"""syntaxtree.py - syntax tree classes and transformation functions for converting the concrete into the abstract syntax tree for DHParser Copyright 2016 by Eckhart Arnold (arnold@badw.de) Bavarian Academy of Sciences an Humanities (badw.de) Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License. """ import abc import copy import inspect import itertools import os from functools import partial, singledispatch try: import regex as re except ImportError: import re from .typing import AbstractSet, Any, ByteString, Callable, cast, Container, Iterator, List, \ NamedTuple, Sequence, Union, Text, Tuple from DHParser.toolkit import log_dir, expand_table, line_col, smart_list __all__ = ['WHITESPACE_PTYPE', 'TOKEN_PTYPE', 'ZOMBIE_PARSER', 'ParserBase', 'Error', 'Node', 'TransformationFunc', 'transformation_factory', 'key_parser_name', 'key_tag_name', 'traverse', 'no_transformation', 'replace_by_single_child', 'reduce_single_child', 'replace_parser', 'is_whitespace', 'is_empty', 'is_expendable', 'is_token', 'remove_children_if', 'remove_whitespace', 'remove_expendables', 'remove_tokens', 'flatten', 'remove_enclosing_delimiters', 'forbid', 'require', 'assert_content'] class ParserBase: """ ParserBase is the base class for all real and mock parser classes. It is defined here, because Node objects require a parser object for instantiation. """ def __init__(self, name=''): # , pbases=frozenset()): self.name = name # type: str self._ptype = ':' + self.__class__.__name__ # type: str def __str__(self): return self.name or self.ptype @property def ptype(self) -> str: return self._ptype class MockParser(ParserBase): """ MockParser objects can be used to reconstruct syntax trees from a serialized form like S-expressions or XML. Mock objects can mimic different parser types by assigning them a ptype on initialization. Mock objects should not be used for anything other than syntax tree (re-)construction. In all other cases where a parser object substitute is needed, chose the singleton ZOMBIE_PARSER. """ def __init__(self, name='', ptype=''): # , pbases=frozenset()): assert not ptype or ptype[0] == ':' super(MockParser, self).__init__(name) self.name = name self._ptype = ptype or ':' + self.__class__.__name__ def __str__(self): return self.name or self.ptype class ZombieParser(MockParser): """ Serves as a substitute for a Parser instance. ``ZombieParser`` is the class of the singelton object ``ZOMBIE_PARSER``. The ``ZOMBIE_PARSER`` has a name and can be called, but it never matches. It serves as a substitute where only these (or one of these properties) is needed, but no real Parser- object is instantiated. """ alive = False def __init__(self): super(ZombieParser, self).__init__("__ZOMBIE__") assert not self.__class__.alive, "There can be only one!" assert self.__class__ == ZombieParser, "No derivatives, please!" self.__class__.alive = True def __copy__(self): return self def __deepcopy__(self, memo): return self def __call__(self, text): """Better call Saul ;-)""" return None, text ZOMBIE_PARSER = ZombieParser() # # Python 3.6: # class Error(NamedTuple): # pos: int # msg: str Error = NamedTuple('Error', [('pos', int), ('msg', str)]) StrictResultType = Union[Tuple['Node', ...], str] ResultType = Union[Tuple['Node', ...], 'Node', str, None] class Node: """ Represents a node in the concrete or abstract syntax tree. Attributes: tag_name (str): The name of the node, which is either its parser's name or, if that is empty, the parser's class name result (str or tuple): The result of the parser which generated this node, which can be either a string or a tuple of child nodes. children (tuple): The tuple of child nodes or an empty tuple if there are no child nodes. READ ONLY! parser (Parser): The parser which generated this node. WARNING: In case you use mock syntax trees for testing or parser replacement during the AST-transformation: DO NOT rely on this being a real parser object in any phase after parsing (i.e. AST-transformation and compiling), for example by calling ``isinstance(node.parer, ...)``. errors (list): A list of parser- or compiler-errors: tuple(position, string) attached to this node len (int): The full length of the node's string result if the node is a leaf node or, otherwise, the concatenated string result's of its descendants. The figure always represents the length before AST-transformation ans will never change through AST-transformation. READ ONLY! pos (int): the position of the node within the parsed text. The value of ``pos`` is -1 meaning invalid by default. Setting this value will set the positions of all child nodes relative to this value. To set the pos values of all nodes in a syntax tree, the pos value of the root node should be set to 0 right after parsing. Other than that, this value should be considered READ ONLY. At any rate, it should only be reassigned only during parsing stage and never during or after the AST-transformation. """ def __init__(self, parser, result: ResultType) -> None: """Initializes the ``Node``-object with the ``Parser``-Instance that generated the node and the parser's result. """ self._result = '' # type: StrictResultType self._errors = [] # type: List[str] self._children = () # type: Tuple['Node', ...] self.result = result self._len = len(self.result) if not self.children else \ sum(child._len for child in self.children) # type: int # self.pos: int = 0 # continuous updating of pos values self._pos = -1 # type: int self.parser = parser or ZOMBIE_PARSER self.error_flag = any(r.error_flag for r in self.children) \ if self.children else False # type: bool def __str__(self): if self.children: return "".join(str(child) for child in self.children) return str(self.result) def __repr__(self): mpargs = {'name': self.parser.name, 'ptype': self.parser.ptype} parg = "MockParser({name}, {ptype})".format(**mpargs) rarg = str(self) if not self.children else \ "(" + ", ".join(repr(child) for child in self.children) + ")" return "Node(%s, %s)" % (parg, rarg) def __eq__(self, other): # return str(self.parser) == str(other.parser) and self.result == other.result return self.tag_name == other.tag_name and self.result == other.result def __hash__(self): return hash(self.tag_name) def __deepcopy__(self, memodict={}): result = copy.deepcopy(self.result) other = Node(self.parser, result) other._pos = self._pos return other @property # this needs to be a (dynamic) property, in case sef.parser gets updated def tag_name(self) -> str: return self.parser.name or self.parser.ptype # ONLY FOR DEBUGGING: return self.parser.name + ':' + self.parser.ptype @property def result(self) -> StrictResultType: return self._result @result.setter def result(self, result: ResultType): # # made obsolete by static type checking with mypy is done # assert ((isinstance(result, tuple) and all(isinstance(child, Node) for child in result)) # or isinstance(result, Node) # or isinstance(result, str)), str(result) self._result = (result,) if isinstance(result, Node) else result or '' self._children = cast(Tuple['Node', ...], self._result) \ if isinstance(self._result, tuple) else cast(Tuple['Node', ...], ()) @property def children(self) -> Tuple['Node', ...]: return self._children @property def len(self) -> int: # DEBUGGING: print(self.tag_name, str(self.pos), str(self._len), str(self)[:10].replace('\n','.')) return self._len @property def pos(self) -> int: assert self._pos >= 0, "position value not initialized!" return self._pos @pos.setter def pos(self, pos: int): # assert isinstance(pos, int) self._pos = pos offset = 0 for child in self.children: child.pos = pos + offset offset += child.len @property def errors(self) -> List[Error]: return [Error(self.pos, err) for err in self._errors] def show(self) -> str: """Returns content as string, inserting error messages where errors ocurred. """ s = "".join(child.show_errors() for child in self.children) if self.children \ else str(self.result) return (' <<< Error on "%s" | %s >>> ' % (s, '; '.join(self._errors))) if self._errors else s def _tree_repr(self, tab, openF, closeF, dataF=lambda s: s) -> str: """ Generates a tree representation of this node and its children in string from. The kind ot tree-representation that is determined by several function parameters. This could be an XML-representation or a lisp-like S-expression. Args: tab (str): The indentation string, e.g. '\t' or ' ' openF: (Node->str) A function that returns an opening string (e.g. an XML-tag_name) for a given node closeF: (Node->str) A function that returns a closeF string (e.g. an XML-tag_name) for a given node. dataF: (str->str) A function that filters the data string before printing, e.g. to add quotation marks Returns (str): A string that contains a (serialized) tree representation of the node and its children. """ head = openF(self) tail = closeF(self) if not self.result: return head + tail head = head + '\n' # place the head, tail and content tail = '\n' + tail # of the node on different lines if self.children: content = [] for child in self.children: subtree = child._tree_repr(tab, openF, closeF, dataF).split('\n') content.append('\n'.join((tab + s) for s in subtree)) return head + '\n'.join(content) + tail res = cast(str, self.result) # safe, because if there are no children, result is a string if head[0] == "<" and res.find('\n') < 0: # for XML: place tags for leaf-nodes on one line if possible return head[:-1] + self.result + tail[1:] else: return head + '\n'.join([tab + dataF(s) for s in res.split('\n')]) + tail def as_sexpr(self, src: str=None) -> str: """ Returns content as S-expression, i.e. in lisp-like form. Args: src: The source text or `None`. In case the source text is given the position of the element in the text will be reported as line and column. """ def opening(node) -> str: s = '(' + node.tag_name # s += " '(pos %i)" % node.pos if src: s += " '(pos %i " % node.pos + " %i %i)" % line_col(src, node.pos) if node.errors: s += " '(err '(%s))" % ' '.join(str(err).replace('"', r'\"') for err in node.errors) return s def pretty(s): return '"%s"' % s if s.find('"') < 0 \ else "'%s'" % s if s.find("'") < 0 \ else '"%s"' % s.replace('"', r'\"') return self._tree_repr(' ', opening, lambda node: ')', pretty) def as_xml(self, src: str=None) -> str: """ Returns content as XML-tree. Args: src: The source text or `None`. In case the source text is given the position will also be reported as line and column. """ def opening(node) -> str: s = '<' + node.tag_name # s += ' pos="%i"' % node.pos if src: s += ' line="%i" col="%i"' % line_col(src, node.pos) if node.errors: s += ' err="%s"' % ''.join(str(err).replace('"', r'\"') for err in node.errors) s += ">" return s def closing(node): s = '' return s return self._tree_repr(' ', opening, closing) def add_error(self, error_str) -> 'Node': self._errors.append(error_str) self.error_flag = True return self def propagate_error_flags(self) -> None: """Recursively propagates error flags set on child nodes to its parents. This can be used if errors are added to descendant nodes after syntaxtree construction, i.e. in the compile phase. """ for child in self.children: child.propagate_error_flags() self.error_flag |= child.error_flag def collect_errors(self, clear_errors=False) -> List[Error]: """ Returns all errors of this node or any child node in the form of a set of tuples (position, error_message), where position is always relative to this node. """ errors = self.errors if clear_errors: self._errors = [] self.error_flag = False if self.children: for child in self.children: errors.extend(child.collect_errors(clear_errors)) return errors def log(self, log_file_name): st_file_name = log_file_name with open(os.path.join(log_dir(), st_file_name), "w", encoding="utf-8") as f: f.write(self.as_sexpr()) def find(self, match_function) -> Iterator['Node']: """Finds nodes in the tree that match a specific criterion. ``find`` is a generator that yields all nodes for which the given ``match_function`` evaluates to True. The tree is traversed pre-order. Args: match_function (function): A function that takes as Node object as argument and returns True or False Yields: Node: all nodes of the tree for which ``match_function(node)`` returns True """ if match_function(self): yield self else: for child in self.children: for nd in child.find(match_function): yield nd # def range(self, match_first, match_last): # """Iterates over the range of nodes, starting from the first # node for which ``match_first`` becomes True until the first node # after this one for which ``match_last`` becomes true or until # the end if it never does. # # Args: # match_first (function): A function that takes as Node # object as argument and returns True or False # match_last (function): A function that takes as Node # object as argument and returns True or False # Yields: # Node: all nodes of the tree for which # ``match_function(node)`` returns True # """ # def navigate(self, path): # """Yields the results of all descendant elements matched by # ``path``, e.g. # 'd/s' yields 'l' from (d (s l)(e (r x1) (r x2)) # 'e/r' yields 'x1', then 'x2' # 'e' yields (r x1)(r x2) # # Args: # path (str): The path of the object, e.g. 'a/b/c'. The # components of ``path`` can be regular expressions # # Returns: # The object at the path, either a string or a Node or # ``None``, if the path did not match. # """ # def nav(node, pl): # if pl: # return itertools.chain(nav(child, pl[1:]) for child in node.children # if re.match(pl[0], child.tag_name)) # else: # return self.result, # return nav(path.split('/')) ######################################################################## # # syntax tree transformation functions # ######################################################################## TransformationFunc = Union[Callable[[Node], Any], partial] def transformation_factory(t=None): """Creates factory functions from transformation-functions that dispatch on the first parameter after the node parameter. Decorating a transformation-function that has more than merely the ``node``-parameter with ``transformation_factory`` creates a function with the same name, which returns a partial-function that takes just the node-parameter. Additionally, there is some some syntactic sugar for transformation-functions that receive a collection as their second parameter and do not have any further parameters. In this case a list of parameters passed to the factory function will be converted into a collection. Main benefit is readability of processing tables. Usage: @transformation_factory(AbtractSet[str]) def remove_tokens(node, tokens): ... or, alternatively: @transformation_factory def remove_tokens(node, tokens: AbstractSet[str]): ... Example: trans_table = { 'expression': remove_tokens('+', '-') } instead of: trans_table = { 'expression': partial(remove_tokens, tokens={'+', '-'}) } """ def decorator(f): sig = inspect.signature(f) params = list(sig.parameters.values())[1:] if len(params) == 0: return f # '@transformer' not needed w/o free parameters assert t or params[0].annotation != params[0].empty, \ "No type information on second parameter found! Please, use type " \ "annotation or provide the type information via transfomer-decorator." p1type = t or params[0].annotation f = singledispatch(f) if len(params) == 1 and issubclass(p1type, Container) and not issubclass(p1type, Text) \ and not issubclass(p1type, ByteString): def gen_special(*args): c = set(args) if issubclass(p1type, AbstractSet) else \ list(args) if issubclass(p1type, Sequence) else args d = {params[0].name: c} return partial(f, **d) f.register(p1type.__args__[0], gen_special) def gen_partial(*args, **kwargs): d = {p.name: arg for p, arg in zip(params, args)} d.update(kwargs) return partial(f, **d) f.register(p1type, gen_partial) return f if isinstance(t, type(lambda: 1)): # Provide for the case that transformation_factory has been # written as plain decorator and not as a function call that # returns the decorator proper. func = t; t = None return decorator(func) else: return decorator WHITESPACE_PTYPE = ':Whitespace' TOKEN_PTYPE = ':Token' def key_parser_name(node) -> str: return node.parser.name def key_tag_name(node) -> str: return node.tag_name def traverse(root_node, processing_table, key_func=key_tag_name) -> None: """Traverses the snytax tree starting with the given ``node`` depth first and applies the sequences of callback-functions registered in the ``calltable``-dictionary. The most important use case is the transformation of a concrete syntax tree into an abstract tree (AST). But it is also imaginable to employ tree-traversal for the semantic analysis of the AST. In order to assign sequences of callback-functions to nodes, a dictionary ("processing table") is used. The keys usually represent tag names, but any other key function is possible. There exist three special keys: '+': always called (before any other processing function) '*': called for those nodes for which no (other) processing function appears in the table '~': always called (after any other processing function) Args: root_node (Node): The root-node of the syntax tree to be traversed processing_table (dict): node key -> sequence of functions that will be applied to matching nodes in order. This dictionary is interpreted as a ``compact_table``. See ``toolkit.expand_table`` or ``EBNFCompiler.EBNFTransTable`` key_func (function): A mapping key_func(node) -> keystr. The default key_func yields node.parser.name. Example: table = { "term": [replace_by_single_child, flatten], "factor, flowmarker, retrieveop": replace_by_single_child } traverse(node, table) """ # commented, because this approach is too error prone! # def funclist(call): # return [as_partial(func) for func in smart_list(call)] # normalize processing_table entries by turning single values into lists # with a single value table = {name: smart_list(call) for name, call in list(processing_table.items())} table = expand_table(table) cache = {} def traverse_recursive(node): if node.children: for child in node.result: traverse_recursive(child) # depth first node.error_flag |= child.error_flag # propagate error flag key = key_func(node) sequence = cache.get(key, None) if sequence is None: sequence = table.get('+', []) + \ table.get(key, table.get('*', [])) + \ table.get('~', []) # '+' always called (before any other processing function) # '*' called for those nodes for which no (other) processing function # appears in the table # '~' always called (after any other processing function) cache[key] = sequence for call in sequence: call(node) traverse_recursive(root_node) def no_transformation(node): pass # ------------------------------------------------ # # rearranging transformations: # - tree may be rearranged (e.g.flattened) # - nodes that are not leaves may be dropped # - order is preserved # - all leaves are kept # # ------------------------------------------------ def replace_by_single_child(node): """Remove single branch node, replacing it by its immediate descendant. (In case the descendant's name is empty (i.e. anonymous) the name of this node's parser is kept.) """ if node.children and len(node.result) == 1: if not node.result[0].parser.name: node.result[0].parser.name = node.parser.name node.parser = node.result[0].parser node._errors.extend(node.result[0].errors) node.result = node.result[0].result def reduce_single_child(node): """Reduce a single branch node, by transferring the result of its immediate descendant to this node, but keeping this node's parser entry. """ if node.children and len(node.result) == 1: node._errors.extend(node.result[0].errors) node.result = node.result[0].result @transformation_factory def replace_parser(node, name: str): """Replaces the parser of a Node with a mock parser with the given name. Parameters: name(str): "NAME:PTYPE" of the surogate. The ptype is optional node(Node): The node where the parser shall be replaced """ name, ptype = (name.split(':') + [''])[:2] node.parser = MockParser(name, ptype) def flatten(node): """Recursively flattens all unnamed sub-nodes, in case there is more than one sub-node present. Flattening means that wherever a node has child nodes, the child nodes are inserted in place of the node. In other words, all leaves of this node and its child nodes are collected in-order as direct children of this node. This is meant to achieve these kinds of structural transformation: (1 (+ 2) (+ 3) -> (1 + 2 + 3) (1 (+ (2 + (3)))) -> (1 + 2 + 3) Warning: Use with care. Du tue its recursive nature, flattening can have unexpected side-effects. """ if node.children: new_result = [] for child in node.children: if not child.parser.name and child.children: assert child.children, node.as_sexpr() flatten(child) new_result.extend(child.result) else: new_result.append(child) node.result = tuple(new_result) def collapse(node): """Collapses all sub-nodes by replacing the node's result with it's string representation. """ node.result = str(node) # ------------------------------------------------ # # destructive transformations: # - tree may be rearranged (flattened), # - order is preserved # - but (irrelevant) leaves may be dropped # - errors of dropped leaves will be lost # # ------------------------------------------------ def is_whitespace(node): """Removes whitespace and comments defined with the ``@comment``-directive.""" return node.parser.ptype == WHITESPACE_PTYPE def is_empty(node): return not node.result def is_expendable(node): return is_empty(node) or is_whitespace(node) def is_token(node, tokens: AbstractSet[str] = frozenset()) -> bool: return node.parser.ptype == TOKEN_PTYPE and (not tokens or node.result in tokens) @transformation_factory(Callable) # @singledispatch def remove_children_if(node, condition): """Removes all nodes from the result field if the function ``condition(child_node)`` evaluates to ``True``.""" if node.children: node.result = tuple(c for c in node.children if not condition(c)) remove_whitespace = remove_children_if(is_whitespace) # partial(remove_children_if, condition=is_whitespace) remove_expendables = remove_children_if(is_expendable) # partial(remove_children_if, condition=is_expendable) # remove_scanner_tokens = remove_children_if(is_scanner_token) # partial(remove_children_if, condition=is_scanner_token) @transformation_factory def remove_tokens(node, tokens: AbstractSet[str] = frozenset()): """Reomoves any among a particular set of tokens from the immediate descendants of a node. If ``tokens`` is the empty set, all tokens are removed. """ remove_children_if(node, partial(is_token, tokens=tokens)) def remove_enclosing_delimiters(node): """Removes any enclosing delimiters from a structure (e.g. quotation marks from a literal or braces from a group). """ if len(node.children) >= 3: assert not node.children[0].children and not node.children[-1].children, node.as_sexpr() node.result = node.result[1:-1] def map_content(node, func: Callable[[Node], ResultType]): """Replaces the content of the node. ``func`` takes the node as an argument an returns the mapped result. """ node.result = func(node.result) ######################################################################## # # AST semantic validation functions # EXPERIMENTAL! # ######################################################################## @transformation_factory def require(node, child_tags: AbstractSet[str]): for child in node.children: if child.tag_name not in child_tags: node.add_error('Element "%s" is not allowed inside "%s".' % (child.parser.name, node.parser.name)) @transformation_factory def forbid(node, child_tags: AbstractSet[str]): for child in node.children: if child.tag_name in child_tags: node.add_error('Element "%s" cannot be nested inside "%s".' % (child.parser.name, node.parser.name)) @transformation_factory def assert_content(node, regex: str): content = str(node) if not re.match(regex, content): node.add_error('Element "%s" violates %s on %s' % (node.parser.name, str(regex), content))