValueError(f'{symbol!r} is not a name') elif symbol in self.RESERVED_FUNCTION_NAMES: raise ElementPathValueError(f'{symbol!r} is a reserved function name') nargs: ta.NargsType spec = inspect.getfullargspec(callback) if spec.varargs is not None: if spec.args: nargs = len(spec.args), None else: nargs = None elif spec.defaults is None: nargs = len(spec.args) else: nargs = len(spec.args) - len(spec.defaults), len(spec.args) if prefix: namespace = self.namespaces[prefix] qname = QName(namespace, f'{prefix}:{symbol}') else: namespace = XPATH_FUNCTIONS_NAMESPACE qname = QName(XPATH_FUNCTIONS_NAMESPACE, f'fn:{symbol}') function_signatures = get_function_signatures(qname, nargs, sequence_types) if qname.expanded_name in self.symbol_table: msg = f'function {qname.qname!r} is already registered' raise ElementPathValueError(msg) elif symbol not in self.symbol_table: lookup_name = symbol else: lookup_name = qname.expanded_name token_class = self.symbol_table[symbol] if issubclass(token_class, ProxyToken): pass elif namespace == token_class.namespace: msg = f'function {qname.qname!r} is already registered' raise ElementPathValueError(msg) elif not issubclass(token_class, XPathFunction) \ or token_class.label == 'kind test': msg = f'{symbol!r} name collides with {token_class!r}' raise ElementPathValueError(msg) else: # Register a new proxy token, moving the already present token class to # qualified name. self.symbol_table[f'{{{token_class.namespace}}}{symbol}'] = token_class class_name = f'{upper_camel_case(qname.local_name)}FunctionProxy' kwargs = { 'bases': (ProxyToken,), 'label': 'function', 'lbp': bp, 'rbp': bp, } self._register(symbol, class_name, **kwargs) class_name = f'{upper_camel_case(qname.qname)}ExternalFunction' kwargs = { 'lookup_name': lookup_name, 'bases': (ExternalFunction,), 'namespace': namespace, 'label': 'external function', 'nargs': nargs, 'lbp': bp, 'rbp': bp, 'sequence_types': sequence_types, 'callback': staticmethod(callback), } token_class = self._register(symbol, class_name, **kwargs) if function_signatures: # Register function signatures if self.function_signatures is self.__class__.function_signatures: self.function_signatures = dict(self.__class__.function_signatures) self.function_signatures.update(function_signatures) return cast(type[XPathFunction], token_class) def is_schema_bound(self) -> bool: return self.schema is not None and 'symbol_table' in self.__dict__ def check_variables(self, values: MutableMapping[str, Any]) -> None: if self.variable_types is None: return for varname, xsd_type in self.variable_types.items(): if varname not in values: raise xpath_error('XPST0008', "missing variable {!r}".format(varname)) for varname, value in values.items(): try: sequence_type = self.variable_types[varname] except KeyError: sequence_type = 'item()*' if isinstance(value, list) else 'item()' if not match_sequence_type(value, sequence_type, self): message = "Unmatched sequence type for variable {!r}".format(varname) raise xpath_error('XPDY0050', message) ## # Remove symbols that have to be redefined for XPath 2.0. XPath2Parser.unregister(',') XPath2Parser.unregister('(') XPath2Parser.unregister('contains') XPath2Parser.unregister('lang') XPath2Parser.unregister('id') XPath2Parser.unregister('substring-before') XPath2Parser.unregister('substring-after') XPath2Parser.unregister('starts-with') ### # Symbols XPath2Parser.register('?') XPath2Parser.register('(:') XPath2Parser.register(':)') # XPath 2.0 definitions continue into module xpath2_operators