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syntaxtree.py 24.4 KB
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"""syntaxtree.py - syntax tree classes for DHParser
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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.
"""

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import collections.abc
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import copy
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from functools import partial

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from DHParser.error import Error, linebreaks, line_col
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from DHParser.stringview import StringView
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from DHParser.toolkit import re, typing
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from typing import Any, Callable, cast, Iterator, List, Union, Tuple, Hashable, Optional

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__all__ = ('ParserBase',
           'WHITESPACE_PTYPE',
           'TOKEN_PTYPE',
           'MockParser',
           'ZombieParser',
           'ZOMBIE_PARSER',
           'Node',
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           'mock_syntax_tree',
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           'flatten_sxpr',
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           'TransformationFunc')
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#######################################################################
#
# 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()):
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        self._name = name  # type: str
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        self._ptype = ':' + self.__class__.__name__  # type: str

    def __repr__(self):
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         return self.name + self.ptype
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    def __str__(self):
        return self.name + (' = ' if self.name else '') + repr(self)

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    def __call__(self, text: StringView) -> Tuple[Optional['Node'], StringView]:
        return None, text

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    @property
    def name(self):
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        """Returns the name of the parser or the empty string '' for unnamed
        parsers."""
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        return self._name

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    @property
    def ptype(self) -> str:
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        """Returns the type of the parser. By default this is the parser's
        class name preceded by a colon, e.g. ':ZeroOrMore'."""
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        return self._ptype

    @property
    def repr(self) -> str:
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        """Returns the parser's name if it has a name and repr()"""
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        return self.name if self.name else repr(self)

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    def reset(self):
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        """Resets any parser variables. (Should be overridden.)"""
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        pass

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    def grammar(self) -> Optional[object]:
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        """Returns the Grammar object to which the parser belongs. If not
        yet connected to any Grammar object, None is returned."""
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        return None

    def apply(self, func: Callable) -> bool:
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        """Applies the function `func` to the parser. Returns False, if
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        - for whatever reason - the functions has not been applied, True
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        otherwise."""
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        return False

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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] == ':'
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        super().__init__(name)
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        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
#
#######################################################################


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ChildrenType = Tuple['Node', ...]
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NoChildren = cast(ChildrenType, ())  # type: ChildrenType
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StrictResultType = Union[ChildrenType, str]
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ResultType = Union[ChildrenType, 'Node', StringView, str, None]
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def flatten_sxpr(sxpr: str) -> str:
    """Returns S-expression `sxpr` as a one-liner without unnecessary
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    whitespace.

    Example:
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    >>> flatten_sxpr('(a\\n    (b\\n        c\\n    )\\n)\\n')
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    '(a (b c))'
    """
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    return re.sub(r'\s(?=\))', '', re.sub(r'\s+', ' ', sxpr)).strip()
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class Node(collections.abc.Sized):
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    """
    Represents a node in the concrete or abstract syntax tree.

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    Attributes and Properties:
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        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!
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        parser (Parser):  The parser which generated this node.
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            WARNING: In case you use mock syntax trees for testing or
            parser replacement during the AST-transformation: DO NOT
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            rely on this being a real parser object in any phase after
            parsing (i.e. AST-transformation and compiling), for
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            example by calling ``isinstance(node.parer, ...)``.
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        errors (list):  A list of parser- or compiler-errors:
            tuple(position, string) attached to this node
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        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.
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        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
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            the length before AST-transformation and will never change
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            through AST-transformation. READ ONLY!
        pos (int):  the position of the node within the parsed text.

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            The value of ``pos`` is -1 meaning invalid by default.
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            Setting this value will set the positions of all child
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            nodes relative to this value.
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            To set the pos values of all nodes in a syntax tree, the
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            pos value of the root node should be set to 0 right
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            after parsing.

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            Other than that, this value should be considered READ ONLY.
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            At any rate, it should only be reassigned during the parsing
            stage and never during or after the AST-transformation.
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    """
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    __slots__ = ['_result', 'children', '_errors', '_len', '_pos', 'parser', 'error_flag']

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    def __init__(self, parser, result: ResultType, leafhint: bool = False) -> None:
        """
        Initializes the ``Node``-object with the ``Parser``-Instance
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        that generated the node and the parser's result.
        """
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        self.error_flag = 0             # type: int
        self._errors = []               # type: List[Error]
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        self._pos = -1                  # type: int
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        # 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
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        if leafhint:
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            self._result = str(result)  # type: StrictResultType
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            self.children = NoChildren  # type: ChildrenType
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            self._len = -1              # type: int  # lazy evaluation
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        else:
            self.result = result
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        self.parser = parser or ZOMBIE_PARSER

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    def __str__(self):
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        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
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    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)
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    def __len__(self):
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        if self._len < 0:
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            self._len = sum(len(child) for child in self.children) \
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                if self.children else len(self._result)
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        return self._len


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    def __bool__(self):
        # A node that is not None is always True, even if it's empty
        return True


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    def __eq__(self, other):
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        # return str(self.parser) == str(other.parser) and self.result == other.result
        return self.tag_name == other.tag_name and self.result == other.result
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    def __hash__(self):
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        return hash(self.tag_name)
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    def __deepcopy__(self, memodict={}):
        result = copy.deepcopy(self.result)
        other = Node(self.parser, result)
        other._pos = self._pos
        return other

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    @property   # this needs to be a (dynamic) property, in case sef.parser gets updated
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    def tag_name(self) -> str:
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        """
        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`.
        """
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        return self.parser.name or self.parser.ptype
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    @property
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    def result(self) -> StrictResultType:
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        """
        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.
        """
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        return self._result

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    @result.setter
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    def result(self, result: ResultType):
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        # # made obsolete by static type checking with mypy
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        # assert ((isinstance(result, tuple) and all(isinstance(child, Node) for child in result))
        #         or isinstance(result, Node)
        #         or isinstance(result, str)), str(result)
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        # Possible optimization: Do not allow single nodes as argument:
        # assert not isinstance(result, Node)
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        self._len = -1  # lazy evaluation
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        if isinstance(result, Node):
            self.children = (result,)
            self._result = self.children
            self.error_flag = result.error_flag
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            # if self._pos < 0:
            #     self._pos = result._pos
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        else:
            if isinstance(result, tuple):
                self.children = result
                self._result = result or ''
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                if result:
                    if self.error_flag == 0:
                        self.error_flag = max(child.error_flag for child in self.children)
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                    # if self._pos < 0:
                    #     self._pos = result[0]._pos
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            else:
                self.children = NoChildren
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                self._result = str(result)
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        # # 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

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    @property
    def content(self) -> str:
        """
        Returns content as string, inserting error messages where
        errors occurred.
        """
        if self.children:
            return "".join(child.content for child in self.children)
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        return cast(str, self._result)
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    @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))


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    @property
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    def pos(self) -> int:
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        """Returns the position of the Node's content in the source text."""
        if self._pos < 0:
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            raise AssertionError("Position value not initialized!")
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        return self._pos

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    def init_pos(self, pos: int, overwrite: bool = False) -> 'Node':
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        """
        (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.
        """
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        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))
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        # recursively adjust pos-values of all children
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        offset = self.pos
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        for child in self.children:
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            child.init_pos(offset, overwrite)
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            offset = child.pos + len(child)
        return self

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    @property
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    def errors(self) -> List[Error]:
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        """
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        Returns the errors that occurred at this Node,
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        not including any errors from child nodes.
        """
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        return self._errors.copy()

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    def add_error(self,
                  message: str,
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                  code: int = Error.ERROR) -> 'Node':
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        """
        Adds an error to this Node.
        Parameters:
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            message(str): A string with the error message.abs
            code(int):    An error code to identify the kind of error
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        """
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        self._errors.append(Error(message, code))
        self.error_flag = max(self.error_flag, self._errors[-1].code)
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        return self

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    def collect_errors(self, clear_errors=False) -> List[Error]:
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        """
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        Recursively adds line- and column-numbers to all error objects.
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        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.
        """
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        errors = self.errors
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        for err in errors:
            err.pos = self.pos
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        if self.children:
            for child in self.children:
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                errors.extend(child.collect_errors(clear_errors))
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        if clear_errors:
            self._errors = []
            self.error_flag = 0
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        else:
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            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

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    def _tree_repr(self, tab, open_fn, close_fn, data_fn=lambda i: i, density=0) -> str:
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        """
        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.

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        Args:
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            tab (str):  The indentation string, e.g. '\t' or '    '
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            open_fn:   (Node->str) A function that returns an opening
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                string (e.g. an XML-tag_name) for a given node
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            close_fn:  (Node->str) A function that returns a closeF
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                string (e.g. an XML-tag_name) for a given node.
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            data_fn:   (str->str) A function that filters the data string
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                before printing, e.g. to add quotation marks

        Returns (str):
            A string that contains a (serialized) tree representation
            of the node and its children.
        """
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        head = open_fn(self)
        tail = close_fn(self)
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        if not self.result:
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            return head.rstrip() + tail.lstrip()
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        tail = tail.lstrip(None if density & 2 else '')
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        if self.children:
            content = []
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            for child in self.children:
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                subtree = child._tree_repr(tab, open_fn, close_fn, data_fn, density).split('\n')
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                content.append('\n'.join((tab + s) for s in subtree))
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            return head + '\n'.join(content) + tail
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        res = cast(str, self.result)  # safe, because if there are no children, result is a string
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        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 ''
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            return head.rstrip() + gap + data_fn(self.result) + tail.lstrip()
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        else:
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            return head + '\n'.join([tab + data_fn(s) for s in res.split('\n')]) + tail
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    def as_sxpr(self, src: str = None, compact: bool = False, showerrors: bool = True) -> str:
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        """
        Returns content as S-expression, i.e. in lisp-like form.

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        Args:
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            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.
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            compact:  If True a compact representation is returned where
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                brackets are omitted and only the indentation indicates the
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                tree structure.
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        """

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        left_bracket, right_bracket, density = ('', '', 1) if compact else ('(', '\n)', 0)
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        def opening(node) -> str:
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            """Returns the opening string for the representation of `node`."""
            txt = left_bracket + node.tag_name
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            # s += " '(pos %i)" % node.pos
            if src:
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                txt += " '(pos %i " % node.pos  # + " %i %i)" % line_col(src, node.pos)
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            # if node.error_flag:   # just for debugging error collecting
            #     txt += " HAS ERRORS"
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            if showerrors and node.errors:
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                txt += " '(err '(%s))" % ' '.join(str(err).replace('"', r'\"')
                                                  for err in node.errors)
            return txt + '\n'
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        def closing(node) -> str:
            """Returns the closing string for the representation of `node`."""
            return right_bracket
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        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'\"')
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        return self._tree_repr('    ', opening, closing, pretty, density=density)
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    @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


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    def as_xml(self, src: str = None, showerrors: bool = True) -> str:
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        """
        Returns content as XML-tree.

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        Args:
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            src:  The source text or `None`. In case the source text is
                given the position will also be reported as line and
                column.
        """

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        def opening(node) -> str:
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            """Returns the opening string for the representation of `node`."""            
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            txt = ['<', node.tag_name]
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            # s += ' pos="%i"' % node.pos
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            if hasattr(self, '_xml_attr'):
                txt.extend(' %s="%s"' % (k, v) for k, v in self.xml_attr.items())
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            if src:
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                txt.append(' line="%i" col="%i"' % line_col(line_breaks, node.pos))
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            if showerrors and node.errors:
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                txt.append(' err="%s"' % ''.join(str(err).replace('"', r'\"')
                                                 for err in node.errors))
            return "".join(txt + [">\n"])
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        def closing(node):
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            """Returns the closing string for the representation of `node`."""            
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            return '\n</' + node.tag_name + '>'
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        line_breaks = linebreaks(src) if src else []
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        return self._tree_repr('    ', opening, closing, density=1)
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    def find(self, match_function: Callable) -> Iterator['Node']:
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        """
        Finds nodes in the tree that match a specific criterion.

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        `find` is a generator that yields all nodes for which the
        given `match_function` evaluates to True. The tree is
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        traversed pre-order.
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        Args:
            match_function (function): A function  that takes as Node
                object as argument and returns True or False
        Yields:
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            Node: all nodes of the tree for which
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            ``match_function(node)`` returns True
        """
        if match_function(self):
            yield self
        else:
            for child in self.children:
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                for node in child.find(match_function):
                    yield node
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    def tree_size(self) -> int:
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        """
        Recursively counts the number of nodes in the tree including the root node.
        """
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        return sum(child.tree_size() for child in self.children) + 1


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def mock_syntax_tree(sxpr):
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    """
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    Generates a tree of nodes from an S-expression. The main purpose of this is
    to generate test data.
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    Example:
    >>> mock_syntax_tree("(a (b c))").as_sxpr()
    '(a\\n    (b\\n        "c"\\n    )\\n)'
    """

    def next_block(s):
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        """Generator that yields all characters until the next closing bracket
        that does not match an opening bracket matched earlier within the same
        package."""
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        s = s.strip()
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        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)
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    sxpr = sxpr.strip()
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    if sxpr[0] != '(':
        raise ValueError('"(" expected, not ' + sxpr[:10])
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    # assert sxpr[0] == '(', sxpr
    sxpr = sxpr[1:].strip()
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    match = re.match(r'[\w:]+', sxpr)
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    if match is None:
        raise AssertionError('Malformed S-expression Node-tagname or identifier expected, '
                             'not "%s"' % sxpr[:40].replace('\n', ''))
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    name, class_name = (sxpr[:match.end()].split(':') + [''])[:2]
    sxpr = sxpr[match.end():].strip()
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    if sxpr[0] == '(':
        result = tuple(mock_syntax_tree(block) for block in next_block(sxpr))
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        pos = 0
        for node in result:
            node._pos = pos
            pos += len(node)
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    else:
        lines = []
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        while sxpr and sxpr[0] != ')':
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            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()
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                    break
            else:
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                match = re.match(r'(?:(?!\)).)*', sxpr, re.DOTALL)
                lines.append(sxpr[:match.end()])
                sxpr = sxpr[match.end():]
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        result = "\n".join(lines)
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    node = Node(MockParser(name, ':' + class_name), result)
    node._pos = 0
    return node
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TransformationFunc = Union[Callable[[Node], Any], partial]
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# 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())