parse.py 140 KB
Newer Older
1
# parse.py - parser combinators for DHParser
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
#
# 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.
Eckhart Arnold's avatar
Eckhart Arnold committed
17

18
19

"""
20
Module ``parse`` contains the python classes and functions for
21
22
DHParser's packrat-parser. It's central class is the
``Grammar``-class, which is the base class for any concrete
23
24
25
26
27
28
29
30
31
Grammar. Grammar-objects are callable and parsing is done by
calling a Grammar-object with a source text as argument.

The different parsing functions are callable descendants of class
``Parser``. Usually, they are organized in a tree and defined
within the namespace of a grammar-class. See ``ebnf.EBNFGrammar``
for an example.
"""

32

33
from collections import defaultdict
34
import copy
eckhart's avatar
eckhart committed
35
from typing import Callable, cast, List, Tuple, Set, Dict, \
eckhart's avatar
eckhart committed
36
    DefaultDict, Sequence, Union, Optional
37

eckhart's avatar
eckhart committed
38
from DHParser.configuration import get_config_value
39
40
from DHParser.error import Error, ErrorCode, is_error, MANDATORY_CONTINUATION, \
    LEFT_RECURSION_WARNING, UNDEFINED_RETRIEVE, PARSER_LOOKAHEAD_FAILURE_ONLY, \
eckhart's avatar
eckhart committed
41
    PARSER_LOOKAHEAD_MATCH_ONLY, PARSER_STOPPED_BEFORE_END, PARSER_NEVER_TOUCHES_DOCUMENT, \
42
43
44
    MALFORMED_ERROR_STRING, MANDATORY_CONTINUATION_AT_EOF, DUPLICATE_PARSERS_IN_ALTERNATIVE, \
    CAPTURE_WITHOUT_PARSERNAME, CAPTURE_DROPPED_CONTENT_WARNING, LOOKAHEAD_WITH_OPTIONAL_PARSER, \
    BADLY_NESTED_OPTIONAL_PARSER, BAD_ORDER_OF_ALTERNATIVES, BAD_MANDATORY_SETUP, \
45
46
    OPTIONAL_REDUNDANTLY_NESTED_WARNING, CAPTURE_STACK_NOT_EMPTY, BAD_REPETITION_COUNT, \
    AUTORETRIEVED_SYMBOL_NOT_CLEARED, RECURSION_DEPTH_LIMIT_HIT
eckhart's avatar
eckhart committed
47
from DHParser.log import CallItem, HistoryRecord
48
from DHParser.preprocess import BEGIN_TOKEN, END_TOKEN, RX_TOKEN_NAME
49
from DHParser.stringview import StringView, EMPTY_STRING_VIEW
eckhart's avatar
eckhart committed
50
from DHParser.syntaxtree import ChildrenType, Node, RootNode, WHITESPACE_PTYPE, \
51
    TOKEN_PTYPE, ZOMBIE_TAG, EMPTY_NODE, ResultType
52
from DHParser.toolkit import sane_parser_name, escape_control_characters, re, cython, \
53
    abbreviate_middle, RX_NEVER_MATCH, RxPatternType, linebreaks, line_col
54

55
__all__ = ('ParserError',
eckhart's avatar
eckhart committed
56
57
58
           'ApplyFunc',
           'FlagFunc',
           'ParseFunc',
59
           'Parser',
60
           'UnknownParserError',
61
           'AnalysisError',
62
           'GrammarError',
63
           'Grammar',
64
65
           'Always',
           'Never',
eckhart's avatar
eckhart committed
66
           'AnyChar',
67
           'PreprocessorToken',
68
69
           'Text',
           'DropText',
70
           'RegExp',
71
72
           'RE',
           'TKN',
73
           'Whitespace',
74
           'DropRegExp',
75
           'mixin_comment',
di68kap's avatar
di68kap committed
76
           'mixin_nonempty',
di68kap's avatar
di68kap committed
77
           'CombinedParser',
eckhart's avatar
eckhart committed
78
79
           'UnaryParser',
           'NaryParser',
80
           'Drop',
81
82
83
84
           'Synonym',
           'Option',
           'ZeroOrMore',
           'OneOrMore',
85
           'NO_MANDATORY',
Eckhart Arnold's avatar
Eckhart Arnold committed
86
           'MandatoryNary',
87
88
           'Series',
           'Alternative',
89
           'INFINITE',
90
           'Counted',
91
           'Interleave',
eckhart's avatar
eckhart committed
92
           'Required',
93
94
95
96
97
           'Lookahead',
           'NegativeLookahead',
           'Lookbehind',
           'NegativeLookbehind',
           'last_value',
98
99
           'optional_last_value',
           'matching_bracket',
100
101
102
           'Capture',
           'Retrieve',
           'Pop',
103
           'Forward')
104
105
106
107


########################################################################
#
108
# ParserError class
109
110
111
112
#
########################################################################


Eckhart Arnold's avatar
Eckhart Arnold committed
113
114
115
class ParserError(Exception):
    """
    A `ParserError` is thrown for those parser errors that allow the
116
    controlled re-entrance of the parsing process after the error occurred.
Eckhart Arnold's avatar
Eckhart Arnold committed
117
    If a reentry-rule has been configured for the parser where the error
118
    occurred, the parser guard can resume the parsing process.
Eckhart Arnold's avatar
Eckhart Arnold committed
119
120

    Currently, the only case when a `ParserError` is thrown (and not some
121
    different kind of error like `UnknownParserError`) is when a `Series`-
eckhart's avatar
eckhart committed
122
    or `Interleave`-parser detects a missing mandatory element.
Eckhart Arnold's avatar
Eckhart Arnold committed
123
    """
eckhart's avatar
eckhart committed
124
    def __init__(self, node: Node, rest: StringView, error: Error, first_throw: bool):
eckhart's avatar
eckhart committed
125
        assert node is not None
eckhart's avatar
eckhart committed
126
127
128
        self.node = node    # type: Node
        self.rest = rest    # type: StringView
        self.error = error  # type: Error
129
        self.first_throw = first_throw  # type: bool
eckhart's avatar
eckhart committed
130
        self.frozen_callstack = tuple()  # type: Tuple[CallItem, ...]  # tag_name, location
Eckhart Arnold's avatar
Eckhart Arnold committed
131

132
    def __str__(self):
133
        return "%i: %s    %s" % (self.node.pos, str(self.rest[:25]), repr(self.node))
134

Eckhart Arnold's avatar
Eckhart Arnold committed
135

136
137
138
ResumeList = List[Union[RxPatternType, str, Callable]]  # list of strings or regular expressiones
ReentryPointAlgorithm = Callable[[StringView, int], Tuple[int, int]]
# (text, start point) => (reentry point, match length)
139
# A return value of (-1, x) means that no reentry point before the end of the document was found
Eckhart Arnold's avatar
Eckhart Arnold committed
140
141


eckhart's avatar
eckhart committed
142
@cython.locals(upper_limit=cython.int, closest_match=cython.int, pos=cython.int)
143
144
145
def reentry_point(rest: StringView,
                  rules: ResumeList,
                  comment_regex,
146
                  search_window: int = -1) -> int:
Eckhart Arnold's avatar
Eckhart Arnold committed
147
148
    """
    Finds the point where parsing should resume after a ParserError has been caught.
149
    The algorithm makes sure that this reentry-point does not lie inside a comment.
150
151
152
    The re-entry point is always the point after the end of the match of the regular
    expression defining the re-entry point. (Use look ahead, if you wand to define
    the re-entry point by what follows rather than by what text precedes the point.)
Eckhart Arnold's avatar
Eckhart Arnold committed
153
154
    Args:
        rest:  The rest of the parsed text or, in other words, the point where
155
            a ParserError was thrown.
156
157
        rules: A list of strings, regular expressions or callable, i.e.
            reentry-point-search-functions. The rest of the text is searched for
158
159
            each of these. The closest match is the point where parsing will be
            resumed.
160
        comment_regex: A regular expression object that matches comments.
161
162
        search_window: The maximum size of the search window for finding the
            reentry-point. A value smaller or equal zero means that
Eckhart Arnold's avatar
Eckhart Arnold committed
163
    Returns:
164
165
        The integer index of the closest reentry point or -1 if no reentry-point
        was found.
Eckhart Arnold's avatar
Eckhart Arnold committed
166
    """
167
    upper_limit = len(rest) + 1
168
    closest_match = upper_limit
169
170
    comments = None  # typ: Optional[Iterator]

eckhart's avatar
eckhart committed
171
    @cython.locals(a=cython.int, b=cython.int)
172
173
174
175
176
177
178
179
180
181
182
    def next_comment() -> Tuple[int, int]:
        nonlocal rest, comments
        if comments:
            try:
                m = next(comments)
                a, b = m.span()
                return rest.index(a), rest.index(b)
            except StopIteration:
                comments = None
        return -1, -2

183
184
185
186
    @cython.locals(start=cython.int)
    def str_search(s, start: int = 0) -> Tuple[int, int]:
        nonlocal rest
        return rest.find(s, start, start + search_window), len(s)
187

eckhart's avatar
eckhart committed
188
    @cython.locals(start=cython.int, end=cython.int)
189
190
    def rx_search(rx, start: int = 0) -> Tuple[int, int]:
        nonlocal rest
191
        m = rest.search(rx, start, start + search_window)
192
        if m:
193
194
            begin, end = m.span()
            return rest.index(begin), end - begin
195
196
        return -1, 0

197
198
199
200
    def algorithm_search(func: Callable, start: int = 0):
        nonlocal rest
        return func(rest, start)

eckhart's avatar
eckhart committed
201
    @cython.locals(a=cython.int, b=cython.int, k=cython.int, length=cython.int)
202
203
204
    def entry_point(search_func, search_rule) -> int:
        a, b = next_comment()
        k, length = search_func(search_rule)
eckhart's avatar
eckhart committed
205
        while a < b <= k + length:
206
            a, b = next_comment()
207
208
209
        # find next as long as start or end point of resume regex are inside a comment
        while (a < k < b) or (a < k + length < b):
            k, length = search_func(search_rule, b)
210
211
            while a < b <= k:
                a, b = next_comment()
212
        return k + length if k >= 0 else upper_limit
213

214
    # find closest match
Eckhart Arnold's avatar
Eckhart Arnold committed
215
    for rule in rules:
216
        comments = rest.finditer(comment_regex)
217
218
219
220
221
222
223
        if callable(rule):
            search_func = algorithm_search
        elif isinstance(rule, str):
            search_func = str_search
        else:
            search_func = rx_search
        pos = entry_point(search_func, rule)
224
        closest_match = min(pos, closest_match)
225

226
    # in case no rule matched return -1
227
228
229
    if closest_match == upper_limit:
        closest_match = -1
    return closest_match
Eckhart Arnold's avatar
Eckhart Arnold committed
230
231


232
233
234
235
236
237
238
########################################################################
#
# Parser base class
#
########################################################################


239
240
ApplyFunc = Callable[[List['Parser']], Optional[bool]]
        # The return value of `True` stops any further application
eckhart's avatar
eckhart committed
241
FlagFunc = Callable[[ApplyFunc, Set[ApplyFunc]], bool]
eckhart's avatar
eckhart committed
242
ParseFunc = Callable[[StringView], Tuple[Optional[Node], StringView]]
eckhart's avatar
eckhart committed
243
244


245
class Parser:
246
247
248
249
250
251
252
253
254
255
256
257
258
259
    """
    (Abstract) Base class for Parser combinator parsers. Any parser
    object that is actually used for parsing (i.e. no mock parsers)
    should should be derived from this class.

    Since parsers can contain other parsers (see classes UnaryOperator
    and NaryOperator) they form a cyclical directed graph. A root
    parser is a parser from which all other parsers can be reached.
    Usually, there is one root parser which serves as the starting
    point of the parsing process. When speaking of "the root parser"
    it is this root parser object that is meant.

    There are two different types of parsers:

di68kap's avatar
di68kap committed
260
    1. *Named parsers* for which a name is set in field `parser.pname`.
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
       The results produced by these parsers can later be retrieved in
       the AST by the parser name.

    2. *Anonymous parsers* where the name-field just contains the empty
       string. AST-transformation of Anonymous parsers can be hooked
       only to their class name, and not to the individual parser.

    Parser objects are callable and parsing is done by calling a parser
    object with the text to parse.

    If the parser matches it returns a tuple consisting of a node
    representing the root of the concrete syntax tree resulting from the
    match as well as the substring `text[i:]` where i is the length of
    matched text (which can be zero in the case of parsers like
    `ZeroOrMore` or `Option`). If `i > 0` then the parser has "moved
    forward".

    If the parser does not match it returns `(None, text). **Note** that
    this is not the same as an empty match `("", text)`. Any empty match
    can for example be returned by the `ZeroOrMore`-parser in case the
    contained parser is repeated zero times.

    Attributes and Properties:
284

285
286
        pname:  The parser's name or a (possibly empty) alias name in case
                of an anonymous parser.
287

288
289
290
291
292
        anonymous: A property indicating that the parser remains anynomous
                anonymous with respect to the nodes it returns. For performance
                reasons this is implemented as an object variable rather
                than a property. This property must always be equal to
                `self.tag_name[0] == ":"`.
293

294
295
296
297
        drop_content: A property (for performance reasons implemented as
                simple field) that, if set, induces the parser not to return
                the parsed content or sub-tree if it has matched but the
                dummy `EMPTY_NODE`. In effect the parsed content will be
298
299
300
                dropped from the concrete syntax tree already. Only
                anonymous (or pseudo-anonymous) parsers are allowed to
                drop content.
301

302
        tag_name: The tag_name for the nodes that are created by
303
304
                the parser. If the parser is named, this is the same as
                `pname`, otherwise it is the name of the parser's type.
305

306
307
308
309
310
311
312
313
314
315
        visited:  Mapping of places this parser has already been to
                during the current parsing process onto the results the
                parser returned at the respective place. This dictionary
                is used to implement memoizing.

        cycle_detection:  The apply()-method uses this variable to make
                sure that one and the same function will not be applied
                (recursively) a second time, if it has already been
                applied to this parser.

316
317
318
319
        proxied: The original `_parse()`-method is stored here, if a
                proxy (e.g. a tracing debugger) is installed via the
                `set_proxy()`-method.

320
        _grammar:  A reference to the Grammar object to which the parser
321
                is attached.
322
323
324
325
326

        _symbol:  The name of the closest named parser to which this
                parser is connected in a grammar. If pname is not the
                empty string, this will become the same as pname, when
                the property `symbol` is read for the first time.
327
328
    """

329
    def __init__(self) -> None:
330
        # assert isinstance(name, str), str(name)
331
        self.pname = ''               # type: str
332
        self.anonymous = True         # type: bool
333
        self.drop_content = False     # type: bool
334
335
        self.tag_name = self.ptype    # type: str
        self.cycle_detection = set()  # type: Set[ApplyFunc]
336
        # this indirection is required for Cython-compatibility
337
        self._parse_proxy = self._parse  # type: ParseFunc
eckhart's avatar
eckhart committed
338
        # self.proxied = None           # type: Optional[ParseFunc]
339
340
341
342
        try:
            self._grammar = GRAMMAR_PLACEHOLDER  # type: Grammar
        except NameError:
            pass
343
        self._symbol = ''             # type: str
344
345
346
        self.reset()

    def __deepcopy__(self, memo):
347
        """Deepcopy method of the parser. Upon instantiation of a Grammar-
348
        object, parsers will be deep-copied to the Grammar object. If a
349
        derived parser-class changes the signature of the `__init__`-constructor,
350
351
352
        `__deepcopy__`-method must be replaced (i.e. overridden without
        calling the same method from the superclass) by the derived class.
        """
353
        duplicate = self.__class__()
354
        copy_parser_base_attrs(self, duplicate)
355
        return duplicate
356

357
    def __repr__(self):
di68kap's avatar
di68kap committed
358
        return self.pname + self.ptype
359
360

    def __str__(self):
di68kap's avatar
di68kap committed
361
        return self.pname + (' = ' if self.pname else '') + repr(self)
362

363
364
365
366
367
368
    @property
    def ptype(self) -> str:
        """Returns a type name for the parser. By default this is the name of
        the parser class with an added leading colon ':'. """
        return ':' + self.__class__.__name__

369
370
371
372
373
    @property
    def symbol(self) -> str:
        """Returns the symbol with which the parser is associated in a grammar.
        This is the closest parser with a pname that contains this parser."""
        if not self._symbol:
eckhart's avatar
eckhart committed
374
375
376
377
378
379
            try:
                self._symbol = self.grammar.associated_symbol(self).pname
            except AttributeError:
                # return an empty string, if parser is not connected to grammar,
                # but be sure not to save the empty string in self._symbol
                return ''
380
381
        return self._symbol

382
383
384
    @property
    def repr(self) -> str:
        """Returns the parser's name if it has a name and self.__repr___() otherwise."""
di68kap's avatar
di68kap committed
385
        return self.pname if self.pname else self.__repr__()
386

387
388
389
390
    def reset(self):
        """Initializes or resets any parser variables. If overwritten,
        the `reset()`-method of the parent class must be called from the
        `reset()`-method of the derived class."""
391
        self.visited = dict()  # type: Dict[int, Tuple[Optional[Node], StringView]]
392

eckhart's avatar
eckhart committed
393
    @cython.locals(location=cython.int, gap=cython.int, i=cython.int)
394
395
396
    def __call__(self: 'Parser', text: StringView) -> Tuple[Optional[Node], StringView]:
        """Applies the parser to the given text. This is a wrapper method that adds
        the business intelligence that is common to all parsers. The actual parsing is
397
398
        done in the overridden method `_parse()`. This wrapper-method can be thought of
        as a "parser guard", because it guards the parsing process.
399
        """
400
        grammar = self._grammar
di68kap's avatar
di68kap committed
401
        location = grammar.document_length__ - text._len  # faster then len(text)?
402
403

        try:
404
405
            # rollback variable changing operation if parser backtracks
            # to a position before the variable changing operation occurred
406
            if grammar.last_rb__loc__ > location:
407
408
                grammar.rollback_to__(location)

409
            # if location has already been visited by the current parser, return saved result
410
411
            visited = self.visited  # using local variable for better performance
            if location in visited:
412
                # no history recording in case of memoized results!
413
                return visited[location]
414

415
416
417
            recursion_state = grammar.returning_from_recursion__
            grammar.returning_from_recursion__ = False

418
            # now, the actual parser call!
419
            try:
Eckhart Arnold's avatar
Eckhart Arnold committed
420
                node, rest = self._parse_proxy(text)
421
            except ParserError as pe:
422
                # catching up with parsing after an error occurred
423
                gap = len(text) - len(pe.rest)
di68kap's avatar
di68kap committed
424
                rules = grammar.resume_rules__.get(self.pname, [])
425
                rest = pe.rest[len(pe.node):]
426
427
                i = reentry_point(rest, rules, grammar.comment_rx__,
                                  grammar.reentry_search_window__)
428
                if i >= 0 or self == grammar.start_parser__:
eckhart's avatar
eckhart committed
429
430
                    # either a reentry point was found or the
                    # error has fallen through to the first level
431
                    assert pe.node.children or (not pe.node.result)
432
                    # apply reentry-rule or catch error at root-parser
eckhart's avatar
eckhart committed
433
                    if i < 0:  i = 0
434
                    try:
435
                        zombie = pe.node.pick_child(ZOMBIE_TAG)  # type: Optional[Node]
436
                    except (KeyError, ValueError):
437
438
439
                        zombie = None
                    if zombie and not zombie.result:
                        zombie.result = rest[:i]
eckhart's avatar
eckhart committed
440
                        tail = tuple()  # type: ChildrenType
441
442
                    else:
                        nd = Node(ZOMBIE_TAG, rest[:i]).with_pos(location)
eckhart's avatar
eckhart committed
443
                        # nd.attr['err'] = pe.error.message
444
                        tail = (nd,)
445
                    rest = rest[i:]
446
447
                    if pe.first_throw:
                        node = pe.node
448
                        node.result = node.children + tail
449
                    else:
450
451
                        node = Node(
                            self.tag_name,
di68kap's avatar
di68kap committed
452
453
                            (Node(ZOMBIE_TAG, text[:gap]).with_pos(location), pe.node) + tail) \
                            .with_pos(location)
eckhart's avatar
eckhart committed
454
                # if no re-entry point was found, do any of the following:
455
                elif pe.first_throw:
eckhart's avatar
eckhart committed
456
                    # just fall through
eckhart's avatar
eckhart committed
457
                    # TODO: Is this case still needed with module "trace"?
458
                    raise ParserError(pe.node, pe.rest, pe.error, first_throw=False)
459
                elif grammar.tree__.errors[-1].code == MANDATORY_CONTINUATION_AT_EOF:
eckhart's avatar
eckhart committed
460
461
                    # try to create tree as faithful as possible
                    node = Node(self.tag_name, pe.node).with_pos(location)
462
                else:
eckhart's avatar
eckhart committed
463
                    # fall through but skip the gap
464
465
                    result = (Node(ZOMBIE_TAG, text[:gap]).with_pos(location), pe.node) if gap \
                        else pe.node  # type: ResultType
466
467
                    raise ParserError(Node(self.tag_name, result).with_pos(location),
                                      text, pe.error, first_throw=False)
468

469
            if node is not None:
470
                node._pos = location
471
472
473
474
475
476
477
478
479
480
            if (grammar.memoization__
                    and not grammar.returning_from_recursion__
                    # variable-manipulating parsers will not be entered into the cache,
                    # because caching would interfere with changes of variable state
                    and grammar.last_rb__loc__ < location):
                visited[location] = (node, rest)

            if not grammar.returning_from_recursion__:
                grammar.returning_from_recursion__ = recursion_state

481
        except RecursionError as e:
482
            node = Node(ZOMBIE_TAG, str(text[:min(10, max(1, text.find("\n")))]) + " ...")
483
            node._pos = location
484
485
486
487
            error = Error("maximum recursion depth of parser reached; potentially due to too many "
                          "errors or left recursion!", location, RECURSION_DEPTH_LIMIT_HIT)
            grammar.tree__.add_error(node, error)
            grammar.most_recent_error__ = ParserError(node, text, error, first_throw=False)
488
489
490
            rest = EMPTY_STRING_VIEW

        return node, rest
491
492
493
494

    def __add__(self, other: 'Parser') -> 'Series':
        """The + operator generates a series-parser that applies two
        parsers in sequence."""
di68kap's avatar
di68kap committed
495
496
        if isinstance(other, Series):
            return cast('Series', other).__radd__(self)
497
498
499
500
501
502
        return Series(self, other)

    def __or__(self, other: 'Parser') -> 'Alternative':
        """The | operator generates an alternative parser that applies
        the first parser and, if that does not match, the second parser.
        """
di68kap's avatar
di68kap committed
503
504
        if isinstance(other, Alternative):
            return cast('Alternative', other).__ror__(self)
505
506
        return Alternative(self, other)

di68kap's avatar
di68kap committed
507
508
509
510
511
512
513
514
515
    def __mul__(self, other: 'Parser') -> 'Alternative':
        """The * operator generates an interleave parser that applies
        the first parser and the second parser in any possible order
        until both match.
        """
        if isinstance(other, Interleave):
            return cast(Interleave, other).__rmul__(self)
        return Interleave(self, other)

516
517
518
519
520
521
    def _parse(self, text: StringView) -> Tuple[Optional[Node], StringView]:
        """Applies the parser to the given `text` and returns a node with
        the results or None as well as the text at the position right behind
        the matching string."""
        raise NotImplementedError

eckhart's avatar
eckhart committed
522
523
524
525
526
527
528
    def is_optional(self) -> Optional[bool]:
        """Returns `True`, if the parser can never fails, i.e. never yields
        `None`, instead of a node. Returns `False`, if the parser can fail.
        Returns `None` if it is not known whether the parser can fail.
        """
        return None

529
    def set_proxy(self, proxy: Optional[ParseFunc]):
530
531
532
        """Sets a proxy that replaces the _parse()-method. Call `set_proxy`
        with `None` to remove a previously set proxy. Typical use case is
        the installation of a tracing debugger. See module `trace`.
533
534
        """
        if proxy is None:
Eckhart Arnold's avatar
Eckhart Arnold committed
535
            self._parse_proxy = self._parse
536
        else:
eckhart's avatar
eckhart committed
537
538
            if not isinstance(proxy, type(self._parse)):
                # assume that proxy is a function and bind it to self
539
540
                proxy = proxy.__get__(self, type(self))
            else:
eckhart's avatar
eckhart committed
541
                # if proxy is a method it must be a method of self
542
                assert proxy.__self__ == self
Eckhart Arnold's avatar
Eckhart Arnold committed
543
            self._parse_proxy = cast(ParseFunc, proxy)
544

545
    @property
eckhart's avatar
eckhart committed
546
    def grammar(self) -> 'Grammar':
547
        try:
eckhart's avatar
eckhart committed
548
            if self._grammar is not GRAMMAR_PLACEHOLDER:
549
550
                return self._grammar
            else:
eckhart's avatar
eckhart committed
551
                raise ValueError('Grammar has not yet been set!')
552
553
        except (AttributeError, NameError):
            raise AttributeError('Parser placeholder does not have a grammar!')
554
555
556

    @grammar.setter
    def grammar(self, grammar: 'Grammar'):
557
558
559
560
561
        try:
            if self._grammar == GRAMMAR_PLACEHOLDER:
                self._grammar = grammar
                # self._grammar_assigned_notifier()
            elif self._grammar != grammar:
eckhart's avatar
eckhart committed
562
563
                raise AssertionError("Parser has already been assigned"
                                     "to a different Grammar object!")
564
565
        except AttributeError:
            pass  # ignore setting of grammar attribute for placeholder parser
566
567
        except NameError:  # Cython: No access to GRAMMA_PLACEHOLDER, yet :-(
            self._grammar = grammar
568

eckhart's avatar
eckhart committed
569
    def sub_parsers(self) -> Tuple['Parser', ...]:
570
571
572
        """Returns the list of sub-parsers if there are any.
        Overridden by Unary, Nary and Forward.
        """
eckhart's avatar
eckhart committed
573
        return tuple()
574

575
    def _apply(self, func: ApplyFunc, context: List['Parser'], flip: FlagFunc) -> bool:
576
577
        """
        Applies function `func(parser)` recursively to this parser and all
578
579
        descendant parsers as long as `func()` returns `None` or `False`.
        Otherwise stops the further application of `func` and returns `True`.
eckhart's avatar
eckhart committed
580
581
582
583
584
585
586
587

        In order to break cycles, function `flip` is called, which should
        return `True`, if this parser has already been visited. If not, it
        flips the cycle detection flag and returns `False`.

        This is a protected function and should not called from outside
        class Parser or any of its descendants. The entry point for external
        calls is the method `apply()` without underscore!
588
        """
589
590
        if not flip(func, self.cycle_detection):
            if func(context + [self]):
591
592
593
                return True
            else:
                for parser in self.sub_parsers():
594
                    if parser._apply(func, context + [self], flip):
595
596
597
                        return True
                return False
        return False
598

599
    def apply(self, func: ApplyFunc) -> bool:
eckhart's avatar
eckhart committed
600
601
        """
        Applies function `func(parser)` recursively to this parser and all
602
603
604
605
606
607
608
609
610
611
612
613
614
615
        descendant parsers as long as `func()` returns `None` or `False`.
        Traversal is pre-order. Stops the further application of `func` and
        returns `True` once `func` has returned `True`.

        If `func` has been applied to all descendant parsers without issuing
        a stop signal by returning `True`, `False` is returned.

        This use of the return value allows to use the `apply`-method both
        to issue tests on all descendant parsers (including self) which may be
        decided already after some parsers have been visited without any need
        to visit further parsers. At the same time `apply` can be used to simply
        `apply` a procedure to all descendant parsers (including self) without
        worrying about forgetting the return value of procedure, because a
        return value of `None` means "carry on".
eckhart's avatar
eckhart committed
616
        """
Eckhart Arnold's avatar
Eckhart Arnold committed
617
        def positive_flip(f: Callable[['Parser'], None], flagged: Set[Callable]) -> bool:
eckhart's avatar
eckhart committed
618
619
620
621
622
623
624
625
626
            """Returns True, if function `f` has already been applied to this
            parser and sets the flag accordingly. Interprets `f in flagged == True`
            as meaning that `f` has already been applied."""
            if f in flagged:
                return True
            else:
                flagged.add(f)
                return False

Eckhart Arnold's avatar
Eckhart Arnold committed
627
        def negative_flip(f: Callable[['Parser'], None], flagged: Set[Callable]) -> bool:
eckhart's avatar
eckhart committed
628
629
630
631
632
633
634
635
636
637
            """Returns True, if function `f` has already been applied to this
            parser and sets the flag accordingly. Interprets `f in flagged == False`
            as meaning that `f` has already been applied."""
            if f not in flagged:
                return True
            else:
                flagged.remove(f)
                return False

        if func in self.cycle_detection:
638
            return self._apply(func, [], negative_flip)
eckhart's avatar
eckhart committed
639
        else:
640
            return self._apply(func, [], positive_flip)
641

642
    def static_error(self, msg: str, code: ErrorCode) -> 'AnalysisError':
643
        return (self.symbol, self, Error(msg, 0, code))
644

eckhart's avatar
eckhart committed
645
    def static_analysis(self) -> List['AnalysisError']:
646
647
        """Analyses the parser for logical errors after the grammar has been
        instantiated."""
eckhart's avatar
eckhart committed
648
        return []
eckhart's avatar
eckhart committed
649

650

651
652
def copy_parser_base_attrs(src: Parser, duplicate: Parser):
    """Duplicates all attributes of the Parser-class from source to dest."""
Eckhart Arnold's avatar
Eckhart Arnold committed
653
654
655
656
657
658
    duplicate.pname = src.pname
    duplicate.anonymous = src.anonymous
    duplicate.drop_content = src.drop_content
    duplicate.tag_name = src.tag_name


eckhart's avatar
eckhart committed
659
660
def Drop(parser: Parser) -> Parser:
    """Returns the parser with the `parser.drop_content`-property set to `True`."""
Eckhart Arnold's avatar
Eckhart Arnold committed
661
    assert parser.anonymous, "Parser must be anonymous to be allowed to drop ist content."
eckhart's avatar
eckhart committed
662
663
664
    if isinstance(parser, Forward):
        cast(Forward, parser).parser.drop_content = True
    parser.drop_content = True
Eckhart Arnold's avatar
Eckhart Arnold committed
665
    return parser
eckhart's avatar
eckhart committed
666
667


668
PARSER_PLACEHOLDER = Parser()
669
670


eckhart's avatar
eckhart committed
671
672
673
674
675
def is_parser_placeholder(parser: Optional[Parser]) -> bool:
    """Returns True, if `parser` is `None` or merely a placeholder for a parser."""
    return not parser or parser.ptype == ":Parser"


eckhart's avatar
eckhart committed
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
# functions for analysing the parser tree/graph ###


def has_non_autocaptured_symbols(context: List[Parser]) -> Optional[bool]:
    """Returns True, if the context contains a Capture-Parser that is not
    shielded by a Retrieve-Parser. This is the case for captured symbols
    that are not "auto-captured" by a Retrieve-Parser.
    """
    for parser in context:
        if parser.ptype == ":Retrieve":
            break
        elif parser.ptype == ":Capture":
            p = cast(UnaryParser, parser).parser
            while p.ptype in (":Synonym", ":Forward"):
                p = cast(UnaryParser, p).parser
            if not isinstance(p, Retrieve):
                return True
    return None


696
697
698
699
700
701
########################################################################
#
# Grammar class, central administration of all parser of a grammar
#
########################################################################

702
703
def mixin_comment(whitespace: str, comment: str) -> str:
    """
704
    Returns a regular expression pattern that merges comment and whitespace
705
    regexps. Thus comments can occur wherever whitespace is allowed
706
707
708
709
710
711
    and will be skipped just as implicit whitespace.

    Note, that because this works on the level of regular expressions,
    nesting comments is not possible. It also makes it much harder to
    use directives inside comments (which isn't recommended, anyway).
    """
712
    if comment:
eckhart's avatar
eckhart committed
713
714
        whitespace = '(?:' + whitespace + ')'
        comment = '(?:' + comment + ')'
715
716
        return '(?:' + whitespace + '(?:' + comment + whitespace + ')*)'
    return whitespace
717
718


di68kap's avatar
di68kap committed
719
def mixin_nonempty(whitespace: str) -> str:
Eckhart Arnold's avatar
Eckhart Arnold committed
720
    r"""
721
722
723
    Returns a regular expression pattern that matches only if the regular
    expression pattern `whitespace` matches AND if the match is not empty.

di68kap's avatar
di68kap committed
724
725
    If `whitespace`  does not match the empty string '', anyway,
    then it will be returned unaltered.
726
727
728
729
730
731
732
733
734

    WARNING: `non_empty_ws` does not work regular expressions the matched
    strings of which can be followed by a symbol that can also occur at
    the start of the regular expression.

    In particular, it does not work for fixed size regular expressions,
    that ist / / or /   / or /\t/ won't work, but / */ or /\s*/ or /\s+/
    do work. There is no test for this. Fixed sizes regular expressions
    run through `non_empty_ws` will not match at any more if they are applied
Eckhart Arnold's avatar
Eckhart Arnold committed
735
736
737
738
739
    to the beginning or the middle of a sequence of whitespaces!

    In order to be safe, you whitespace regular expressions should follow
    the rule: "Whitespace cannot be followed by whitespace" or "Either
    grab it all or leave it all".
740
741
742
743
744
745
746
747
748
749

    :param whitespace: a regular expression pattern
    :return: new regular expression pattern that does not match the empty
        string '' any more.
    """
    if re.match(whitespace, ''):
        return r'(?:(?=(.|\n))' + whitespace + r'(?!\1))'
    return whitespace


750
class UnknownParserError(KeyError):
eckhart's avatar
eckhart committed
751
    """UnknownParserError is raised if a Grammar object is called with a
752
    parser that does not exist or if in the course of parsing a parser
eckhart's avatar
eckhart committed
753
    is referred to that does not exist."""
754
755


756
757
AnalysisError = Tuple[str, Parser, Error]      # pname, parser, error
# TODO: replace with a named tuple?
758
759
760
761
762
763


class GrammarError(Exception):
    """GrammarError will be raised if static analysis reveals errors
    in the grammar.
    """
764
    def __init__(self, static_analysis_result: List[AnalysisError]):
765
766
767
768
769
770
771
772
773
774
        assert static_analysis_result  # must not be empty
        self.errors = static_analysis_result

    def __str__(self):
        if len(self.errors) == 1:
            return str(self.errors[0][2])
        return '\n' + '\n'.join(("%i. " % (i + 1) + str(err_tuple[2]))
                                for i, err_tuple in enumerate(self.errors))


775
776
777
778
779
780
781
782
783
784
785
786
787
class Grammar:
    r"""
    Class Grammar directs the parsing process and stores global state
    information of the parsers, i.e. state information that is shared
    accross parsers.

    Grammars are basically collections of parser objects, which are
    connected to an instance object of class Grammar. There exist two
    ways of connecting parsers to grammar objects: Either by passing
    the root parser object to the constructor of a Grammar object
    ("direct instantiation"), or by assigning the root parser to the
    class variable "root__" of a descendant class of class Grammar.

eckhart's avatar
eckhart committed
788
    Example for direct instantiation of a grammar::
789

790
        >>> number = RE(r'\d+') + RE(r'\.') + RE(r'\d+') | RE(r'\d+')
791
792
793
794
795
796
797
798
799
800
801
802
803
804
        >>> number_parser = Grammar(number)
        >>> number_parser("3.1416").content
        '3.1416'

    Collecting the parsers that define a grammar in a descendant class of
    class Grammar and assigning the named parsers to class variables
    rather than global variables has several advantages:

    1. It keeps the namespace clean.

    2. The parser names of named parsers do not need to be passed to the
       constructor of the Parser object explicitly, but it suffices to
       assign them to class variables, which results in better
       readability of the Python code.
805
       See classmethod `Grammar._assign_parser_names__()`
806
807

    3. The parsers in the class do not necessarily need to be connected
808
809
       to one single root parser, which is helpful for testing and when
       building up a parser gradually from several components.
810
811
812
813
814
815
816

    As a consequence, though, it is highly recommended that a Grammar
    class should not define any other variables or methods with names
    that are legal parser names. A name ending with a double
    underscore '__' is *not* a legal parser name and can safely be
    used.

817
    Example::
818
819
820
821
822
823
824
825
826

        class Arithmetic(Grammar):
            # special fields for implicit whitespace and comment configuration
            COMMENT__ = r'#.*(?:\n|$)'  # Python style comments
            wspR__ = mixin_comment(whitespace=r'[\t ]*', comment=COMMENT__)

            # parsers
            expression = Forward()
            INTEGER = RE('\\d+')
827
828
829
            factor = INTEGER | TKN("(") + expression + TKN(")")
            term = factor + ZeroOrMore((TKN("*") | TKN("/")) + factor)
            expression.set(term + ZeroOrMore((TKN("+") | TKN("-")) + term))
830
831
832
833
            root__ = expression

    Upon instantiation the parser objects are deep-copied to the
    Grammar object and assigned to object variables of the same name.
834
835
836
837
838
    For any parser that is directly assigned to a class variable the
    field `parser.pname` contains the variable name after instantiation
    of the Grammar class. The parser will never the less remain anonymous
    with respect to the tag names of the nodes it generates, if its name
    is matched by the `anonymous__` regular expression.
839
    If one and the same parser is assigned to several class variables
840
    such as, for example, the parser `expression` in the example above,
841
    which is also assigned to `root__`, the first name sticks.
842
843
844
845
846
847
848
849
850
851
852
853

    Grammar objects are callable. Calling a grammar object with a UTF-8
    encoded document, initiates the parsing of the document with the
    root parser. The return value is the concrete syntax tree. Grammar
    objects can be reused (i.e. called again) after parsing. Thus, it
    is not necessary to instantiate more than one Grammar object per
    thread.

    Grammar classes contain a few special class fields for implicit
    whitespace and comments that should be overwritten, if the defaults
    (no comments, horizontal right aligned whitespace) don't fit:

854
    Class Attributes:
855
856
857
858
        root__:  The root parser of the grammar. Theoretically, all parsers of the
                 grammar should be reachable by the root parser. However, for testing
                 of yet incomplete grammars class Grammar does not assume that this
                 is the case.
859

860
861
862
        resume_rules__: A mapping of parser names to a list of regular expressions
                that act as rules to find the reentry point if a ParserError was
                thrown during the execution of the parser with the respective name.
Eckhart Arnold's avatar
Eckhart Arnold committed
863

864
865
866
867
868
        anonymous__: A regular expression to identify names of parsers that are
                assigned to class fields but shall never the less yield anonymous
                nodes (i.e. nodes the tag name of which starts with a colon ":"
                followed by the parser's class name). The default is to treat all
                parsers starting with an underscore as anonymous in addition to those
869
870
                parsers that are not directly assigned to a class field.

eckhart's avatar
eckhart committed
871
        parser_initialization__:  Before the grammar class (!) has been initialized,
872
                 which happens upon the first time it is instantiated (see
873
                 `:func:_assign_parser_names()` for an explanation), this class
874
875
                 field contains a value other than "done". A value of "done" indicates
                 that the class has already been initialized.
876

877
878
879
880
881
882
883
        static_analysis_pending__: True as long as no static analysis (see the method
                with the same name for more information) has been done to check
                parser tree for correctness. Static analysis
                is done at instantiation and the flag is then set to false, but it
                can also be carried out once the class has been generated
                (by DHParser.ebnf.EBNFCompiler) and then be set to false in the
                definition of the grammar class already.
884

885
886
887
        static_analysis_errors__: A list of errors and warnings that were found in the
                static analysis

eckhart's avatar
eckhart committed
888
889
890
891
        python__src__:  For the purpose of debugging and inspection, this field can
                 take the python src of the concrete grammar class
                 (see `dsl.grammar_provider`).

892
    Instance Attributes:
893
894
        all_parsers__:  A set of all parsers connected to this grammar object

895
896
        comment_rx__:  The compiled regular expression for comments. If no
                comments have been defined, it defaults to RX_NEVER_MATCH
897
898
                This instance-attribute will only be defined if a class-attribute
                with the same name does not already exist!
899

eckhart's avatar
eckhart committed
900
901
902
903
        start_parser__:  During parsing, the parser with which the parsing process
                was started (see method `__call__`) or `None` if no parsing process
                is running.

904
905
906
907
908
909
910
        _dirty_flag__:  A flag indicating that the Grammar has been called at
                least once so that the parsing-variables need to be reset
                when it is called again.

        document__:  the text that has most recently been parsed or that is
                currently being parsed.

eckhart's avatar
eckhart committed
911
912
        document_length__:  the length of the document.

913
914
        document_lbreaks__ (property):  list of linebreaks within the document,
                starting with -1 and ending with EOF. This helps generating line
915
                and column number for history recording and will only be
916
                initialized if :attr:`history_tracking__` is true.
917

918
919
920
921
922
        tree__: The root-node of the parsing tree. This variable is available
               for error-reporting already during parsing  via
               ``self.grammar.tree__.add_error``, but it references the full
               parsing tree only after parsing has been finished.

923
        _reversed__:  the same text in reverse order - needed by the `Lookbehind`-
924
925
926
                parsers.

        variables__:  A mapping for variable names to a stack of their respective
927
928
                string values - needed by the :class:`Capture`-, :class:`Retrieve`-
                and :class:`Pop`-parsers.
929
930

        rollback__:  A list of tuples (location, rollback-function) that are
931
932
933
934
                deposited by the :class:`Capture`- and :class:`Pop`-parsers.
                If the parsing process reaches a dead end then all
                rollback-functions up to the point to which it retreats will be
                called and the state of the variable stack restored accordingly.
935
936
937

        last_rb__loc__:  The last, i.e. most advanced location in the text
                where a variable changing operation occurred. If the parser
938
939
                backtracks to a location at or before last_rb__loc__ (i.e.
                location <= last_rb__loc__) then a rollback of all variable
940
941
                changing operations is necessary that occurred after the
                location to which the parser backtracks. This is done by
942
                calling method :func:`rollback_to__(location)`.
943

944
945
946
947
948
949
950
        returning_from_recursion__: A flag that is true if - during parsing -
                a parser returns from a recursive call, in which case its
                results should not be memoized, because it might be tried
                again with an increased recursion depth. This flag is needed by
                the left-recursion handling algorithm. See `Parser.__call__`
                ans `Forward.__call__`.

951
952
953
954
955
        memoization__:  Turns full memoization on or off. Turning memoization off
                results in less memory usage and sometimes reduced parsing time.
                In some situations it may drastically increase parsing time, so
                it is safer to leave it on. (Default: on)

956
957
958
959
960
961
962
963
964
965
966
        # mirrored class attributes:

        static_analysis_pending__: A pointer to the class attribute of the same name.
                (See the description above.) If the class is instantiated with a
                parser, this pointer will be overwritten with an instance variable
                that serves the same function.

        static_analysis_errors__: A pointer to the class attribute of the same name.
                (See the description above.) If the class is instantiated with a
                parser, this pointer will be overwritten with an instance variable
                that serves the same function.
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986

        # tracing and debugging support

        # These parameters are needed by the debugging functions in module
        # `trace.py`. They should not be manipulated by the users of class
        #  Grammar directly.

        history_tracking__:  A flag indicating that the parsing history is
                being tracked. This flag should not be manipulated by the
                user. Use `trace.set_tracer(grammar, trace.trace_history)` to
                turn (full) history tracking on and
                `trace.set_tracer(grammar, None)` to turn it off. Default is off.

        resume_notices__: A flag indicating that resume messages are generated
                in addition to the error messages, in case the parser was able
                to resume after an error. Use `trace.resume_notices(grammar)` to
                turn resume messages on and `trace.set_tracer(grammar, None)`
                to turn resume messages (as well as history recording) off.
                Default is off.

di68kap's avatar
di68kap committed
987
988
989
        call_stack__:  A stack of the tag names and locations of all parsers
                in the call chain to the currently processed parser during
                parsing. The call stack can be thought of as a breadcrumb trail.
990
                This is required for recording the parser history (for debugging)
991
992
993
                and, eventually, i.e. one day in the future, for tracing through
                the parsing process.

994
995
996
997
        history__:  A list of history records. A history record is appended to
                the list each time a parser either matches, fails or if a
                parser-error occurs. See class `log.HistoryRecord`. History
                records store copies of the current call stack.
998
999

        moving_forward__: This flag indicates that the parsing process is currently
1000
                moving forward. It is needed to reduce noise in history recording