# syntaxtree.py - syntax tree classes 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. """ Module ``syntaxtree`` defines the ``Node``-class for syntax trees as well as an abstract base class for parser-objects. The latter is defined here, because node-objects refer to parser-objects. All concrete parser classes are defined in the ``parse`` module. """ import collections.abc import copy from DHParser.error import Error, linebreaks, line_col from DHParser.stringview import StringView from DHParser.toolkit import re, typing from typing import Callable, cast, Iterator, List, Union, Tuple, Optional __all__ = ('ParserBase', 'WHITESPACE_PTYPE', 'TOKEN_PTYPE', 'MockParser', 'ZombieParser', 'ZOMBIE_PARSER', 'Node', 'mock_syntax_tree', 'flatten_sxpr') ####################################################################### # # parser base and mock parsers # ####################################################################### 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 __repr__(self): return self.name + self.ptype def __str__(self): return self.name + (' = ' if self.name else '') + repr(self) def __call__(self, text: StringView) -> Tuple[Optional['Node'], StringView]: return None, text @property def name(self): """Returns the name of the parser or the empty string '' for unnamed parsers.""" return self._name @property def ptype(self) -> str: """Returns the type of the parser. By default this is the parser's class name preceded by a colon, e.g. ':ZeroOrMore'.""" return self._ptype @property def repr(self) -> str: """Returns the parser's name if it has a name and repr()""" return self.name if self.name else repr(self) def reset(self): """Resets any parser variables. (Should be overridden.)""" pass def grammar(self) -> Optional[object]: """Returns the Grammar object to which the parser belongs. If not yet connected to any Grammar object, None is returned.""" return None def apply(self, func: Callable) -> bool: """Applies the function `func` to the parser. Returns False, if - for whatever reason - the functions has not been applied, True otherwise.""" return False WHITESPACE_PTYPE = ':Whitespace' TOKEN_PTYPE = ':Token' 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().__init__(name) self._ptype = ptype or ':' + self.__class__.__name__ 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() ####################################################################### # # syntaxtree nodes # ####################################################################### ChildrenType = Tuple['Node', ...] NoChildren = cast(ChildrenType, ()) # type: ChildrenType StrictResultType = Union[ChildrenType, StringView, str] ResultType = Union[ChildrenType, 'Node', StringView, str, None] def flatten_sxpr(sxpr: str) -> str: """Returns S-expression ``sxpr`` as a one-liner without unnecessary whitespace. Example: >>> flatten_sxpr('(a\\n (b\\n c\\n )\\n)\\n') '(a (b c))' """ return re.sub(r'\s(?=\))', '', re.sub(r'\s+', ' ', sxpr)).strip() class Node(collections.abc.Sized): """ 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! content (str): Yields the contents of the tree as string. The difference to ``str(node)`` is that ``node.content`` does not add the error messages to the returned string. 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 error_flag (int): 0 if no error occurred in either the node itself or any of its descendants. Otherwise contains the highest warning or error level or all errors that occurred. 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 and 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 during the parsing stage and never during or after the AST-transformation. xml_attr (dict): An optional dictionary of XML-attributes. This dictionary is created lazily upon first usage. The attributes will only be shown in the XML-Representation, not in the S-Expression-output. _parent (Node): SLOT RESERVED FOR FUTURE USE! """ __slots__ = ['_result', 'children', '_errors', '_len', '_pos', 'parser', 'error_flag', '_xml_attr', '_parent'] def __init__(self, parser, result: ResultType, leafhint: bool = False) -> None: """ Initializes the ``Node``-object with the ``Parser``-Instance that generated the node and the parser's result. """ self.error_flag = 0 # type: int self._errors = [] # type: List[Error] self._pos = -1 # type: int # Assignment to self.result initializes the attributes _result, children and _len # The following if-clause is merely an optimization, i.e. a fast-path for leaf-Nodes if leafhint: self._result = result # type: StrictResultType self.children = NoChildren # type: ChildrenType self._len = -1 # type: int # lazy evaluation else: self.result = result self.parser = parser or ZOMBIE_PARSER def __str__(self): s = "".join(str(child) for child in self.children) if self.children else self.result if self._errors: return ' <<< Error on "%s" | %s >>> ' % \ (s, '; '.join(e.message for e in self._errors)) return s 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 __len__(self): if self._len < 0: self._len = sum(len(child) for child in self.children) \ if self.children else len(self._result) return self._len def __bool__(self): # A node that is not None is always True, even if it's empty return True def __eq__(self, other): """ Equality of nodes: Two nodes are considered as equal, if their tag name is the same and if their results are equal. """ 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 def __getitem__(self, index_or_tagname: Union[int, str]) -> Union['Node', Iterator['Node']]: """ Returns the child node with the given index if ``index_or_tagname`` is an integer value or a generator that yields all descendant nodes that match a particular tag name. Examples:: >>> tree = mock_syntax_tree('(a (b "X") (X (c "d")) (e (X "F")))') >>> flatten_sxpr(tree[0].as_sxpr()) '(b "X")' >>> list(flatten_sxpr(item.as_sxpr()) for item in tree["X"]) ['(X (c "d"))', '(X "F")'] Args: index_or_tagname(str): Either an index of a child node or a tag name. Return: Node: All nodes which have a given tag name. """ if isinstance(index_or_tagname, int): children = self.children if children: return children[index_or_tagname] else: raise ValueError('Leave nodes have no children that can be indexed!') else: match_function = lambda node: node.tag_name == index_or_tagname return self.find(match_function, False) def __contains__(self, tag_name: str) -> bool: """ Returns true if a descendant with the given tag name exists. Args: tag_name: tag_name which will be searched among the descendant nodes Returns: bool: True, if at least one descendant node with the given tag name exists, False otherwise """ generator = self[tag_name] try: generator.__next__() return True except StopIteration: return False @property # this needs to be a (dynamic) property, in case sef.parser gets updated def tag_name(self) -> str: """ Returns the tage name of Node, i.e. the name for XML or S-expression representation. By default the tag name is the name of the node's parser or, if the node's parser is unnamed, the node's parser's `ptype`. """ return self.parser.name or self.parser.ptype @property def result(self) -> StrictResultType: """ Returns the result from the parser that created the node. Error messages are not included in the result. Use `self.content()` if the result plus any error messages is needed. """ return self._result @result.setter def result(self, result: ResultType): # # made obsolete by static type checking with mypy # assert ((isinstance(result, tuple) and all(isinstance(child, Node) for child in result)) # or isinstance(result, Node) # or isinstance(result, str)), str(result) # Possible optimization: Do not allow single nodes as argument: # assert not isinstance(result, Node) self._len = -1 # lazy evaluation if isinstance(result, Node): self.children = (result,) self._result = self.children self.error_flag = result.error_flag # if self._pos < 0: # self._pos = result._pos else: if isinstance(result, tuple): self.children = result self._result = result or '' if result: if self.error_flag == 0: self.error_flag = max(child.error_flag for child in self.children) # if self._pos < 0: # self._pos = result[0]._pos else: self.children = NoChildren self._result = str(result) # # shorter but slower: # self._result = (result,) if isinstance(result, Node) else result or '' # type: StrictResultType # self.children = cast(ChildrenType, self._result) \ # if isinstance(self._result, tuple) else NoChildren # type: ChildrenType # if self.children: # self.error_flag = max(self.error_flag, # max(child.error_flag for child in self.children)) # type: bool @property def content(self) -> str: """ Returns content as string, omitting error messages. """ if self.children: return "".join(child.content for child in self.children) return cast(str, self._result) @property def structure(self) -> str: """ Return structure (and content) as S-expression on a single line without any line breaks. """ return flatten_sxpr(self.as_sxpr(showerrors=False)) @property def pos(self) -> int: """Returns the position of the Node's content in the source text.""" if self._pos < 0: raise AssertionError("Position value not initialized!") return self._pos def init_pos(self, pos: int, overwrite: bool = False) -> 'Node': """ (Re-)initialize position value. Usually, the parser guard (`parsers.add_parser_guard()`) takes care of assigning the position in the document to newly created nodes. However, where Nodes are created outside the reach of the parser guard, their document-position must be assigned manually. This function recursively reassigns the position values of the child nodes, too. """ if overwrite or self._pos < 0: self._pos = pos for err in self._errors: err.pos = pos else: assert self._pos == pos, str("%i != %i" % (self._pos, pos)) # recursively adjust pos-values of all children offset = self.pos for child in self.children: child.init_pos(offset, overwrite) offset = child.pos + len(child) return self @property def errors(self) -> List[Error]: """ Returns the errors that occurred at this Node, not including any errors from child nodes. """ return self._errors.copy() def add_error(self, message: str, code: int = Error.ERROR) -> 'Node': """ Adds an error to this Node. Parameters: message(str): A string with the error message.abs code(int): An error code to identify the kind of error """ self._errors.append(Error(message, code)) self.error_flag = max(self.error_flag, self._errors[-1].code) return self def collect_errors(self, clear_errors=False) -> List[Error]: """ Recursively adds line- and column-numbers to all error objects. 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 for err in errors: err.pos = self.pos if self.children: for child in self.children: errors.extend(child.collect_errors(clear_errors)) if clear_errors: self._errors = [] self.error_flag = 0 else: if self._errors: self.error_flag = max(err.code for err in self.errors) if self.children: max_child_error = max(child.error_flag for child in self.children) self.error_flag = max(self.error_flag, max_child_error) return errors def _tree_repr(self, tab, open_fn, close_fn, data_fn=lambda i: i, density=0) -> 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 ' ' open_fn: (Node->str) A function that returns an opening string (e.g. an XML-tag_name) for a given node close_fn: (Node->str) A function that returns a closeF string (e.g. an XML-tag_name) for a given node. data_fn: (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 = open_fn(self) tail = close_fn(self) if not self.result: return head.rstrip() + tail.lstrip() tail = tail.lstrip(None if density & 2 else '') if self.children: content = [] for child in self.children: subtree = child._tree_repr(tab, open_fn, close_fn, data_fn, density).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 density & 1 and res.find('\n') < 0: # and head[0] == "<": # except for XML, add a gap between opening statement and content gap = ' ' if head.rstrip()[-1] != '>' else '' return head.rstrip() + gap + data_fn(self.result) + tail.lstrip() else: return head + '\n'.join([tab + data_fn(s) for s in res.split('\n')]) + tail def as_sxpr(self, src: str = None, compact: bool = False, showerrors: bool = True) -> 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. compact: If True a compact representation is returned where brackets are omitted and only the indentation indicates the tree structure. """ left_bracket, right_bracket, density = ('', '', 1) if compact else ('(', '\n)', 0) def opening(node) -> str: """Returns the opening string for the representation of `node`.""" txt = left_bracket + node.tag_name # s += " '(pos %i)" % node.pos if src: txt += " '(pos %i " % node.pos # + " %i %i)" % line_col(src, node.pos) # if node.error_flag: # just for debugging error collecting # txt += " HAS ERRORS" if showerrors and node.errors: txt += " '(err '(%s))" % ' '.join(str(err).replace('"', r'\"') for err in node.errors) return txt + '\n' def closing(node) -> str: """Returns the closing string for the representation of `node`.""" return right_bracket def pretty(strg): """Encloses `strg` with the right kind of quotation marks.""" return '"%s"' % strg if strg.find('"') < 0 \ else "'%s'" % strg if strg.find("'") < 0 \ else '"%s"' % strg.replace('"', r'\"') return self._tree_repr(' ', opening, closing, pretty, density=density) @property def xml_attr(self): """Returns a dictionary of XML-Attributes attached to the Node.""" if not hasattr(self, '_xml_attr'): self._xml_attr = dict() return self._xml_attr def as_xml(self, src: str = None, showerrors: bool = True) -> 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: """Returns the opening string for the representation of `node`.""" txt = ['<', node.tag_name] # s += ' pos="%i"' % node.pos if hasattr(node, '_xml_attr'): txt.extend(' %s="%s"' % (k, v) for k, v in node.xml_attr.items()) if src: txt.append(' line="%i" col="%i"' % line_col(line_breaks, node.pos)) if showerrors and node.errors: txt.append(' err="%s"' % ''.join(str(err).replace('"', r'\"') for err in node.errors)) return "".join(txt + [">\n"]) def closing(node): """Returns the closing string for the representation of `node`.""" return '\n' line_breaks = linebreaks(src) if src else [] return self._tree_repr(' ', opening, closing, density=1) def find(self, match_function: Callable, include_root: bool=True) -> Iterator['Node']: """ Finds nodes in the tree that fulfill a given 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 include_root (bool): If False, only descendant nodes will be checked for a match. Yields: Node: All nodes of the tree for which ``match_function(node)`` returns True """ if include_root and match_function(self): yield self else: for child in self.children: for node in child.find(match_function, True): yield node def find_by_tag(self, tag_name: str) -> Iterator['Node']: """ Finds all nodes with the given tag name. Args: tag_name(str): The tag name that is being searched for. Yields: Node: All nodes which have a given tag name. """ def tree_size(self) -> int: """ Recursively counts the number of nodes in the tree including the root node. """ return sum(child.tree_size() for child in self.children) + 1 def mock_syntax_tree(sxpr): """ Generates a tree of nodes from an S-expression. The main purpose of this is to generate test data. Example: >>> mock_syntax_tree("(a (b c))").as_sxpr() '(a\\n (b\\n "c"\\n )\\n)' """ def next_block(s): """Generator that yields all characters until the next closing bracket that does not match an opening bracket matched earlier within the same package.""" s = s.strip() try: while s[0] != ')': if s[0] != '(': raise ValueError('"(" expected, not ' + s[:10]) # assert s[0] == '(', s level = 1 k = 1 while level > 0: if s[k] == '(': level += 1 elif s[k] == ')': level -= 1 k += 1 yield s[:k] s = s[k:].strip() except IndexError: errmsg = ('Malformed S-expression. Unprocessed part: "%s"' % s) if s \ else 'Malformed S-expression. Closing bracket(s) ")" missing.' raise AssertionError(errmsg) sxpr = sxpr.strip() if sxpr[0] != '(': raise ValueError('"(" expected, not ' + sxpr[:10]) # assert sxpr[0] == '(', sxpr sxpr = sxpr[1:].strip() match = re.match(r'[\w:]+', sxpr) if match is None: raise AssertionError('Malformed S-expression Node-tagname or identifier expected, ' 'not "%s"' % sxpr[:40].replace('\n', '')) name, class_name = (sxpr[:match.end()].split(':') + [''])[:2] sxpr = sxpr[match.end():].strip() if sxpr[0] == '(': result = tuple(mock_syntax_tree(block) for block in next_block(sxpr)) pos = 0 for node in result: node._pos = pos pos += len(node) else: lines = [] while sxpr and sxpr[0] != ')': for qtmark in ['"""', "'''", '"', "'"]: match = re.match(qtmark + r'.*?' + qtmark, sxpr, re.DOTALL) if match: i = len(qtmark) lines.append(sxpr[i:match.end() - i]) sxpr = sxpr[match.end():].strip() break else: match = re.match(r'(?:(?!\)).)*', sxpr, re.DOTALL) lines.append(sxpr[:match.end()]) sxpr = sxpr[match.end():] result = "\n".join(lines) node = Node(MockParser(name, ':' + class_name), result) node._pos = 0 return node # if __name__ == "__main__": # st = mock_syntax_tree("(alpha (beta (gamma i\nj\nk) (delta y)) (epsilon z))") # print(st.as_sxpr()) # print(st.as_xml())