syntaxtree.py 30.7 KB
Newer Older
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
"""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.
"""

20
import copy
21
import inspect
22
import os
23
from functools import partial, singledispatch
24 25 26 27
try:
    import regex as re
except ImportError:
    import re
28 29 30 31 32 33
try:
    from typing import AbstractSet, Any, ByteString, Callable, cast, Container, Dict, \
        Iterator, List, NamedTuple, Sequence, Union, Text, Tuple
except ImportError:
    from .typing34 import AbstractSet, Any, ByteString, Callable, cast, Container, Dict, \
        Iterator, List, NamedTuple, Sequence, Union, Text, Tuple
34

35
from DHParser.toolkit import log_dir, repr_call, expand_table, line_col, smart_list
36

Eckhart Arnold's avatar
Eckhart Arnold committed
37

38 39
__all__ = ['WHITESPACE_PTYPE',
           'TOKEN_PTYPE',
Eckhart Arnold's avatar
Eckhart Arnold committed
40
           'ZOMBIE_PARSER',
Eckhart Arnold's avatar
Eckhart Arnold committed
41
           'ParserBase',
Eckhart Arnold's avatar
Eckhart Arnold committed
42 43
           'Error',
           'Node',
44
           'TransformationFunc',
Eckhart Arnold's avatar
Eckhart Arnold committed
45
           'transformation_factory',
46 47
           'key_parser_name',
           'key_tag_name',
48
           'traverse',
Eckhart Arnold's avatar
Eckhart Arnold committed
49 50
           'replace_by_single_child',
           'reduce_single_child',
51
           'reduce_children',
52
           'replace_parser',
53 54
           'collapse',
           'map_content',
Eckhart Arnold's avatar
Eckhart Arnold committed
55 56 57 58
           'is_whitespace',
           'is_empty',
           'is_expendable',
           'is_token',
59 60
           'has_name',
           'has_content',
Eckhart Arnold's avatar
Eckhart Arnold committed
61
           'remove_children_if',
62 63 64 65
           'remove_children',
           'remove_content',
           'remove_first',
           'remove_last',
Eckhart Arnold's avatar
Eckhart Arnold committed
66
           'remove_whitespace',
Eckhart Arnold's avatar
Eckhart Arnold committed
67
           'remove_empty',
Eckhart Arnold's avatar
Eckhart Arnold committed
68 69 70
           'remove_expendables',
           'remove_tokens',
           'flatten',
71 72 73
           'forbid',
           'require',
           'assert_content']
Eckhart Arnold's avatar
Eckhart Arnold committed
74 75


Eckhart Arnold's avatar
Eckhart Arnold committed
76 77 78 79 80 81 82 83 84 85 86
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):
87
        return self.name or self.ptype
Eckhart Arnold's avatar
Eckhart Arnold committed
88 89 90 91 92

    @property
    def ptype(self) -> str:
        return self._ptype

93 94 95
    @property
    def repr(self) -> str:
        return self.name if self.name else repr(self)
Eckhart Arnold's avatar
Eckhart Arnold committed
96 97

class MockParser(ParserBase):
98 99
    """
    MockParser objects can be used to reconstruct syntax trees from a
Eckhart Arnold's avatar
Eckhart Arnold committed
100 101
    serialized form like S-expressions or XML. Mock objects can mimic
    different parser types by assigning them a ptype on initialization.
102 103 104 105 106
    
    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.
    """
Eckhart Arnold's avatar
Eckhart Arnold committed
107
    def __init__(self, name='', ptype=''):  # , pbases=frozenset()):
108
        assert not ptype or ptype[0] == ':'
Eckhart Arnold's avatar
Eckhart Arnold committed
109
        super(MockParser, self).__init__(name)
110
        self.name = name
Eckhart Arnold's avatar
Eckhart Arnold committed
111
        self._ptype = ptype or ':' + self.__class__.__name__
112 113 114


class ZombieParser(MockParser):
115 116 117 118 119 120 121 122 123 124 125 126
    """
    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):
127
        super(ZombieParser, self).__init__("__ZOMBIE__")
128 129 130 131
        assert not self.__class__.alive, "There can be only one!"
        assert self.__class__ == ZombieParser, "No derivatives, please!"
        self.__class__.alive = True

Eckhart Arnold's avatar
Eckhart Arnold committed
132 133 134 135 136 137
    def __copy__(self):
        return self

    def __deepcopy__(self, memo):
        return self

138 139 140 141
    def __call__(self, text):
        """Better call Saul ;-)"""
        return None, text

142 143 144 145

ZOMBIE_PARSER = ZombieParser()


146 147 148 149 150
# # Python 3.6:
# class Error(NamedTuple):
#     pos: int
#     msg: str
Error = NamedTuple('Error', [('pos', int), ('msg', str)])
151

Eckhart Arnold's avatar
Eckhart Arnold committed
152 153
StrictResultType = Union[Tuple['Node', ...], str]
ResultType = Union[Tuple['Node', ...], 'Node', str, None]
154 155


156 157 158 159 160 161 162 163 164 165 166 167
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!
168 169 170 171 172 173
        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, ...)``.
174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195
        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.
    """
196

Eckhart Arnold's avatar
Eckhart Arnold committed
197
    def __init__(self, parser, result: ResultType) -> None:
198 199 200
        """Initializes the ``Node``-object with the ``Parser``-Instance
        that generated the node and the parser's result.
        """
Eckhart Arnold's avatar
Eckhart Arnold committed
201
        self._result = ''  # type: StrictResultType
202
        self._errors = []  # type: List[str]
203
        self._children = ()  # type: Tuple['Node', ...]
204
        self.result = result
205 206 207 208
        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
209
        self.parser = parser or ZOMBIE_PARSER
210 211
        self.error_flag = any(r.error_flag for r in self.children) \
            if self.children else False  # type: bool
212 213 214

    def __str__(self):
        if self.children:
215
            return "".join(str(child) for child in self.children)
216 217 218 219 220 221 222 223
        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)
224

225
    def __eq__(self, other):
226 227
        # return str(self.parser) == str(other.parser) and self.result == other.result
        return self.tag_name == other.tag_name and self.result == other.result
228

229
    def __hash__(self):
230
        return hash(self.tag_name)
231 232 233 234 235 236 237

    def __deepcopy__(self, memodict={}):
        result = copy.deepcopy(self.result)
        other = Node(self.parser, result)
        other._pos = self._pos
        return other

238
    @property   # this needs to be a (dynamic) property, in case sef.parser gets updated
239
    def tag_name(self) -> str:
240
        return self.parser.name or self.parser.ptype
241 242

    @property
Eckhart Arnold's avatar
Eckhart Arnold committed
243
    def result(self) -> StrictResultType:
244 245 246
        return self._result

    @result.setter
Eckhart Arnold's avatar
Eckhart Arnold committed
247
    def result(self, result: ResultType):
248 249 250 251
        # # 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)
252
        self._result = (result,) if isinstance(result, Node) else result or ''
253 254
        self._children = cast(Tuple['Node', ...], self._result) \
            if isinstance(self._result, tuple) else cast(Tuple['Node', ...], ())
255 256

    @property
257
    def children(self) -> Tuple['Node', ...]:
258 259 260
        return self._children

    @property
261
    def len(self) -> int:
262
        # DEBUGGING:  print(self.tag_name, str(self.pos), str(self._len), str(self)[:10].replace('\n','.'))
263 264 265
        return self._len

    @property
266
    def pos(self) -> int:
267 268 269 270
        assert self._pos >= 0, "position value not initialized!"
        return self._pos

    @pos.setter
271 272
    def pos(self, pos: int):
        # assert isinstance(pos, int)
273 274 275 276 277 278 279
        self._pos = pos
        offset = 0
        for child in self.children:
            child.pos = pos + offset
            offset += child.len

    @property
280
    def errors(self) -> List[Error]:
281 282
        return [Error(self.pos, err) for err in self._errors]

283 284
    def show(self) -> str:
        """Returns content as string, inserting error messages where
285
        errors occurred.
286
        """
287
        s = "".join(child.show() for child in self.children) if self.children \
288 289 290
            else str(self.result)
        return (' <<< Error on "%s" | %s >>> ' % (s, '; '.join(self._errors))) if self._errors else s

291
    def _tree_repr(self, tab, openF, closeF, dataF=lambda s: s) -> str:
292 293 294 295 296 297 298 299
        """
        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.

300
        Args:
301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323
            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 = []
324
            for child in self.children:
325 326 327 328
                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

329 330
        res = cast(str, self.result)  # safe, because if there are no children, result is a string
        if head[0] == "<" and res.find('\n') < 0:
331 332 333
            # for XML: place tags for leaf-nodes on one line if possible
            return head[:-1] + self.result + tail[1:]
        else:
334
            return head + '\n'.join([tab + dataF(s) for s in res.split('\n')]) + tail
335

336
    def as_sexpr(self, src: str=None) -> str:
337 338 339
        """
        Returns content as S-expression, i.e. in lisp-like form.

340
        Args:
341 342 343 344 345
            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.
        """

346
        def opening(node) -> str:
347 348 349
            s = '(' + node.tag_name
            # s += " '(pos %i)" % node.pos
            if src:
Eckhart Arnold's avatar
Eckhart Arnold committed
350
                s += " '(pos %i " % node.pos + " %i %i)" % line_col(src, node.pos)
351 352 353 354 355 356 357 358 359 360
            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'\"')

361
        return self._tree_repr('    ', opening, lambda node: ')', pretty)
362

363
    def as_xml(self, src: str=None) -> str:
364 365 366
        """
        Returns content as XML-tree.

367
        Args:
368 369 370 371 372
            src:  The source text or `None`. In case the source text is
                given the position will also be reported as line and
                column.
        """

373
        def opening(node) -> str:
374 375 376 377 378 379 380 381 382 383 384 385 386 387 388
            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 = '</' + node.tag_name + '>'
            return s

        return self._tree_repr('    ', opening, closing)

389
    def add_error(self, error_str) -> 'Node':
390 391 392 393
        self._errors.append(error_str)
        self.error_flag = True
        return self

394 395
    def propagate_error_flags(self) -> None:
        """Recursively propagates error flags set on child nodes to its
396 397 398 399 400
        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()
401
            self.error_flag = self.error_flag or child.error_flag
402

403
    def collect_errors(self, clear_errors=False) -> List[Error]:
404 405 406 407 408
        """
        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.
        """
409 410 411 412 413
        errors = self.errors
        if clear_errors:
            self._errors = []
            self.error_flag = False
        if self.children:
414
            for child in self.children:
415
                errors.extend(child.collect_errors(clear_errors))
416
        return errors
417

Eckhart Arnold's avatar
Eckhart Arnold committed
418 419 420 421
    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())
422

423
    def find(self, match_function) -> Iterator['Node']:
424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443
        """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

444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460
    # 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
    #     """


461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482
    # 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('/'))
483 484 485 486 487 488 489 490 491


########################################################################
#
# syntax tree transformation functions
#
########################################################################


492 493 494 495
TransformationFunc = Union[Callable[[Node], Any], partial]


def transformation_factory(t=None):
Eckhart Arnold's avatar
Eckhart Arnold committed
496 497 498 499 500 501 502 503 504 505 506 507 508 509 510
    """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.
511 512 513 514 515

    Usage:
        @transformation_factory(AbtractSet[str])
        def remove_tokens(node, tokens):
            ...
Eckhart Arnold's avatar
Eckhart Arnold committed
516
      or, alternatively:
517 518 519
        @transformation_factory
        def remove_tokens(node, tokens: AbstractSet[str]):
            ...
Eckhart Arnold's avatar
Eckhart Arnold committed
520 521 522 523 524

    Example:
        trans_table = { 'expression': remove_tokens('+', '-') }
      instead of:
        trans_table = { 'expression': partial(remove_tokens, tokens={'+', '-'}) }
525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555
    """

    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)):
Eckhart Arnold's avatar
Eckhart Arnold committed
556 557 558 559
        # 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
560 561 562
        return decorator(func)
    else:
        return decorator
563 564


565 566
WHITESPACE_PTYPE = ':Whitespace'
TOKEN_PTYPE = ':Token'
567 568


569
def key_parser_name(node) -> str:
570 571 572
    return node.parser.name


573
def key_tag_name(node) -> str:
574 575 576
    return node.tag_name


577
def traverse(root_node, processing_table, key_func=key_tag_name) -> None:
578
    """Traverses the snytax tree starting with the given ``node`` depth
579
    first and applies the sequences of callback-functions registered
580 581
    in the ``calltable``-dictionary.
    
582 583
    The most important use case is the transformation of a concrete
    syntax tree into an abstract tree (AST). But it is also imaginable
584
    to employ tree-traversal for the semantic analysis of the AST.
585 586 587 588 589 590 591 592 593 594

    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)

595
    Args:
di68kap's avatar
di68kap committed
596
        root_node (Node): The root-node of the syntax tree to be traversed 
597
        processing_table (dict): node key -> sequence of functions that
di68kap's avatar
di68kap committed
598 599
            will be applied to matching nodes in order. This dictionary
            is interpreted as a ``compact_table``. See 
600
            ``toolkit.expand_table`` or ``EBNFCompiler.EBNFTransTable``
601 602
        key_func (function): A mapping key_func(node) -> keystr. The default
            key_func yields node.parser.name.
603 604 605 606 607
            
    Example:
        table = { "term": [replace_by_single_child, flatten], 
            "factor, flowmarker, retrieveop": replace_by_single_child }
        traverse(node, table)
608
    """
609 610 611 612
    # commented, because this approach is too error prone!
    # def funclist(call):
    #     return [as_partial(func) for func in smart_list(call)]

di68kap's avatar
di68kap committed
613
    # normalize processing_table entries by turning single values into lists
614
    # with a single value
615
    table = {name: smart_list(call) for name, call in list(processing_table.items())}
616
    table = expand_table(table)
617
    cache = {}  # type: Dict[str, List[Callable]]
618

di68kap's avatar
di68kap committed
619 620 621
    def traverse_recursive(node):
        if node.children:
            for child in node.result:
622
                traverse_recursive(child)            # depth first
623
                node.error_flag |= child.error_flag  # propagate error flag
624 625 626 627 628 629 630 631 632 633 634 635 636

        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

637
        for call in sequence:
di68kap's avatar
di68kap committed
638
            call(node)
639

di68kap's avatar
di68kap committed
640
    traverse_recursive(root_node)
641 642 643 644 645


# ------------------------------------------------
#
# rearranging transformations:
di68kap's avatar
di68kap committed
646 647
#     - tree may be rearranged (e.g.flattened)
#     - nodes that are not leaves may be dropped
648 649 650 651 652 653
#     - order is preserved
#     - all leaves are kept
#
# ------------------------------------------------


654 655 656 657 658 659 660 661 662 663 664 665 666
@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)


667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688
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


689 690 691 692 693 694
@transformation_factory(Callable)
def reduce_children(node, condition=lambda node: not node.name):
    """Replaces those children of node that have children themselves
    ans fulfil the given condition (default unnamed nodes).
    In contrast to ``flatten`` (see below) this transformation does not
    operate recursively.
di68kap's avatar
di68kap committed
695
    """
696 697 698 699 700 701 702 703
    if node.children:
        new_result = []
        for child in node.children:
            if child.children and condition(child):
                new_result.extend(child.children)
            else:
                new_result.append(child)
        node.result = tuple(new_result)
di68kap's avatar
di68kap committed
704 705


706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723
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:
                flatten(child)
724
                new_result.extend(child.children)
725 726 727 728 729 730 731 732 733 734 735 736
            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)


737 738 739 740 741 742 743 744 745 746 747 748 749 750
# ------------------------------------------------
#
# 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."""
751
    return node.parser.ptype == WHITESPACE_PTYPE
752 753 754 755 756

def is_empty(node):
    return not node.result

def is_expendable(node):
757
    return is_empty(node) or is_whitespace(node)
758

759
def is_token(node, tokens: AbstractSet[str] = frozenset()) -> bool:
760
    return node.parser.ptype == TOKEN_PTYPE and (not tokens or node.result in tokens)
761 762


763
@transformation_factory
764
def has_name(node, tag_names: AbstractSet[str]) -> bool:
765 766
    """Checks if node has any of a given set of `tag names`.
    See property `Node.tagname`."""
767 768 769
    return node.tag_name in tag_names


770
@transformation_factory
771
def has_content(node, contents: AbstractSet[str]) -> bool:
772 773
    """Checks if the node's content (i.e. `str(node)`) matches any of
    a given set of strings."""
774 775 776
    return str(node) in contents


777
@transformation_factory(Callable)  # @singledispatch
778
def remove_children_if(node, condition):
779 780 781 782 783 784
    """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))


785
remove_whitespace = remove_children_if(is_whitespace)  # partial(remove_children_if, condition=is_whitespace)
Eckhart Arnold's avatar
Eckhart Arnold committed
786
remove_empty = remove_children_if(is_empty)
787
remove_expendables = remove_children_if(is_expendable)  # partial(remove_children_if, condition=is_expendable)
788 789


790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807
@transformation_factory(Callable)
def remove_first(node, condition=lambda node: True):
    """Removes the first child if the condition is met.
    Otherwise does nothing."""
    if node.children:
        if condition(node.children[0]):
            node.result = node.result[1:]


@transformation_factory(Callable)
def remove_last(node, condition=lambda node: True):
    """Removes the last child if the condition is met.
    Otherwise does nothing."""
    if node.children:
        if condition(node.children[-1]):
            node.result = node.result[:-1]


808 809
@transformation_factory
def remove_tokens(node, tokens: AbstractSet[str] = frozenset()):
810 811
    """Reomoves any among a particular set of tokens from the immediate
    descendants of a node. If ``tokens`` is the empty set, all tokens
812
    are removed."""
813
    remove_children_if(node, partial(is_token, tokens=tokens))
814 815


816
@transformation_factory
817
def remove_children(node, tag_names: AbstractSet[str]):
818 819 820 821 822 823 824 825
    """Removes children by 'tag name'."""
    remove_children_if(node, partial(has_name, tag_names=tag_names))


@transformation_factory
def remove_content(node, contents: AbstractSet[str]):
    """Removes children depending on their string value."""
    remove_children_if(node, partial(has_content, contents=contents))
826 827


Eckhart Arnold's avatar
Eckhart Arnold committed
828 829
@transformation_factory
def map_content(node, func: Callable):      # Callable[[Node], ResultType]
830 831 832 833 834 835
    """Replaces the content of the node. ``func`` takes the node
    as an argument an returns the mapped result.
    """
    node.result = func(node.result)


836 837
########################################################################
#
838
# AST semantic validation functions
di68kap's avatar
di68kap committed
839
# EXPERIMENTAL!
840 841 842 843
#
########################################################################


844 845
@transformation_factory
def require(node, child_tags: AbstractSet[str]):
846
    for child in node.children:
847
        if child.tag_name not in child_tags:
848
            node.add_error('Element "%s" is not allowed inside "%s".' %
849
                           (child.parser.name, node.parser.name))
850 851


852 853
@transformation_factory
def forbid(node, child_tags: AbstractSet[str]):
854
    for child in node.children:
855
        if child.tag_name in child_tags:
856
            node.add_error('Element "%s" cannot be nested inside "%s".' %
857
                           (child.parser.name, node.parser.name))
858 859


860 861
@transformation_factory
def assert_content(node, regex: str):
862 863 864
    content = str(node)
    if not re.match(regex, content):
        node.add_error('Element "%s" violates %s on %s' %
865
                       (node.parser.name, str(regex), content))
866